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Analytica Chimica Acta (v.557, #1-2)

Outside front cover - Editorial Board (pp. co1).

Contents (pp. vii-ix).

Calendar of forthcoming meetings (pp. n1).

Preface by Peter Schoenmakers; Robert Smits (pp. 1-1).

Characterisation of hydroxypropylmethylcellulose phthalate (HPMCP) by GPC using a modified organic solvent by Elizabeth Meehan (pp. 2-6).

Hydroxypropylmethylcellulose phthalate (HPMCP) is readily soluble in a number of organic solvents which could be used as eluent in gel permeation chromatography (GPC) for the determination of polymer molecular weight distribution (MWD). GPC analysis performed using acetone as the mobile phase indicated a strong interaction between the polymer and the column packing material. GPC analysis performed using tetrahydrofuran (THF) as the mobile phase also indicated that there was some sample to column interaction although it was much weaker than that observed with acetone. It was found that the anomalous behaviour of HPMCP in THF could be suppressed by the addition of 5% acetic acid. This modified eluent system was used to characterise the MWD of a number of different batches of HPMCP by GPC with multiple detection. A good correlation was observed between the viscosity values quoted by the supplier and the average molecular weight values determined by GPC, although the GPC analysis revealed some differences in polydispersity. The effect of storage conditions on the MWD of HPMCP was also studied.

Keywords: Hydroxypropylmethylcellulose phthalate; HPMCP; GPC; Molecular weight distribution; Degradation

Effect of calibration standards on the quantification of hydroxy products from can coatings by S. Pastorelli; G. Beld�; C. Simoneau (pp. 7-10).

A liquid chromatographic (LC) method for Bisphenol A diglycidyl ether (BADGE), Bisphenol F diglycidyl ether (BFDGE) and their derivatives is currently being validated at the level of European Committee for Standardisation (CEN). The method consists in hydrolysing the substances to their di-hydroxy forms with a quantification based on calibration using hydrolysed monomers (BADGE�2H₂O or BFDGE�2H₂O). Considering laboratories may be tempted to use standards of BADGE�2H₂O or BFDGE�2H₂O now commercially available instead of performing the hydrolysis described, a comparison was made on the effect of using a calibration based on the commercial hydrolysis product versus hydrolysing the monomer on the quantification of the migration limit for enforcement purposes. In this work, the epoxy bis (diol) derivatives were quantified in three different food simulants.

Keywords: Liquid chromatography; Fluorescence; Bisphenol A diglycidyl ether dihydroxy derivatives; Bisphenol F diglycidyl ether dihydroxy derivatives; Food simulants; Calibration

Slow analyte diffusion effects on the A-term band broadening in macromolecular liquid chromatography separations by J. Billen; P. Gzil; J. De Smet; N. Vervoort; G. Desmet (pp. 11-18).

Computational methods have been used to study the effect of the molecular diffusivity of analytes on the band broadening and more particular the A-term band broadening, in liquid chromatography. The study was conducted on a two-dimensional mimic of a packed bed with nonporous particles ( k″=0) and on a hypothetical perfectly ordered packed bed. The advantage of this computational approach is that the molecular diffusion coefficient of the solute in the mobile phase can be varied freely without affecting other parameters. The considered systems hence also formed a perfect test case for Giddings reduced plate height data representation method. The fact that the plate height values for the different D_mol-cases were found to fall exactly on the same single reduced plate height curve hence simultaneously validates Giddings (undisputed) theory and the presently proposed method of chromatographic data simulation. The obtained results are also ideally suited for plate height model discrimination, because they yield highly accurate band broadening data (devoid of any experimental scatter) over a very broad range of reduced velocities ( ν up to 9000). The best agreement between simulation data and theory is found for the Knox model in which the Knox coefficient was lowered from the widely used n=1/3 to a value of n=0.23. This value agrees well with recent data obtained by Popovici et al. in experimental plate height studies of size exclusion chromatography (SEC) of polymers in a range of reduced velocities amounting up to nearly ν=10⁵.

Keywords: Liquid chromatography; Band broadening; Molecular diffusivity; Computational fluid dynamics

The microstructure of poly(butylene terephthalate) copolymers via¹³C NMR sequence distribution analysis: Solid-state copolymerization versus melt copolymerization by M.A.G. Jansen; J.G.P. Goossens; G. de Wit; C. Bailly; C.E. Koning (pp. 19-30).

Two diols, 2,2-bis(4-[hydroxyethoxy]phenyl)propane (Dianol 220^®) and bis(2-hydroxyethyl)terephthalate (BHET), were incorporated into poly(butylene terephthalate) (PBT) by solid-state polymerization (SSP) and melt polymerization (MP). Different PBT/diol ratios were used to obtain copolymers with different compositions.¹³C NMR spectroscopy was used to analyze the sequence distribution and the data analysis was discussed in detail. Both Dianol and BHET were randomly incorporated in the MP copolymers. For both PBT–Dianol and PBT–BHET copolymers obtained via SSP, a non-random, blocky microstructure was obtained. For the PBT–Dianol copolymers, the randomness increased for increased fractions of incorporated Dianol. For the PBT–BHET copolymers, the randomness continuously decreased with increased fractions of incorporated BHET.

Keywords: ¹³; C NMR sequence distribution analysis; Polycondensation; PBT; Microstructure

Characterization of alkyd resins by size exclusion chromatography coupled with a multi-angle light scattering photometer by Daniela Vareckova; Stepan Podzimek; Jan Lebduska (pp. 31-36).

An on-line multi-angle light scattering detector (MALS) coupled with size exclusion chromatography (SEC) has been used for the determination of molar mass and size distribution of alkyd resins. Molar mass distribution of alkyd resins is usually determined by SEC using calibration by polystyrene standards (PS). Since the molecules of alkyd resins are significantly more compact than those of linear polystyrene the molar mass determined by conventional SEC is incorrect. The correct molar mass can be obtained using an on-line MALS detector that eliminates the column calibration. In addition, it allows sample differentiation in respect to their degree of branching. It was found that highly branched alkyd molecules have abnormal elution behavior.

Keywords: Alkyd resin; Size exclusion chromatography; Multi angle light scattering; Molar mass; Branching

Coulometric generation of acids and bases for acid–base titrations in non-aqueous solvents by R.P. Mihajlović; Lj.N. Jakšić; R.M. Džudović (pp. 37-44).

A literature review of compounds which on electro-oxidation or reduction produce a strong acid or strong base in non-aqueous solvents is presented in this paper. The application of these compounds as anodic or cathodic depolarizers for coulometric titrations of acids, bases and salts as well as for the study of acid–base equilibria in non-aqueous solvents is also covered.

Keywords: Generation of acids and bases; Depolarizers; Coulometric titration; Acid–base constants; Non-aqueous solvents

Self-assembled monolayer modified gold electrodes for traces Cu(II) determination by A. Profumo; D. Merli; M. Pesavento (pp. 45-51).

d,l-Penicillamine and thiodimethylglyoxime (TDMG) self-assembled monolayers (SAMs) on gold electrode were prepared and characterized by electrochemical measurements. The two sensors exhibit sensitive and selective response to Cu(II), both forming 2:1 complexes, the first one in acetic buffer and the second one in ammonia buffer.Copper determination at trace level (LOQ 0.2 and 0.3μg/L ford,l-penicillamine and TDMG, respectively) is possible with both the electrodes as verified in tap, spring and sea water. The influence on copper determination of most common ions present in natural waters and of organic matter has been investigated. Accuracy was checked by recovery test on spiked samples.

Keywords: Self-assembled monolayers; d; ,; l; -Penicillamine SAM; Thiodimethylglyoxime SAM; Cu determination; Adsorptive stripping analysis

Electrocatalytic oxidation and sensitive detection of cysteine at layer-by-layer assembled carbon nanotube-modified electrode by Xu Chen; Yi Yang; Mingyu Ding (pp. 52-56).

Electrocatalytic oxidation of cysteine (CySH) at multilayer films of carbon nanotube (CNT)-modified electrode was studied. The CNT-modified electrode was fabricated through layer-by-layer electrostatic deposition of positively charged poly(diallyldimethylammonium chloride) (PDDA) and negatively charged shortened multi-walled carbon nanotubes (MWNTs) on glassy carbon (GC) electrode surface. The multilayer film was characterized by scanning electron microscopy and cyclic voltammetry. Effect of scan rate on CySH oxidation was also investigated. Sensitive detection for CySH at (PDDA/MWNT)₅/GC electrode in 0.16molL⁻¹ phosphate buffer solution (pH 7.4) was carried out. A linear calibration curve was observed in the range of 20μmolL⁻¹ to 1.3mmolL⁻¹ with differential pulse voltammetry (DPV). The detection limit (signal/noise, 3) of 0.3μmolL⁻¹ was obtained at 0.8V in steady-current response.

Keywords: Carbon nanotubes; Layer-by-layer; Cysteine; Electrocatalytic oxidation

Bismuth film microelectrode for direct voltammetric measurement of trace cobalt and nickel in some simulated and real body fluid samples by Emily A. Hutton; Božidar Ogorevc; Samo B. Ho�?evar; Malcolm R. Smyth (pp. 57-63).

The bismuth film microelectrode (BiFME), consisting of a bismuth film ex situ preplated onto a single carbon fibre substrate microelectrode, is presented for the direct simultaneous determination of trace Co(II) and Ni(II) in selected low-volume simulated and real human body fluid samples, using the adsorptive cathodic stripping voltammetric (AdCSV) protocol with dimethylglyoxime (DMG) as complexing agent. The BiFME exhibited well-defined and undistorted current signals for the Co(II) and Ni(II) ions, with the signals for each metal being independent of each other. Factors influencing the stripping performance at BiFME, including complexing agent concentration, accumulation potential and time, were examined. The stripping performance of the BiFME for simultaneous measurement of Co(II) and Ni(II), in the presence of dissolved oxygen, is characterised by very low detection limits of 69ng/L (1.2×10⁻⁹M) for Co(II) and 56ng/L (9.5×10⁻¹⁰M) for Ni(II) employing a preconcentration time of only 60s, good linearity ( r>0.995), and excellent reproducibility with relative standard deviations of 4.6% and 3.8% for 0.5μg/L ( n=10) of Co(II) and Ni(II), respectively. The applicability of the BiFME in direct measurement of trace Co(II) and Ni(II) in some simulated (saliva, sweat) and real (aqueous humor, cerebrospinal fluid) unpretreated low-volume (100–225μL) biological fluids is demonstrated. The attractive behaviour of the new “mercury-free�? BiFME microsensor augurs well for its use in the monitoring of Co(II) and Ni(II) release from customarily employed biomedical devices and routinely encountered metallic items, and for its deployment in clinical testing of biological fluids for cobalt and nickel exposure from medical implants.

Keywords: Bismuth film microelectrode; Cobalt; Nickel; Adsorptive stripping voltammetry; Saliva; Sweat; Aqueous humor; Cerebrospinal fluid

Voltammetric determination of 6-benzylaminopurine (6-BAP) using an acetylene black-dihexadecyl hydrogen phosphate composite film coated glassy carbon electrode by Dong Sun; Huajie Zhang (pp. 64-69).

An acetylene black-dihexadecyl hydrogen phosphate (denoted as AB-DHP) composite film coated glassy carbon electrode (GCE) is described for the determination of 6-benzylaminopurine (6-BAP). The electrochemical behavior of 6-BAP was investigated using cyclic voltammetry (CV), linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV). Compared with the unmodified GCE, the AB-DHP film-modified GCE remarkably enhances the oxidation peak current of 6-BAP, suggesting great potential in the determination of trace level of 6-BAP. All the experimental parameters such as supporting electrolyte, the volume of modifier (AB-DHP suspension), scan rate, and accumulation conditions, were optimized. Finally, a sensitive and simple voltammetric method with a good linear relationship in the range of 2.0×10⁻⁸ to 5.0×10⁻⁶mol/L, was developed for the determination of 6-BAP. The detection limit was also examined and a low value of 5.0×10⁻⁹mol/L for 5min accumulation was obtained. This newly proposed method was successfully applied to detect 6-BAP in practical samples.

Keywords: 6-Benzylaminopurine (6-BAP); Electrochemical detection; Acetylene black; Modified electrodes

Simultaneous square wave stripping voltammetric determination of platinum group metals (PGMs) and lead at trace and ultratrace concentration level by Clinio Locatelli (pp. 70-77).

The present work purposes two goals: to set up both a new method for simultaneously determining, at ultratrace level concentrations, Pd(II) and Rh(III) by square wave adsorption stripping voltammetry (SWAdSV), using dimethylglyoxime (DMG) as complexing agent, and a new analytical procedure for the sequential determination of Pt(II), Rh(III), Pd(II) by square wave adsorption stripping voltammetry (SWAdSV) and Pb(II) by square wave anodic stripping voltammetry (SWASV) in surface water.The critical comparison between peak area and peak current highlights once more that lower limits of detection are obtained if peak area is employed as instrumental datum.About 0.5mol/L acetate buffer pH 3.5+1.8�10⁴mol/L dimethylglyoxime (DMG), 0.3mol/L HCl and 0.6mmol/L formaldehyde+1.2mmol/L hydrazine (formazone complex) in 0.3mol/L HCl were employed as the supporting electrolytes.The analytical procedure was verified by the analysis of the standard reference materials: sea water BCR-CRM 403 and fresh water NIST-SRM 1643d. Precision and accuracy, expressed as relative standard deviation and relative error, respectively, were generally lower than 6% in all cases.Once set up on the standard reference materials, the analytical procedure was transferred and applied to surface water sampled in proximity to superhighway and in the Po river mouth area.A critical comparison with spectroscopic measurements is also disc used.

Keywords: Platinum metals group; Lead; Voltammetry; Atomic absorption spectrometry; Surface water; Dimethylglyoxime

A highly sensitive hydrogen peroxide amperometric sensor based on MnO₂ nanoparticles and dihexadecyl hydrogen phosphate composite film by Shaojun Yao; Junhui Xu; Ying Wang; Xiaoxia Chen; Yanxia Xu; Shengshui Hu (pp. 78-84).

A sensitive sensor for the determination of hydrogen peroxide (H₂O₂) was fabricated with MnO₂ nanoparticles (nano-MnO₂) and dihexadecyl hydrogen phosphate (DHP) composite film. The sensor exhibits high sensitivity, due to the enhanced oxidation of hydrogen peroxide (H₂O₂) at the MnO₂ nanoparticles and its uniform dispersion in DHP film. Amperometry was carried to determine the concentration of H₂O₂. The dependence of the response current on H₂O₂ concentration was explored under optimal conditions and an excellent linear concentration range of 1.2×10⁻⁷–2.0×10⁻³M with a substantially low detection limit of 8.0×10⁻⁸M was obtained. The proposed nano-MnO₂/DHP sensor has the feature of high sensitivity of 2.66×10⁵μAM⁻¹cm⁻². This sensor has been applied to measure the concentration of H₂O₂ in tooth paste and hair dye. According to the principle of Sensors with injectable recognition elements (SIRE), trace concentration of glucose in urine samples can also be calculated.

Keywords: Hydrogen peroxide sensor; Nano-MnO; ₂; DHP; Amperometry

New glucose biosensor based on a poly( o-phenylendiamine)/glucose oxidase-glutaraldehyde/Prussian blue/Au electrode with QCM monitoring of various electrode-surface modifications by Chunyan Deng; Mingrui Li; Qingji Xie; Meiling Liu; Yueming Tan; Xiahong Xu; Shouzhuo Yao (pp. 85-94).

The immobilization of glucose oxidase (GOD) via its dip-dry coating on a Prussian blue (PB) modified Au electrode followed by deposition of an outer poly( o-phenylenediamine) (P oPD) film and then glutaraldehyde (GA) cross-linking was investigated for amperometric glucose sensing, based on the reduction of enzymatically generated H₂O₂ catalyzed by the electroactive PB layer of the P oPD/GOD-GA/PB/Au electrode. The quartz crystal microbalance (QCM) was used to monitor various electrode-modification processes, and the effective enzymatic specific activity (ESA, defined as enzymatic activity per gram of enzyme) of immobilized GOD was estimated based on the mass of immobilized GOD (from QCM) and the quantity of hydrogen peroxide as the product of the enzymatic reaction (from amperometric detection) for the first time. The ESA of native GOD under our experimental conditions was also estimated via amperometric detection of enzymatically generated H₂O₂ at a PB-modified Au electrode. Effects of various experimental parameters on glucose sensing, including the applied potential, solution pH and electroactive interferents, were investigated. At an optimal potential of −0.05V versus saturated KCl calomel electrode (SCE), the current response of the biosensor in the selected phosphate buffer (pH 7.0) was linear with glucose concentration from 0.05 to 10mmolL⁻¹, with detection limit of 8μmolL⁻¹, short response time (within ∼5s) and good anti-interferent ability. The Michaelis constant(Kmapp) of the immobilized GOD was estimated as 19.6mmolL⁻¹. The biosensor exhibited good storage stability, i.e., 88% of its initial response was retained after 30-day storage in pH 7.0 phosphate buffer at 4°C. Since the present sensor-fabrication platform is rather general and advantageous in saving biochemical reagents, it is recommended for the development of other biosensors based on other substrate electrode materials, e.g. glassy carbon that has been tested in this work with satisfactory results.

Keywords: Amperometric glucose biosensor; Quartz crystal microbalance (QCM); Glucose oxidase; Poly(; o; -phenylenediamine); Prussian blue; Glutaraldehyde cross-linking; Enzymatic specific activities of immobilized and native GOD

Determination of thiabendazole residues in citrus fruits using a Multicommuted fluorescence-based optosensor by Juan F. Garc�a-Reyes; Eulogio J. Llorent-Mart�nez; Pilar Ortega-Barrales; Antonio Molina-D�az (pp. 95-100).

In this work, a method based on the combination of a multi-commuted flow system and solid-surface fluorescence spectroscopy has been developed and validated for the determination of thiabendazole residues in citrus fruits. The flow system was designed using three-way solenoid valves, controlled by Java-written home-made software, for independent automated manipulation of solutions. The native fluorescence signal of thiabendazole (using C₁₈ as solid support) was used for its quantitation in citrus extracts. The sample treatment involved a liquid–liquid extraction with acetonitrile followed by a clean-up step using primary–secondary amine. Using an optimized sampling time, the analytical signal showed linearity in the range 0.3–10mgkg⁻¹ with a detection limit of 0.09mgkg⁻¹ and obtaining R.S.D. (%) values better than 2% for both lemon and orange matrices. Recovery experiments accomplished on different citrus fruit samples at different concentrations yielded recoveries between 87.1 and 108.9%. The proposed method was satisfactorily applied to the analysis of thiabendazole in different citrus samples, obtaining remarkably good agreement with liquid chromatography–electrospray/mass spectrometry reference method.

Keywords: Thiabendazole; Pesticide; Optosensor; Multicommutation; Food analysis

Characteristics of immersion angle dependence of the resonant frequency shift of the quartz crystal microbalance in solutions by Minoru Yoshimoto; Shun-ichiro Yoshimura; Shigeru Kurosawa (pp. 101-105).

We investigated the immersion angle dependence of the resonant frequency shift (Δ F) of the quartz crystal microbalance (QCM) in a Newtonian liquid from the point of view of the QCM oscillation direction. In this paper, the three cases of immersion angles were employed. In , the angles of both the surface with the electrode ( x– z surface) and the QCM oscillation direction varied at the same time. In , the QCM oscillation direction changed while the x– z surface of the QCM was kept parallel to the gravity direction. In , the angle of the x– z surface of the QCM changed, while the QCM oscillation direction was constantly kept perpendicular to the gravity direction. This study elucidated that the Δ F values changed with the immersion angles in , and unchanged in . As a result, we have found that only when the x– z surface of the QCM is not parallel to the gravity direction, the immersion angle dependence of Δ F appears. Namely, it has become clear that the immersion angle dependence of Δ F has no relation to the QCM oscillation direction.

Keywords: QCM; Immersion angle; Oscillation direction

Real time kinetic analysis of the interaction between interleukin-1α and soluble interleukin-1 receptor I using a resonant mirror biosensor by Bao-Yan Wu; Jing Li; Jia-Dong Huang; Yan-Yan Wang; Hui-Jun Yin; Ke-Ji Chen; Qiang Chen (pp. 106-110).

A novel method for real time kinetic analysis of the interaction between IL-1α and sIL-1R I is reported. sIL-1R I was immobilized on the biotin cuvette surface of the resonant mirror biosensor to set up the experimental model. Results obtained from the assay confirmed that biotinylated sIL-1R I was specifically immobilized on the avidin-coated biotin cuvette surface, the interaction between IL-1α and sIL-1R I was fast and specific, and the interaction response is dose-dependence of IL-1α in solution with a range of 150–2400nM. The binding curve was fitted by FASTfit analysis, which fitted the monophasic association quite well, and the error did not exceed 0.4 arc seconds. Kinetic constants for IL-1α binding to sIL-1R I were determined from the plots of K_on versus the concentration of IL-1α. For the interaction, k_ass was 2.81×10³M⁻¹s⁻¹, K_diss was 2.52×10⁻³s⁻¹, and K_D was 8.97×10⁻⁷M.

Keywords: Interleukin-1α; Soluble interleukin-1 receptor I; Resonant mirror biosensor; Kinetic analysis

A low-cost optical sensing device based on paired emitter–detector light emitting diodes by King-Tong Lau; Susan Baldwin; Martina O’Toole; Roderick Shepherd; William J. Yerazunis; Shinichi Izuo; Satoshi Ueyama; Dermot Diamond (pp. 111-116).

A low-power, high sensitivity, very low-cost light emitting diode (LED)-based device for intensity-based light measurements is described. In this approach, a reverse-biased LED functioning as a photodiode is coupled with a second LED configured in conventional emission mode. A simple timer circuit measures how long (in microsecond) it takes for the photocurrent generated on the detector LED to discharge its capacitance from logic 1 (+5V) to logic 0 (+1.7V). The entire instrument provides an inherently digital output of light intensity measurements for a few cents. This light intensity dependent discharge process has been applied to measuring concentrations of coloured solutions and a mathematical model developed based on the Beer–Lambert Law.

Keywords: Light emitting diode; Photodiode; Colorimetry; Optical sensor; Sensor networks

Quantitative determination of heparin levels in serum with microtiter plate-format optode by Sung Bae Kim; Tae Young Kang; Geun Sig Cha; Hakhyun Nam (pp. 117-122).

A new assay method has been developed for the quantitative determination of heparin in serum using a microtiter plate-format optode (MPO). Heparin and proton in physiological sample are favorably co-extracted into the solvent polymeric optode membrane containing both cationic lipophilic additive, tridodecylmethyl ammonium chloride (TDMAC), and proton-selective ionophore, 3-hydroxy-4-(4-nitrophenylazo)-phenyloctadecanoate (ETH 2412), resulting in the absorbance change of the membrane to varying heparin levels. The optimized MPO composition contains low polymer-to-plasticizer ratio compared to those of conventional ion-selective optodes or electrodes, i.e., poly(vinyl chloride) (20.0)/dioctylsebacate (76.3)/ETH 2412 (1.7)/TDMAC (1.0) (wt.%): it resulted in a quantitative response to heparin from 0 to 15unit/mL in serum with high sensitivity. The heparin–protamine titration on the MPO could provide rapid and precise determination of heparin. It was shown that the heparin levels in serum sample could be determined from the rate of absorbance change over time (Δ A/Δ t); this method was more effective than the direct absorbance measurement in minimizing the interferences from color and turbidity of serum samples. MPO has been developed as a high throughput and convenient disposable sensing device, and may find a wide application in the determination of polyions and charged macromolecules.

Keywords: Microtiter plate-format optode; Heparin; Protamine; Polymer-to-plasticizer ratio; Ion-selective optode

Fiber optic based gas sensor with nanoporous structure for the selective detection of NO₂ in air samples by Shelly John Mechery; Jagdish P. Singh (pp. 123-129).

A fiber optic based sensor (FOS) system for the selective detection of NO₂ in air samples has been developed. In the present design, a signal transduction mechanism based on the spectroscopic changes at the nanopores of a sol–gel element has been utilized. The sensor is prepared by uniformly immobilizing NO₂ sensing reagents at the pores during the sol–gel process. This facilitates an easy tailoring of the transducer element to build different optical designs. In the present paper, we describe two different fiber optic sensor designs, which are operating in extrinsic and intrinsic configurations. The extrinsic design is based on the fiber optic transflection probe geometry with its sensor element placed at the distal end of the fiber bundle. A part per billion (ppb) level detection has been achieved with the intrinsic sensor design with an active sol–gel fiber core as a sensor element. The two different optical designs improve the NO₂ detection level and sensitivity of detection. The nitrogen dioxide mediated coloration reaction ensures the high specificity of detection when tested in a mixture of gas samples. The test results indicate the potential use of the fiber optic sensor for real time detection of NO₂ in air samples.

Keywords: Gas sensor; Fiber optic sensor; Nitrogen dioxide; Sol–gel

Microchip metal complex speciation: The nickel–bathophenanthroline disulfonic acid system by Karine Faure; Michael Loughran; Jeremy D. Glennon (pp. 130-136).

This is the first reported metal complex speciation of a single metal–ligand system by microchip electrophoresis. The nickel(II)–bathophenanthroline disulfonic acid system consists of three complexes with different stoichiometries, i.e., Ni(BPS)₁, Ni(BPS)₂ and Ni(BPS)₃. These nickel complexes are readily separated by capillary electrophoresis at 30kV, in 20mM sodium tetraborate at pH 9.3, 214nm UV detection. The identity of each Ni(II) complex species was confirmed by CE-ESI-MS. The three metal–complex species, in addition to the free ligand can be successfully separated on a 25mm quartz microchip with associated UV detection. Optimal electrophoretic parameters for efficient speciation of the nickel bathophenanthroline disulphonic acid complexes were: injection 1.0kV for 10s, separation 1.4kV for 13s in 10mM sodium tetraborate at pH 8.0, 214nm linear imaging UV detection. The influence of electrokinetic injection on the efficiency of metal speciation was also investigated.

Keywords: Speciation; Microchip electrophoresis; Stoichiometry; Nickel

Application of carbon nanotube-matrix assistant native polyacrylamide gel electrophoresis to the separation of apolipoprotein A-I and complement C3 by Guangming Huang; Yangjun Zhang; Jin Ouyang; Willy R.G. Baeyens; Joris R. Delanghe (pp. 137-145).

The application of carbon nanotube polyacrylamide gel electrophoresis (PAGE) is being reported so as to improve selectivity of analysis. A novel polyacrylamide gel was manufactured by adding multi-walled carbon nanotubes (MWNT) when producing the polyacrylamide gel. Carbon nanotube-matrix assistance was used to separate apolipoprotein A-I and complement C3 with native polyacrylamide gel electrophoresis. Significant improvement of the relative selectivity was achieved in the separation between apolipoprotein A-I and complement C3, because of the hydrophobic change of the carbon nanotube surface non-covalently functionalized by the surfactant Triton X-100. These two proteins were identified by MS/MS after electrophoresis. The change of the observed mobility can also be noticed using other nanomaterials such as nano-TiO₂ and nano-Al₂O_3, but no significant improvement of relative selectivities could be observed with the latter nanoparticles.

Keywords: Nanotube-matrix assistant; PAGE; Apolipoprotein A-I; Complement C3

Electrokinetically controlled real-time polymerase chain reaction in microchannel using Joule heating effect by Guoqing Hu; Qing Xiang; Rachel Fu; Bo Xu; Roberto Venditti; Dongqing Li (pp. 146-151).

In this work, a new method to control polymerase chain reaction (PCR) thermal cycling in a microchannel using Joule heating effect was presented. Joule heating was generated internally by the current flow through the buffer solution in an electrokinetically-driven microfluidic chip without external heater component. Numerical simulations were developed and conducted to determine the parameters required to achieve the desired thermal cycling. A PDMS-based microchannel PCR chip was fabricated and tested. The power consumption was only 1.3W for such a Joule heating-controlled PCR chip. To demonstrate the feasibility of using Joule heating to control thermal cycling, a DNA fragment of Escherichia coli O157:H7 stx1 was successfully amplified by a two-temperature TaqMan real-time polymerase chain reaction.

Keywords: Polymerase chain reaction (PCR); Microchannel; Joule heating

Magnetic bead-based chemiluminescence detection of sequence-specific DNA by using catalytic nucleic acid labels by Zhijuan Cao; Zengxi Li; Yujie Zhao; Yumin Song; Jianzhong Lu (pp. 152-158).

We wish to report a new chemiluminescence (CL) method for the determination of the sequence-specific DNA by the coupling of catalytic nucleic acid label (DNAzyme) based CL detection route with an efficient magnetic isolation of the hybrid. The assay relies on (i) the immobilization of NH₂-modified capture DNA on the surface of carboxyl-terminated magnetic beads activated by EDC, (ii) first hybridization event occurring between the bead-captured DNA probe and one 15-mer portion (5′-AAT ATT GAT AAG GAT-3′) of the target sequence, (iii) second hybridization happening between one part of the DNAzyme modified reporter sequence and another 15-mer portion (5′-GAG GGA TTA TTG TTA-3′) of the target sequence, and then direct detection of CL signal on the surface of the magnetic beads in a basic solution of luminol and H₂O₂. The influence of relevant experimental variables, including the effect of the amount of the magnetic beads, the duration of the hybridization and the parameters affecting CL signal, is examined and optimized. The results showed that this simple and sensitive protocol was suitable for the determination of specific-sequence DNA as exemplified by the 30-base sequence related to the anthrax lethal factor with a good linear correlation in the concentration range of 0.02–2pmol ( R²=0.9987) and a detection limit of 1×10⁻¹⁰M. Overall, this new CL protocol coupled the high sensitivity of CL analysis with effective magnetic separation for discriminating against unwanted constituents such as mismatched sequences and proteins, hence, offers great promise for DNA hybridization analysis.

Keywords: Catalytic nucleic acid label; Specific sequence DNA; Chemiluminescent; Magnetic beads

Cyclic accumulation of nanoparticles: A new strategy for electrochemical immunoassay based on the reversible reaction between dethiobiotin and avidin by Xun Mao; Jianhui Jiang; Jiwei Chen; Yong Huang; Guoli Shen; Ruqin Yu (pp. 159-163).

A new method based on cyclic accumulation of gold nanoparticles has been proposed for determinating human immunoglobulin G (IgG) by anodic stripping voltammetry. The dissociation reaction between dethiobiotin and avidin in the presence of biotin provides efficient means for the cyclic accumulation of gold nanoparticles used for the final analytical quantification. The immunoassay was conducted by following the typical procedure for sandwich-type immunoreaction. Goat anti-human IgG is immobilized on the wells of microtiter plates. The human IgG analyte is first captured by the primary antibody and then sandwiched by secondary antibody labeled with dethiobiotin. Avidin-Au solution was introduced to react with dethiobiotinylated antibody followed by adding of bioitin solution to wash it down. The dissociation of avidin-Au from dethiobiotinylated antibody was caused by displacing function of biotin to dethiobiotin. Making use of the ability of dethiobiotinylated antibody keeping its activity after the association/dissociation reaction, the alternatively treatment with avidin-Au and biotin solutions could realize cyclic accumulation of gold nanoparticles for ASV quantification. The anodic peak current increases gradually with the increasing accumulation cycles. Five cycles of accumulation are sufficient for the assay. The experiment conducted with a blank solution without addition of the analyte showed an extremely low background even with the number of accumulation cycles reached 10. The low background of the proposed method is a distinguished advantage providing a possibility for determination of at least 0.1ng/ml human IgG. The RSD of the method is 9.57% for eight times determination of 1ng/ml human IgG under the same conditions.

Keywords: Gold nanoparticle; Human IgG; Dethiobiotin; Anodic stripping voltammetry

Rapid time-resolved fluoroimmunoassay for the screening of monensin residues in eggs by Virve Hagren; Pekka Peippo; Mika Tuomola; Timo L�vgren (pp. 164-168).

Polyether ionophores, such as monensin, are commonly used as feed additives in the poultry production. However, ionophore residues in foodstuffs may have adverse health effects on humans. In order to effectively implement residue control programmes in the European Union (Council Directive 96/23/EC), rapid analysis methods are required. A competitive time-resolved fluoroimmunoassay was developed for the determination of monensin residues in eggs. Prior to analysis, the residues were extracted from eggs with acetonitrile according to a simple protocol. The assay, which could be utilised in a quantitative or qualitative mode, was validated in compliance with Commission Decision 2002/657/EC. The detection capability of the assay was determined to be less than 2μgkg⁻¹. The intra-assay variations ( n=6) were below 10% and the interassay variations ( n=18) ranged between 10.3 and 13.9%. The mean recoveries ( n=6), established at three concentration levels, varied from 88.0 to 102.1%.

Keywords: Polyether ionophore; Monensin; Residues; Screening; Immunoassay; Time-resolved fluorometry

Monoclonal antibody-based enzyme-linked immunosorbent assays for the detection of the organophosphorus insecticide isofenphos by Won Young Lee; Eun Kyung Lee; Yoo Jung Kim; Won Chul Park; Taeowan Chung; Yong Tae Lee (pp. 169-178).

In our previous study, polyclonal antibodies against the organophosphorus insecticide isofenphos were generated and enzyme-linked immunosorbent assays (ELISAs) for this pesticide were developed. In this study, isofenphos ELISAs with higher performance were developed by using a monoclonal antibody and a larger number of immunoreagents. Using the antibody and a coating antigen, an indirect competitive ELISA for isofenphos was developed, which showed an IC₅₀ value of 35ng/mL with a detection limit of 5.8ng/mL. A direct competitive ELISA using an enzyme tracer was also developed, which showed an IC₅₀ value of 26ng/mL with a detection limit of 4.8ng/mL. The antibodies in both assays showed negligible cross-reactivity with other OP pesticides. Recoveries of isofenphos from fortified rice and lettuce samples ranged 30–328 and 52–197%, respectively. The bias in the recovery values was rationalized by using the standard curves obtained in the matrix extract.

Keywords: Isofenphos; Organophosphorus insecticide; Immunoassay; Enzyme-linked immunosorbent assay

A morphological study of molecularly imprinted polymers using the scanning electron microscope by Gema Paniagua Gonz�lez; Pilar Fern�ndez Hernando; J.S. Durand Alegr�a (pp. 179-183).

Molecular imprinting is an emerging technique for producing polymers with applications in affinity-based separation, in biomimetic sensors, in catalysis, etc. This variety of uses relies upon the production of polymers with different affinities, specificities, sensitivities and loading capacities. Research into the development of molecular imprinted polymers (MIPs) with new or improved morphologies – which involves modification of the polymerisation process – is therefore underway. This paper reports a comparative study of non-covalent MIPs synthesised by “bulk�? polymerisation using digoxin as template. These were synthesised under different conditions, i.e., changing the functional monomers employed (methacrylic acid or 2-vinylpyridine), the porogens (acetonitrile or dichloromethane) used, and by altering the volume of the latter. The polymerisation process was allowed to proceed either under UV light or in a thermostat-controlled waterbath. The surface morphology (was determined by scanning electron microscopy) and the ability of the different polymers to selectively rebind the template was then evaluated.

Keywords: Molecularly imprinted polymers; Digoxin; Scanning electron microscope; Synthesis comparison

Estimation of association constants between oral malodor components and various native and derivatized cyclodextrins by Andrew W. Lantz; Michael A. Rodriguez; Sean M. Wetterer; Daniel W. Armstrong (pp. 184-190).

The association constants of 33 oral malodorous compounds and odor precursors (9 organic acids, 7 amine-containing bases, 11 organic neutral and aromatic compounds, and 6 amino acids) with native and derivatized cyclodextrins were measured using one or more of a variety of techniques including affinity capillary electrophoresis, nuclear magnetic resonance titrations, and head-space gas chromatography. With the exception of formic acid and urea, which had binding constants that were too small to measure, all analytes showed significant binding to at least one of the cyclodextrins studied. In most cases, the native cyclodextrins exhibited the most stable complexes with these analytes. However, with cationic analytes under acidic conditions, the negatively charged sulfated and carboxymethyl cyclodextrins had higher association constants. The six amino acid precursor molecules only bound significantly with the sulfated cyclodextrins. In addition, several analyte–cyclodextrin combinations were observed to form insoluble complexes, indicating that these cyclodextrins are particularly effective at extracting these compounds from aqueous solution.

Keywords: Halitosis; Odor; Oral hygiene; Binding; Cyclodextrins; Complexation

Product ion studies of diastereomeric benzo[ghi]fluoranthene-2′-deoxynucleoside adducts by electrospray ionization and quadrupole ion trap mass spectrometry by Linge Li; Hui-Fang Chang; Kenneth W. Olsen; Bongsup P. Cho; M. Paul Chiarelli (pp. 191-197).

The product ion formation characteristics of the protonated molecule ions generated from 10 different deoxynucleoside adducts of benzo[ghi]fluoranthene (B[ghi]F) have been studied using electrospray ionization (ESI) and quadrupole ion trap mass spectrometry to gain a better understanding of the fragmentation mechanisms that govern structure-specific fragmentation. The reaction of the syn- and anti-diastereomers of trans-3,4-dihydroxy-5,5a-tetrahydrobenzo[ghi]fluoranthene with DNA produce four deoxyguanosine, four deoxyadenosine, and two deoxycytidine adducts whose structures differ based on the cis/ trans arrangement of the hydroxyl groups and nucleic acids bound to B[ghi]F. Those adducts that have structures where the nucleic acid and 3′-hydroxyl group of B[ghi]F are cis with respect to each other undergo extensive water loss whereas those isomers where the nucleic acid and 3′-hydroxyl group are trans do not. These results are consistent with a mechanism of water loss initiated by a hydrogen-bonding interaction between the charge-bearing proton on a heterocyclic nitrogen atom on the nucleic acid and the 3′-hydroxyl oxygen on the PAH. The dG and dC adducts are observed to undergo more extensive water loss than the dA adducts. Molecular modeling indicates that the larger relative abundances of the product ions formed by water loss for the dG and dC relative to dA are due to stronger hydrogen-bonding interactions prior to fragmentation and the greater stability of the carbocations formed at the C3′ carbon after fragmentation.

Keywords: Electrospray ionization; Mass spectrometry; DNA adducts

Characterization of triterpenoidic saponin mixture in crude extracts from leaves of Acanthopanax senticosus Harms by saponin structural correlation and mass spectrometry by Mingquan Guo; Fengrui Song; Zhiqiang Liu; Shuying Liu (pp. 198-203).

Eighteen triterpenoidic saponins in crude extracts from leaves of Acanthopanax senticous Harms have been investigated by electrospray ionization multi-stage tandem mass spectrometry and high-resolution mass spectrometry. In ESI-MS spectra, predominant [M+Na]⁺ ions in the positive ion mode have been observed for molecular mass information. Meanwhile, specific structural correlations between these ions are firstly found. The 18 peaks (ions) can be classified into three groups (group D, E, and F with mass increase) with each group including six peaks. There is a mass difference of 132Da between group D and E for each corresponding peak in turn (for example peak 1 to peak 7), indicating one more pentose residue was attached to saponins in group E than those corresponding in group D. The mass difference of 146Da between group E and F implies one more deoxy-hexose attached to saponins in group F than those corresponding in group E. The structural correlations of the corresponding ions are confirmed by tandem mass spectrometry and high-resolution mass spectrometry. These structural features can not only facilitate the rapid characterization of the native known saponins in crude plant extracts, thus avoiding tedious derivation and separation of saponins, but also help find novel compounds of the same type in a specific medicinal plant. The structures of 14 known triterpenoidic saponins and four unknown saponins are thus determined or predicted. This methodology, with a combination of structural correlation of a complex mixture of homologs (which are difficult to separate) and mass spectrometry, has been established as a powerful and practical tool for the profiling of mixtures, especially of crude plant extracts and structural characterization of unknown compounds.

Keywords: Triterpenoidic saponin; Acanthopanax senticosus Harms; Electrospray tandem mass spectrometry; Structural correlation

Banned antibacterial growth promoters in animal feed: Collaborative trial on the liquid chromatography–tandem mass spectrometry method developed in the feedstuffs-radius project by Christof Van Poucke; Fr�d�ric Dumoulin; Shirish Yakkundi; Chen Situ; Chris T. Elliott; Ellen M. Grutters; Ron Verheijen; Robert Schilt; Sune Eriksson; Carlos Van Peteghem (pp. 204-210).

A chemical confirmation method for the identification and quantification of five banned antibacterial growth promoters (AGPs) in animal feed was developed and in-house validated as part of the European Feedstuffs-RADIUS project . To complete the validation process a collaborative trial was performed by eleven laboratories within the European Union (EU) using the developed method. Laboratories were supplied with six animal feed samples. None of the participants reported any false non-compliant results on these samples. Neither where there any false compliant results for four out of five compounds. These data proved the procedure to be robust and an excellent means of controlling misuse of the banned antibacterial growth promoters. During a small feed survey, a selection ( n=614) of animal feed samples were screened with a multi-antibiotic ELISA method that was developed in the same EU project and non-compliant samples were submitted to liquid chromatography-tandem mass spectrometry (LC–MS/MS) confirmation. The results from this confirmatory analysis indicated that the LC–MS/MS method will be a valuable tool in helping to determine the origin of the detected antibacterial compounds and that animals are still receiving tylosin in concentrations that are in the same range as the now banned AGP concentrations.

Keywords: Collaborative trial; Antibacterial growth promoters; LC–MS/MS; Feedstuffs survey; Cross-contamination; Medicated feed

A liquid chromatography – tandem mass spectrometry method for simultaneous analysis of acrylamide and the precursors, asparagine and reducing sugars in bread by Nikoline J. Nielsen; Kit Granby; Rikke V. Hedegaard; Leif H. Skibsted (pp. 211-220).

A LC–MS–MS method for simultaneous determination of acrylamide, asparagine, fructose, glucose and sucrose in bread was developed. The method is based on aqueous extraction by blending. After centrifugation the samples were cleaned up by solid phase extraction on C18 cartridges conditioned with 2mL of methanol and 2× 2mL of water and subsequently flushed with sample solution before the actual analytical sample fractions were collected. Analytes were separated on a Hypercarb column (100mm×2.1mm, 5μm) and detected by tandem MS with electrospray ionisation. Acrylamide and saccharides were ionised in positive mode. Asparagine in wheat bread was detectable at lower levels using negative ion mode. To compensate for matrix induced signal suppression D₃-acrylamide and¹⁵N₂-asparagine were used as internal standards for acrylamide and asparagine, respectively. Recoveries were in the range 93–112% for acrylamide spiked at 30, 250μgkg⁻¹ and 97–101% for asparagine spiked at 70, 140mgkg⁻¹. Sorbitol was used as internal standard for fructose and glucose. Samples were diluted to obtain acceptable recoveries in saccharide analyses. LODs were 13μgkg⁻¹ for acrylamide and 2mgkg⁻¹ for asparagine in wheat bread.

Keywords: Acrylamide; Asparagine; Fructose; Glucose; Sucrose; Analysis

Cellulose 3,5-dimethylphenylcarbamate immobilized on silica by Tong Zhang; Dung Nguyen; Pilar Franco; Tatsushi Murakami; Atsushi Ohnishi; Hidehiro Kurosawa (pp. 221-228).

Recently, we have reported the solvent versatility and enantiomeric resolution performance of an immobilized amylose derivative-based chiral stationary phase (CSP), CHIRALPAK^® IA. The second member in the same series of immobilized CSPs is CHIRALPAK^® IB. This new CSP is prepared by immobilizing the chiral selector (the 3,5-dimethylphenylcarbamate derivative of cellulose) onto a 5μm spherical porous silica. The aim of this work is to obtain an insight into the chromatographic performance in enantiomeric separation of this new CSP. In addition, we will explore and exploit its enantioselective ability with “non-standard�? solvents in the mobile phase. Fundamental information regarding the selection of mobile phases and additives for efficient method development is presented. The CSP stability under “non-standard�? mobile phase conditions is demonstrated.

Keywords: Enantiomeric separation; Chiral stationary phase; Immobilization; 3,5-Dimethylphenylcarbamate of cellulose; Analytical application; HPLC

Estimation of tegaserod in human plasma by high-performance liquid chromatography–tandem mass spectroscopy and its application to bioequivalence study by Sonu Sundd Singh; Harshvardhan Patel; Kuldeep Sharma (pp. 229-235).

A sensitive and novel HPLC–tandem mass spectrometric method has been developed for the estimation of tegaserod in human plasma using atorvastatin as internal standard. The methodology involved solid phase extraction (SPE) of the analyte from human plasma, using the Water's Oasis^® HLB 1cm³ (30mg) cartridges. The chromatographic separation was achieved within 5min on XTerra MS C18, 100mm×2.1mm i.d., 3.5μm analytical column with an isocratic mobile phase containing a mixture of acetonitrile and 0.2% formic acid in water (50:50, v/v) flowing through it at the rate of 0.3ml/min. Multiple reaction monitoring (MRM) transitions; m/ z 302.2, 173.2 and 559.0, 439.7 were measured in positive mode for tegaserod and internal standard, respectively. A detailed validation of the method was performed as per USFDA guidelines. The standard curves were linear in the range 0.2–20.0ng/ml with the mean correlation coefficient more than 0.99. The absolute recovery for tegaserod was more than 70%. The method was simple, sensitive, precise, accurate and suitable for routine bioequivalence and pharmaco-kinetic studies. The method was successfully applied to the bioequivalence study of tegaserod tablets in healthy, male human subjects.

Keywords: Tegaserod; Human plasma; Validation; Bioequivalence

Characterization of major and minor capsaicinoids and related compounds in chili pods ( Capsicum frutescens L.) by high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry by Ute Schweiggert; Reinhold Carle; Andreas Schieber (pp. 236-244).

Capsaicinoids were extracted from fresh chili pods ( Capsicum frutescens L.) and characterized by high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry. Among the 23 compounds detected, 3 major and 12 minor capsaicinoids belonging to the ‘capsaicin’, ‘dihydrocapsaicin’ and ‘ N-vanillyl- n-acylamide group’, respectively, were characterized by their specific fragmentation pattern in collision-induced dissociation experiments. Additionally, with the exception of ω-hydroxycapsaicin, several closely related compounds were tentatively identified as alkyl dehydrogenated and -hydroxylated derivatives, respectively, for the first time in Capsicum fruits.

Keywords: Chili; LC–MS; ⁿ; Capsaicinoids; Capsaicinoid derivatives

Development and validation of a fast high-performance liquid chromatography method for the determination of microencapsulated pyrethroid pesticides by Isabel Patricia Rivas; M. Esther Gil-Alegre; Ana Isabel Torres-Su�rez (pp. 245-251).

The use of microencapsulated pesticides in urban and rural pest control obliges to develop valid analytical methods for both free and microencapsulated pesticide. An analytical procedure for the pesticide quantification by reversed phase-high-performance liquid chromatography (RP-HPLC) based on pesticide extraction from the microcapsules by dissolution of the wall with dimethylacetamide and the quantification of pesticide in the presence of the polymer is proposed. The shell of the Commercial Insecticide Microcapsules is mainly made of polyurea or polyamide. For this reason, cypermethrin loaded polyurea microcapsules are used as model. The proposed analytical procedure is proportional, accurate and precise, in the range from 0.2 to 1.2μg, using as solvent dimethylacetamide:acetonitrile (5:95). It has been successfully proved for the quantification of microencapsulated pesticide in vegetables.

Keywords: Pyrethroids; Microcapsules; Pesticides; High-performance liquid chromatography; Validation

Determination of finasteride in the tablet form by liquid chromatography and its analytical method validation by Hulya Demir; Aysen Cucu; Serap Sakarya (pp. 252-255).

A quantitative method for finasteride by liquid chromatography (LC) with UV detector, was validated for its new tablet form Dilaprost^®. Analysis was performed using Nova Pak C₁₈ column at 60°C. Detection was carried out at a wavelength of 210nm. The best separation for finasteride peak was achieved by isocratic elution with the mobile phase water/acetonitrile/tetrahydrofuran (80/10/10, v/v/v) and flow rate of 2mLmin⁻¹. The sample volume injected into liquid chromatography system was 15μL. Analytical method validation tests were performed.

Keywords: Finasteride; Dilaprost; ^�; Validation

Simplified method for the determination of N-nitrosamines in rubber vulcanizates by Joseph A. Incavo; Melvin A. Schafer (pp. 256-261).

A simplified method for the trace determination of N-nitrosamines in carbon black-loaded rubber compounds is described. The extraction of volatile nitrosamines is accomplished by thermal desorption rather than the traditional solvent extraction procedure. The analytes are trapped on Thermosorb/N sorbent and subsequently analyzed by gas chromatography with thermal energy analyzer detection (GC/TEA). Conditions that provide full extraction of nitrosamines from actual rubber compounds were determined to be 30min at 150°C in vessels dynamically purged with N₂. Method precision was found to be 10% for NDMA at 71ng/g and 7.3% for NMOR at 248ng/g. Recoveries for the seven common N-nitrosamines ranged from 94 to 117%. Limits of detection in the rubber matrix are 6.3–13ng/g. The technique is found to offer improved recovery of lower molecular weight nitrosamines and it is shown to be simpler and faster than previous techniques.

Keywords: Nitrosamines; Rubber; Vulcanizates; Desorption; TEA

Determination of dihydroxyacetone and glycerol in fermentation broth by pyrolytic methylation/gas chromatography by Wang Lili; Qian Jie; Hu Zhongce; Zheng Yuguo; Hu Wei (pp. 262-266).

A method to determine dihydroxyacetone (DHA) and glycerol in fermentation broth was developed on the basis of pyrolytic methylation–gas chromatography (GC) using a vertical microfurnace pyrolyzer. With the on-line pyrolytic methylation in the presence of an organic alkali, tetramethylammonium hydroxide ((CH₃)₄NOH, TMAH), DHA and glycerol were converted into their corresponding methyl ethers. Thus, fermentation broth samples containing DHA and glycerol could be well determined simultaneously by this pyrolytic methylation–GC without using any pretreatment procedures. Important factors such as reaction temperature, the amount of TMAH to DHA and glycerol were investigated in order to obtain the optimum methylation conditions. Thus, obtained results showed that 0.4μl 25% TMAH aqueous solution at 400°C enabled the highly sensitive determination of DHA and glycerol contained in 0.2μl aqueous samples. The achieved calibration curves exhibit good linearity with regression coefficients of 0.996 and 0.998 for DHA and gelycerol at the concentration range from 1 to 100g/l, respectively. The precision was quite high with the R.S.D. within 5.0% for DHA at 30g/l and glycerol at 15g/l concentration levels, and the limit of detection reached 0.016g/l. The potential of the proposed method was assessed by applying it to determination of both the analytes in fermentation broth during the bioconversion of glycerol to DHA by Acetobacteria sp. The results proved that this on-line pyrolytic methylation–GC technique was a rapid, convenient and highly sensitive method for monitoring the bioprocesses of DHA.

Keywords: Pyrolytic methylation; TMAH; GC; Dihydroxyacetone; Glycerol; Bioconversion

Fast quantitative determination of volatile constituents in fennel by headspace-gas chromatography by Mitja Križman; Dea Bari�?evi�?; Mirko Prošek (pp. 267-271).

A headspace-gas chromatography method for analyzing volatile constituents in fennel ( Foeniculum vulgare) fruits and leaves has been developed. The use of the full evaporation technique (FET) in combination with short chromatographic run times allows over 100 samples per day to be analyzed. Dependently on the sample type, little or virtually no sample preparation is needed. The method was validated for the major volatile constituents present in fennel fruits: α-pinene, α-phellandrene, limonene, fenchone, estragole and trans-anethole. The method has proven to be linear from sub-microgram levels to 1000μg for each analyte studied present in the sample. The limits of detection (LOD) and the limits of quantitation (LOQ) ranged from 0.07 to 0.2μg and from 0.2 to 0.5μg, respectively. Anisaldehyde, a degradation product of trans-anethole, was also included in the study. Due to its linearity, sensitivity and efficient separation the method use could be extended to other compounds present in fennel as well. Oxidation stability of trans-anethole during headspace sampling was also assumed.

Keywords: Headspace; Gas chromatography; Full evaporation technique; Fennel; Foeniculum vulgare; Essential oil

Stir bar sorptive extraction and thermal desorption-gas chromatography-mass spectrometry for trace analysis of benzophenone and its derivatives in water sample by Migaku Kawaguchi; Rie Ito; Naoyuki Endo; Norihiro Sakui; Noriya Okanouchi; Koichi Saito; Nobutake Sato; Takuya Shiozaki; Hiroyuki Nakazawa (pp. 272-277).

A simple and highly sensitive method called stir bar sorptive extraction (SBSE) and thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS), which is used for the determination of trace amounts of benzophenone (BP) and its derivatives, 2-hydroxy-4-methoxybenzophenone (BP-3) and 2-hydroxy-4-methoxy-4′-methylbenzophenone (BP-10), in river water samples, is described. A stir bar coated with polydimethylsiloxane (PDMS) is added to a 10ml water sample and stirring is carried out for 120min at room temperature (25°C) in a vial. Then, the PDMS stir bar is subjected to TD-GC-MS. The detection limit is 0.5–1pgml⁻¹ for BPs. The method shows good linearity and the correlation coefficients are higher than 0.997 for all the analytes. The average recoveries of the BPs are equal to or higher than 98.5% (R.S.D.: 1.5–5.1%). This simple, accurate, sensitive and selective analytical method may be used in the determination of trace amounts of BPs in river water samples.

Keywords: Benzophenone; Water sample; Stir bar sorptive extraction (SBSE); Thermal desorption (TD); Gas chromatography-mass spectrometry (GC-MS)

Pure and modified water assisted by auxiliary energies: An environmental friendly extractant for sample preparation by S. Morales-Mu�oz; J.L. Luque-Garc�a; M.D. Luque de Castro (pp. 278-286).

The growing trend both to avoid the use of organic solvents and reduce the time needed to extract pollutants from environmental solid samples has led to the use of water assisted by auxiliary energies for leaching. The most common of the auxiliary energies used are high pressure–high temperature, microwaves and ultrasounds. One of the most interesting aspects of the use of water in combination with auxiliary energies is the possibility of coupling extraction with other steps of the analytical process, thus enabling partial or total automation of the analytical process, so it is expedited. The addition of reagents (such as surfactants, acids, etc.) to water enlarges its field of application and provides an additional way of shortening the leaching time; thus allowing the establishment of environmental friendly methods. A review about the potential of water as extractant and its main applications so far is here presented.

Keywords: Water; Auxiliary energies; Sample preparation

Critical factors and pitfalls affecting the extraction of acrylamide from foods: An optimisation study by Erik V. Petersson; Johan Ros�n; Charlotta Turner; Rolf Danielsson; Karl-Erik Hellen�s (pp. 287-295).

A stepwise study of common factors for the extraction of acrylamide (AA) from relevant food matrices was performed. The investigated extraction factors were sample particle size (fine or coarse), defatting (yes or no), extraction solvent (water or water/methanol), homogenisation by Ultra Turrax (yes or no), extraction temperature (25 or 60°C) and extraction time (5min to 17h). An optimised method comprised the use of fine particles (<1000μm), water as the extraction solvent and shaking of the sample for 45min at 25°C. This extraction method was suitable for all tested matrices (coffee, crispbread, mashed potatoes, milk chocolate and potato crisps). The analytical results (from LC-MS/MS analysis after SPE clean-up) correlated well with those obtained by the original, more labour-intensive, extraction procedure and there was excellent agreement with the assigned AA levels of several proficiency test samples analysed for evaluation. Defatting and additional homogenisation by Ultra Turrax did not increase the AA yield when other factors were set to appropriate levels. In general, the study indicates that incomplete extraction is the most likely cause of erroneous results. This might occur when the food is not sufficiently macerated, when water/methanol is used as the extraction solvent, and when using a short extraction time or low extraction temperature, especially when these conditions are combined. Formation of AA during the extraction procedure is another possible error source, though it was not seen under any of the experimental conditions employed when a fructose-enriched blank potato tissue was extracted.

Keywords: Acrylamide; Foods; Analysis; LC-MS/MS; Extraction; Optimisation; Method optimisation

A comparative study of acid-extractable and total digestion methods for the determination of inorganic elements in peat material by inductively coupled plasma-optical emission spectrometry by Charun Yafa; John G. Farmer (pp. 296-303).

In the absence of a standard wet preparation method for the determination of inorganic elements in peat, four acid digestion methods (nitric acid (HNO₃), HNO₃/hydrochloric acid (HCl), aqua regia and HNO₃/hydrofluoric acid (HF)) were compared using a Canadian fen peat (OGS 1878 P-6), previously proposed as a reference material, and inductively coupled plasma-optical emission spectrometry (ICP-OES) as the instrumental analytical technique. Two microwave-assisted methods, HNO₃ and HNO₃/HF, representing ‘acid-extractable’ and total digestion, respectively, were then selected for optimisation and application to a newly developed ombrotrophic peat reference material (NIMT/UOE/FM/001) and to the individual sections of a 43cm peat core, also from Flanders Moss, Scotland, for a range of elements, including Al, Co, Cr, Cu, Fe, Mn, P, Pb, S, Ti, V and Zn. While the results suggested the general efficacy of HNO₃ in investigations of the greatly elevated levels of trace elements, such as Cu, Pb and Zn, resulting from the severe anthropogenic contamination of the environment during the industrial era, the need for addition of HF for the determination of major lithogenic elements, such as Al and Ti, present in aluminosilicates and other resistant minerals, and some trace elements (Co, Cr and V) was clearly demonstrated. The inclusion of HF in a total digestion method, such as HNO₃/HF, is, therefore, necessary when normalisation of trace element concentrations to those of a conservative lithogenic reference element, such as Ti, is performed for the purpose of determining elemental enrichment factors. For elements other than Hg, the dry ashing of peat samples at 450°C prior to acid digestion is recommended for the destruction of the predominantly organic matrix, especially relevant where inductively coupled plasma-mass spectrometry (e.g. quadrupole inductively coupled plasma-mass spectrometry (ICP-MS)) is to be used in the determination of the much lower concentrations of trace elements prevalent in pre-industrial and ancient times.

Keywords: Acid digestion; Peat; ICP-OES; Elements

Optimization of a microwave-assisted extraction large-volume injection and gas chromatography–ion trap mass spectrometry procedure for the determination of polybrominated diphenyl ethers, polybrominated biphenyls and polychlorinated naphthalenes in sediments by V. Yus�; O. Pardo; A. Pastor; M. de la Guardia (pp. 304-313).

A sensitive and rapid method for the determination of polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs) and polychlorinated naphthalenes (PCNs) in sediment samples is proposed. The method involving microwave-assisted extraction (MAE) and large-volume injection (LVI) gas chromatography (GC)–ion trap mass spectrometry (ITMS), and the experimental conditions were optimized using the statistical design of experiments (DOE).A Plackett–Burman (P–B) design was chosen to estimate the influence of five factors, such as resonance excitation voltage (EV), isolation time (IT), excitation time (ET), ion source temperature (IST) and electron energy (EE) on the analytical response in the ITMS determination.In order to increase the analytical response, 70μL of the final extract were injected into the GC–tandem mass spectrometry (MS–MS) using a programmable temperature vaporizer (PTV). The factor settings involving injection temperature, vaporization temperature, vaporization time and flow during the evaporation step were previously optimized using a central composite design (CCD).The MAE was carried out using the hexane–acetone (1:1, v/v) mixture and the extraction conditions were optimized with a CCD. The highest response was obtained with a volume of 48mL, a temperature of 152°C and an extraction time of 24min. The optimized method gives recoveries between 75 and 95% with relative standard deviations (R.S.D.) that ranged from 4 to 13%. The limit of detection (LOD) ranged between 4 and 20pgg⁻¹ dry weight (dw) when 5g of sediment were analyzed. The MAE method was applied to the analyses of polyhalogenated compounds in sediments collected in the harbour of Valencia (Spain).The proposed method may serve as an alternative for GC–negative chemical ionization (NCI)–MS and can be used in government testing programmes.

Keywords: Microwave-assisted extraction; Polybrominated diphenyl ethers; Polybrominated biphenyls; Polychlorinated naphthalenes; Design of experiments; Large-volume injection; Sediments

Separation of polybrominated diphenyl ethers, polychlorinated biphenyls, polychlorinated dibenzo- p-dioxins and dibenzo-furans in environmental samples using silica gel and florisil fractionation chromatography by Hanxia Liu; Qinghua Zhang; Zongwei Cai; An Li; Yawei Wang; Guibin Jiang (pp. 314-320).

A comprehensive procedure was established for the fractionation of solvent-extracted environmental samples into three fractions containing polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzo- p-dioxins and dibenzo-furans (PCDD/Fs), respectively. The procedure includes multi-layer silica gel chromatography to separate PBDEs from PCBs and PCDD/Fs, and subsequent separation of PCBs from PCDD/Fs using a florisil column. The numbers of congeners involved were 16, 19, and 17, for PBDEs, PCBs, and PCDD/Fs, respectively. The separation of the three chemical groups overcomes the potential mutual interferences, which are difficult to avoid even by the use of high resolution mass spectrometer (HRMS). In addition, this procedure efficiently eliminates most interfering substances from sample matrices for the subsequent instrumental analyses. The method was validated using mixed chemical standards, and applied for the analysis of environmental samples including sediment, sewage sludge and fish tissue. All the recoveries are within the acceptable ranges specified in the USEPA standard methods.

Keywords: PBDEs; PCBs; PCDD/Fs; Silica gel chromatography; Florisil; HRGC/HRMS

Nafion membrane-supported ionic liquid–solid phase microextraction for analyzing ultra trace PAHs in water samples by Yu-Nung Hsieh; Ping-Chih Huang; I-Wen Sun; Thou-Jen Whang; Ching-Yun Hsu; Hong-Hsin Huang; Chun-Hsiung Kuei (pp. 321-328).

A Nafion membrane-supported ionic liquid (IL)–solid phase microextraction (SPME) coupled to gas chromatography (GC)–mass spectrometry (MS) technique for the simultaneous sampling and determination of ultra trace polycyclic aromatic hydrocarbons (PAHs) in aqueous samples has been developed. The hybrid IL–SPME fiber was precoated with Nafion membrane prior to IL film to enhance the amount and stability of IL film absorbed on the fiber. The analytes were extracted by the head space mode, and then directly desorbed in the injection port of GC–MS. The hybrid IL–SPME fiber was newly coated for each extraction, and the coating and washing out processes accomplished in a few minutes. The extraction efficiency between the IL–SPME fibers coated with and without Nafion-supported membrane for the five tested PAHs was compared. The results show that fibers coated with Nafion could extract two to three times more amount of analytes (based on peak area) than those without it. The extraction efficiency of three ILs (1-methyl-3-octylimidazolium trifluoromethanesulfonate: [C₈mim][TfO], 1-benzyl-3-methylimidazolium trifluoromethanesulfonate: [Bemim][TfO] and 1-methyl-3-phenylpropylimidazolium trifluoromethanesulfonate: [Phpromim][TfO]) was evaluated; [C₈mim][TfO] has the greatest extraction efficiency. The SPME experimental conditions, the extraction temperature, time and the salt effect were studied and optimized. Two natural water samples were used to evaluate this proposed method. Naphthalene, fluorene and anthracene were detected in sample 1 (29.7–70.0pgmL⁻¹), whereas fluoranthene and pyrene were below the detection limit (5pgmL⁻¹). For sample 2, all of the five PAHs were below the detection limit (4–5pgmL⁻¹). However, good spiking recoveries (80–110%) and repeatability (R.S.D.<12%) were achieved. The results suggest that Nafion-supported IL–SPME has the potential for determining the ultra trace PAHs in aqueous samples.

Keywords: Ionic liquid; Nafion membrane; Solid phase microextraction; Polycyclic aromatic hydrocarbons; GC–MS; Natural water samples

Extraction of testosterone and epitestosterone in human urine using 2-propanol–salt–H₂O system by Hailing Liu; Chiyang He; Dawei Wen; Huwei Liu; Feng Liu; Kean Li (pp. 329-336).

Based on the 2-propanol–salt–H₂O system, a new and simple pretreatment method was developed for the analysis of testosterone and epitestosterone in human urine coupled with high-performance liquid chromatography (HPLC). The influence factors on partition behaviors of the steroids were studied including the type and amount of salts, the volume of 2-propanol, the concentration of the analytes, and temperature. When K₃PO₄, K₂HPO₄, K₂CO₃ and KOH were chosen as phase separation salts, the enrichment factors were 12, 10, 12 and 13, respectively, and the extraction efficiencies for testosterone and epitestosterone were all 80–90%. In the optimal system of 2-propanol–K₃PO₄–H₂O, the recoveries of the spiked standards for the analytes were all 92–102% with relative standard deviation of 2.3–7.2%. Combined with a HPLC method, this extraction technique has been successfully applied to the analysis of testosterone and epitestosterone in human urine with the detection limits of 1ng/ml and the linear ranges of 10–500ng/ml for both compounds. Compared with conventional liquid–liquid extraction or solid-phase extraction, this novel method is much simpler and more environmentally friendly due to the direct injection of the upper phase into HPLC system, no use of harmful organic solvent, and low consumption of extractant.

Keywords: Extraction; Testosterone; Epitestosterone; Aqueous two-phase system; 2-Propanol; High-performance liquid chromatography

Study of trace metal partitioning between soil–EDTA extracts and Chelex-100 resin by Nastaran Manouchehri; Alain Bermond (pp. 337-343).

The partitioning of Cu, Cd and Pb in EDTA leachates from a variety of soils, to Chelex-100 resin was investigated. A series of experiments was conducted to optimise method for the trace element sorption on Chelex-100 in 13 unpolluted soils from Burgundy, France. The extraction efficiency of Chelex-100 varied depending on soil carbonate contents. The largest percentage of trace metals was transferred to the resin in non-calcareous samples, while the resin was used in its Ca form. This technique was able to trap up to 98% of Cu, 72% of Cd and 28% of Pb in non-calcareous soil leachates. The fraction of metal transferred to the Chelex-100 in calcareous soil extracts was 40% less than those in non-calcareous ones.Besides, a kinetic procedure was developed to study the kinetic of cation exchange from soil–EDTA leachates onto solid-phase resin. The soil calcium content was found to be a controlling factor in the Cu sorption on the Ca–Chelex. Two different kinetic behaviours were observed in calcareous and non-calcareous soils. The dissociation rate of Cu in non-calcareous soil extracts was 10 times higher than that in calcareous ones. Application of kinetic model indicated the presence of two components associated to Cu in non-calcareous samples. This was discussed in terms of metal sorption mechanism from soil solution onto chelating resin.

Keywords: Soil trace metal; EDTA; Resin Chelex-100; Kinetics

Trace metal distribution in the Arosa estuary (N.W. Spain): The application of a recently developed sequential extraction procedure for metal partitioning by Rebeca Santamaria-Fern�ndez; Mark R. Cave; Steve J. Hill (pp. 344-352).

A study of the trace metal distribution in sediment samples from the Galician coast (Spain) has been performed. A multielement extraction method optimised via experimental design has been employed. The method uses centrifugation to pass the extractant solution at varying pH, through the sediment sample. The sequential leaches were collected and analysed by ICP-AES. Chemometric approaches were utilised to identify the composition of the physico-chemical components in order to characterise the sample. The samples collected at different sites could be classified according to their differences in metal bio-availability and important information regarding element distribution within the physico-chemical components is given. The method has proved to be a quick and reliable way to evaluate sediment samples for environmental geochemistry analysis. In addition, this approach has potential as fast screening method for the bio-availability of metals in the environment.

Keywords: Sequential extraction; Metal partitioning; Chemometrics; Estuary; Sediments; ICP-AES

Content uniformity and tablet hardness testing of intact pharmaceutical tablets by near infrared spectroscopy by Marcelo Blanco; Manel Alcal� (pp. 353-359).

The use of process analytical technologies by the pharmaceutical industry is a response to its growing need for improved productivity in order to face the increasing competition in this field. In this work, we explored the use of near infrared spectroscopy (NIRS) for the determination of physical (tablet hardness) and chemical parameters (active principle and content uniformity) in intact individual pharmaceutical tablets. Quantization was done by using a Partial Least Squares 1 (PLS1) calibration model constructed from laboratory calibration samples that were prepared by mixing the active principle and excipients, and pressing the mixture into tablets. The compaction pressure to be applied to the powder was previously determined by using another PLS1 model that allows calculating it from production tablets. The NIRS method used to quantify the active principle is simpler as the calibration set encompasses the variability sources present in production samples; also, it allows individual tablets to be analysed. The proposed method was validated in accordance with the International Conference on Harmonization (ICH) and The European Agency for the Evaluation of Medicinal Products (EMEA) guidelines, and found to be fit for its intended purpose.

Keywords: Content uniformity; Active principle ingredient; Tablet hardness; Rapid intact analysis; Process analytical technologies; Near infrared spectroscopy

Study of the aging and oxidation processes of vinegar samples from different origins during storage by near-infrared spectroscopy by Monica Casale; Mar�a-Jos� S�iz Abajo; Jos�-Mar�a Gonz�lez S�iz; Consuelo Pizarro; Michele Forina (pp. 360-366).

Near infrared spectroscopy combined with several chemometrical techniques has been used to control the aging process in vinegar and the changes produced during storage. Several considerations regarding NIR instrument changes, which can add noise to the determinations, were made and a strategy based on the correction of the spectra was used to eliminate the differences between spectra due to instrument variation, in particular to lamp change.Ninety-five different vinegars were measured using a near-infrared spectrometer. The spectrum of each vinegar sample was collected twice: the first time as soon as the bottle was opened and the vinegar had not undergone any oxidation process and the second measurement was taken after a certain period of time.Then, in order to quantify the discrimination between the two groups of spectra recorded in the two occasions and so to estimate the aging effect in the vinegar samples, Linear Discriminant Analysis was used as a classification method. To improve the results, bearing in mind that many of the measured variables could be useless and that the elimination of these wavelengths can help in interpretation, a feature selection technique was applied.For chemical interpretation of the retained wavelengths, the spectral zones correlated with the aging process were isolated and the species and compounds that can absorb in these NIR spectra bands were studied.

Keywords: NIR spectroscopy; Vinegar; Aging process; Spectra correction; Chemometrics

Determination of α-tocopherol in low-density polyethylene (LDPE) films by diffuse reflectance Fourier transform infrared (DRIFT-IR) spectroscopy compared to high performance liquid chromatography (HPLC) by A.Z. Graciano-Verdugo; E. Peralta; H. Gonz�lez-R�os; H. Soto-Valdez (pp. 367-372).

Quantification of α-tocopherol (α-T) from plastics is currently performed by high performance liquid chromatography (HPLC) with fluorescence detection, which requires solvent extraction of α-T from the films. This stage is very time consuming and has the risk of incomplete extraction or α-T degradation. In this work, a non-destructive analytical method for quantification of α-T in low-density polyethylene (LDPE) films by diffuse reflectance Fourier transform infrared (DRIFT-IR) spectroscopy was developed. Standard films were fabricated to give a final concentration of α-T from 0.13 to 1.74% as quantified by an HPLC method (C₁₈ columns with an isocratic elution with methanol:water (98:2) and fluorescence detection). HPLC analyses were performed by extracting the antioxidant from the films with tetrahydrofuran (THF) stabilized with BHT under controlled laboratory conditions (low-room temperature, light protection and cooled solvents). DRIFT-IR spectra were obtained for the standard films. The phenolic (C–OH) group vibration at 1209cm⁻¹ was used to quantify the α-T concentration. The LDPE band at 2019cm⁻¹ was used as internal standard. The ratio of the band heights (or areas) at 1209cm⁻¹/2019cm⁻¹ was used for quantification. Determination coefficients of 0.9997 and 0.9988 were obtained from the height and area ratio calibration curves (model equations), respectively. The predictive ability of the models were validated using the leave-one-out cross-validation approach based on the results from the solvent extraction and HPLC quantification technique performed under controlled laboratory conditions. This work is a response to a demand for analytical techniques that can be performed in a short time, are non-destructive, do not require solvents, and for which there is no need for controlled laboratory conditions.

Keywords: α-Tocopherol; Vitamin E; Antioxidants; DRIFT-IR; Low-density polyethylene films

Analytical characterisation of ancient mortars from the archaeological Roman city of Pollentia (Balearic Islands, Spain) by C. Genestar; C. Pons; A. M�s (pp. 373-379).

Analytical characterisation of historic mortars from the Roman city of Pollentia (Mallorca) has been carried out by means of thermal analysis (thermogravimetry (TG) and derivative thermogravimetry (DTG)), X-ray diffractometry (XRD) and Fourier transform infrared spectroscopy (FTIR).The aim of this research is to provide useful information about the construction mode of the mortars which served for lining purposes in duct drains, cisterns, swimming pools, flooring mortars and wall renderings. The reported results converge to reveal the hydraulic nature of the majority of the mortars used for several hundred years to cover the diverse needs of the inhabitants of Pollentia. A fair correlation between the chemical characteristics of the studied mortars and the results of ancient Roman mortars from other archaeological sites has been established.

Keywords: Ancient mortars; Roman mortars; Analytical characterisation; Thermal analysis; X-ray diffractometry; Fourier transform infrared spectroscopy

Automatic spectrophotometric procedure for the determination of tartaric acid in wine employing multicommutation flow analysis process by Elizabeth Nunes Fernandes; Boaventura F. Reis (pp. 380-386).

In the present work, an automatic flow procedure for the determination of tartaric acid in red wine without previous sample treatment is described. The flow system comprising three-way solenoid valves designed to implement the multicommutation flow analysis process. Under microcomputer control, the analytic procedure could be accomplished automatically without any intervention of the operator. The spectrophotomer method was based on the tartaric acid reaction with sodium vanadate. Intending to prove the effectiveness of the propose procedure, a set of red wine samples was analyzed. To permit accuracy assessment, wine samples were also analyzed using the OIV reference method. Applying the paired t-test between results obtained, no significant difference at 90% confidence level was observed. Other profitable features, such as a linear relationship between 0.50 and 10.0gl⁻¹ tartaric acid ( r=0.9998), a 2.1% coefficient of variation ( n=8), a sampling frequency of 28 determinations per hour, and a reagent consumption of 0.15mg sodium vanadate per determination were also achieved.

Keywords: Tartaric acid; Wine; Spectrophotometry; Multicommutation; Flow injection analysis; Automatic procedure

One-shot flow injection spectrophotometric simultaneous determination of copper, iron and zinc in patients’ sera with newly developed multi-compartment flow cell by Norio Teshima; Shingo Gotoh; Kazunori Ida; Tadao Sakai (pp. 387-392).

We propose here an affordable flow injection method for simultaneous spectrophotometric determination of copper, iron and zinc in patients’ sera. The use of a newly designed multi-compartment flow cell allowed the simultaneous determination of the three metals with a single injection (‘one-shot’) and a double beam spectrophotometer. The chemistry relied on the reactions of these metals with 2-(5-nitro-2-pyridylazo)-5-[ N-propyl- N-(3-sulfopropyl)amino]phenol (nitro-PAPS) to form corresponding colored complexes. At pH 3.8, only copper–nitro-PAPS complex was formed in the presence of pyrophosphate as a masking agent for iron, and then the copper and iron(II) complexes were formed in the presence of reductant (ascorbic acid) at the same pH, and finally all three metals reacted with nitro-PAPS at pH 8.6. The characteristics were introduced into the flow system to determine each metal selectively and sensitively. Under the optimum conditions, linear calibration curves for the three metals were obtained in the range of 0.01–1mgL⁻¹ with a sample throughput rate of 20h⁻¹. The limits of detection (3 σ) were 3.9μgL⁻¹ for copper, 4.1μgL⁻¹ for iron and 4.0μgL⁻¹ for zinc. The proposed method was applied to analysis of some patients’ sera.

Keywords: Multi-compartment flow cell; Spectrophotometry; Simultaneous determination; Copper; Iron; Zinc; Serum

Preferential color substances and optimized illuminations for computer screen photo-assisted classification by D. Filippini; I. Lundstr�m (pp. 393-398).

The computer screen photo-assisted technique (CSPT) is a practical method aimed at the evaluation of colorimetric assays using regular computer sets and web cameras as only instruments. The performance of CSPT, understood as its ability to distinguish different color substances, depends of the color of the evaluated substances and on the particular illuminating sequences used for the measurements. In this work, the systematic study of the CSPT performance for sets of 2 and 5 similar color substances is accomplished with the aid of a CSPT model. The result allows identifying specific substance transmittances most favorable with the classification capability of the technique, which is relevant for the design of assays customized for CSPT.The optimization of three colors short illuminating sequences (implying fast measurements) for specific sets of substances is demonstrated and compared with the performance for white illumination. The resulting average improvement in the performance, quantified as the Euclidean distance in a principal components space, for sets of 2 and 5 substances approximately doubles the result with white illumination, and presents performance peaks more than five times larger for critical substance sets.

Keywords: Home tests; Bioassays evaluation; Optimization; Point of care instrumentation; Computer screen illumination

Author Index (pp. 399-402).

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Analytica Chimica Acta (v.557, #1-2)