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Analytica Chimica Acta (v.550, #1-2)

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

Contents (pp. v-vi).

Calendar of forthcoming meetings (pp. n1-n2).

Filler Ad.: ACAEES (pp. ii).

Phase-transfer catalysis in analytical chemistry by Yiannis C. Fiamegos; Constantine D. Stalikas (pp. 1-12).

Phase-transfer catalysis (PTC) has been a well-established technique on the synthesis of organic chemicals for more than three decades. Its scope and underlying mechanistic features have been the subject of numerous studies and appear to be recognized and understood.This review is intended to approach the subject by focusing on the extraction–preconcentration–derivatization/reaction prior to analysis and to chronicle recent progress made. We present the salient aspects of PTC modes followed by a brief review of mechanistic considerations including reaction mechanisms, selectivity, rates and kinetics pointing out to the potency of PTC in analytical chemistry. Specific guidelines are given on how to optimize a PTC-based analysis with respect to catalyst, solvent, reaction conditions and more, based on reaction characteristics.Finally, using the PTC principles as a framework, selected real-life applications are provided, the capabilities and limitations of PTC are addressed for the purpose of direct analysis of organic analytes and certain advantages are highlighted.

Keywords: Phase-transfer catalysis; Micellar phase-transfer catalysis; Analytical applications

Bovine serum albumin-imprinted polyacrylamide gel beads prepared via inverse-phase seed suspension polymerization by Xingshou Pang; Guoxiang Cheng; Rensheng Li; Shulai Lu; Yihua Zhang (pp. 13-17).

Synthetic materials capable of specifically recognition proteins are important in bioseparation and biosensors. In this study, bovine serum albumin-imprinted polyacrylamide gel beads were synthesized via inverse-phase seed suspension polymerization, using high-density crosslinked gel beads as core, low-density crosslinked polyacrylamide gel as imprinting shell. The surface of gel bead had a large quantity of well-distributed macropores, which were suited to let the proteins pass in and out. The selectivity test showed that imprinting gel beads exhibited good recognition for template proteins, as compared to the control protein. We consider the formation of multiple hydrogen bonds and complementary shape between the imprinting cavities and the template proteins are the two factors that lead to the imprinting effect. The imprinting beads had quick adsorption rate and possessed improved regeneration property in comparison with those prepared directly via inverse-phase suspension polymerization.

Keywords: Polyacrylamide gel beads; Bovine serum albumin; Molecular imprinting; Recognition

Novel separation and preconcentration of trace amounts of copper(II) in water samples based on neocuproine modified magnetic microparticles by Parviz Ashtari; Kemin Wang; Xiaohai Yang; Shasheng Huang; Yadollah Yamini (pp. 18-23).

A novel, simple method based on magnetically assisted chemical separation (MACS) has been developed for analytical purposes. In this method, neocuproine modified magnetic microparticles was used for selective extraction and preconcentration of copper(II) ions from aqueous solutions. The advantages of this method include consumption of organic solvents almost eliminated and applications on unclear (containing suspended particles) samples without any preliminary filtration step. This method combines simplicity and selectivity of solvent extraction with easy separation of magnetic microparticles from solution with magnet. In addition, it can be considered as a simple method for determination of partition coefficient. The influence of different parameters, such as presence of extractant, amount of extractant loaded on the microparticles, reducing agent, pH, equilibrium time, ionic strength, type and least amount of stripping solution and limit of detection, were evaluated. Also, the effects of various cationic and anionic interferences on the percent recovery of copper were studied. Copper ions were extracted from solution at pH 6 and were stripped from microparticles with 0.5M HNO₃. Extraction efficiencies for solutions with volumes up to 100ml were >99%. Limit of detection was 1.5μg/l. The method was applied to the recovery and determination of copper in different water samples.

Keywords: Copper; Neocuproine; Magnetic microparticle; Separation

Selective adsorption, pre-concentration and matrix elimination for the determination of Pb(II), Cd(II), Hg(II) and Cr(III) using 1,5,9,13-tetrathiacyclohexadecane-3,11-diol anchored poly ( p-chloromethylstyrene-ethyleneglycoldimethacrylate) microbeads by Savaş Malcı; Cengiz Kavaklı; Ali Tuncel; Bekir Salih (pp. 24-32).

Poly( p-chloromethylstyrene-ethyleneglycoldimethacrylate) polymeric microbeads, poly( p-CMS-EGDMA), were synthesized and 1,5,9,13-tetrathiacyclohexadecane-3,11-diol (S4HD) was attached chemically onto the polymeric microbeads. Characterization of all microbeads was done by Fourier transform-infrared spectrometry (FT-IR) and elemental analyzer. The amount of attached 1,5,9,13-tetrathiacyclohexadecane-3,11-diol to the polymer was found to be 2.23mmolg⁻¹ polymers. The ligand attached microbeads, poly( p-CMS-EGDMA-S4HD), were used to examine the adsorption capacity of Pb(II), Cd(II), Hg(II) and Cr(II) ions for recovery, pre-concentration and the matrix elimination by changing the pH and the initial metal ion concentrations and also adsorption kinetics of the studied metal ions was determined. Pre-concentration factors for the studied toxic metal ions were found to be more than 500-fold and recovery was between 92 and 106%. In the drinking, lake, tap and sea-water samples from water lands, ultra-trace toxic metal ion concentrations were determined easily by using ligand modified microbeads after pre-concentration because of the high pre-concentration factor and easily matrix elimination using ligand modified microbeads. Reference sea-water material was used for the validation of the method and it was found that recovery, pre-concentration and the matrix elimination were performed perfectly. For the desorption of the toxic metal ions, 3M HCl containing 0.8M thiourea was used and desorption ratio was obtained more than 96%.

Keywords: Toxic metals; Pre-concentration; Matrix elimination; Recovery; Selective adsorption; Sorbent

Multi-pumping flow system for the determination, solid-phase extraction and speciation analysis of iron by Carmen Pons; Rafael Forteza; V�ctor Cerd� (pp. 33-39).

A multi-pumping flow system (MPFS) for the spectrophotometric determination, solid-phase extraction (SPE) and speciation analysis of iron at a wide range of concentrations is proposed. Chelating (iminodiacetic groups) disks have been used as solid phase. A solenoid valve allows the deviation of the flow towards the chelating disk to carry out SPE procedures. The possibility to combine solenoid micro-pumps with solenoid valves increases the versatility of MPFS. Ammonium thiocyanate has been chosen as chromogenic reagent for Fe(III). The determination of total iron is achieved by the on-line oxidation of iron(II) to iron(III) with a hydrogen peroxide stream.A mass calibration was run within the range 0.01–1.75μg. The detection limit (3 s_b/ S) was 0.01μg. The repeatability (R.S.D.) was estimated as 1.6% after 10-fold processing of 2ml of 0.5mgl⁻¹ Fe solution. When SPE was not required, two linear calibration graph within the ranges 0.05–10 and 0.2–15mgl⁻¹ for the determination of iron(III) and total iron, respectively, were obtained. The proposed procedure was validated by analysis of certified reference materials. The analytical features were compared with those obtained exploiting MSFIA.

Keywords: Multi-pumping flow system; Solid-phase extraction; Chelating disk; Preconcentration; Speciation

Determination of dioxopromethazine hydrochloride by capillary electrophoresis with electrochemiluminescence detection by Yunhui Li; Chunyan Wang; Jinying Sun; Yongchang Zhou; Tianyan You; Erkang Wang; YingSing Fung (pp. 40-46).

The paper presents a rapid method for the determination of dioxopromethazine hydrochloride (DPZ), an antihistamine drug, by the capillary electrophoresis with electrochemiluminescene detection (CE–ECL) using tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) reagent. This CE–ECL detection method has high sensitivity, good selectivity and reproducibility for DPZ analysis. Under the optimized conditions: separation capillary, 38cm length (25μm i.d.); sample injection, 10s at 8kV; separation voltage, 12.5kV; running buffer, 20mmolL⁻¹ sodium phosphate of pH 6.0; detection potential, 1.15V; 50mmolL⁻¹ of phosphate buffer (pH 7.14) containing 5mmolL⁻¹ of Ru(bpy)₃²⁺ in ECL detection cell, the detection limit of DPZ was 0.05μmolL⁻¹ (S/N=3). The linear range extended from 5 to 100μmolL⁻¹. The linear curve obtained was Y=181.62+9.28 X with a correlation coefficient of 0.9970. The relative standard deviations of the ECL intensity and the migration time for six continuous injections of 5μmolL⁻¹ DPZ were 3.7% and 0.92%, respectively. The CE–ECL method was applied to analyze DPZ in real samples including tablets, rat serum and human urine, and satisfactory results were obtained without interference from samples matrix. The CE–ECL technique was proved to be a potential method for the detection of DPZ in clinic analysis.

Keywords: Capillary electrophoresis; Electrochemiluminescence detection; Dioxopromethazine hydrochloride

Characterization of the low-oxidation-potential electrogenerated chemiluminescence of tris(2,2′-bipyridine)ruthenium(II) with tri-n-propylamine as coreactant by Yanbing Zu; Feng Li (pp. 47-52).

The electrogenerated chemiluminescence (ECL) of the Ru(bpy)₃²⁺ (bpy, 2,2′-bipyridine)/tri-n-propylamine (TPrA) system can be produced at an oxidation-potential well before the oxidation of Ru(bpy)₃²⁺. Here, we describe the unique features of the low-oxidation-potential (LOP) ECL. The LOP ECL exhibited strong dependence on solution pH with the maximum emission at pH∼7.7. Compared with the conventional ECL, the LOP ECL was much more significantly diminished at high pH (>10), probably due to the short lifetime of TPrA cation radical which is a crucial intermediate for the LOP emission. It was also found that the preceding deprotonation step played an important role in TPrA oxidation at neutral pH and would remarkably influence the emission intensity. As excess intermediate radicals were produced upon rapid TPrA oxidation, only 5mM TPrA was needed to achieve the maximum LOP ECL intensity in detecting trace Ru(bpy)₃²⁺ (<∼1μM) and the LOP ECL response to Ru(bpy)₃²⁺ concentration was linear. Compared with the conventional Ru(bpy)₃²⁺/TPrA ECL, the LOP ECL technique not only produces higher emission intensity at lower oxidation-potential, but also significantly reduces the amount of the coreactant.

Keywords: Electrogenerated chemiluminescence; Tris(2,2′-bipyridine)ruthenium(II); Tri-n-propylamine; Coreactant; Low-oxidation-potential emission

Solid-surface phosphorescence characterization of polycyclic aromatic hydrocarbons and selective determination of benzo( a)pyrene in water samples by A. Salinas-Castillo; J.F. Fern�ndez-S�nchez; A. Segura-Carretero; A. Fern�ndez-Guti�rrez (pp. 53-60).

This paper presents the phosphorescence characterization of polycyclic aromatic hydrocarbons (PAHs) on solid-surface for obtaining new flow-through phosphorescence optosensors for PAHs-based on-line, immobilized onto a non-ionic resin solid support coupled to a continuous flow system and the applications for the selective determination of benzo( a)pyrene (BaP). The phosphorescent characterization of 15 PAHs, described as major pollutants by the Environmental Protection Agency (EPA) (naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, chrysene, benzo( a)anthracene, benzo( k)fluoranthene, benzo( b)fluoranthene, benzo( a)pyrene, indeno(1,2,3- cd)pyrene, benzo( g, h, i)perylene and dibenzo( a, h)anthracene) has been carried out. The experimental variables (heavy atom, deoxygenation and organic solvent in samples) for obtaining different possibilities for developing mono and multi-parameter PAH sensors and the conditions for PAH screening have been carefully studied and the experimental conditions to determination of BaP in presence of other PAHs in water samples have been optimized.

Keywords: Phosphorescence optosensor; Flow-injection; Polycyclic aromatic hydrocarbons; Benzo(; a; )pyrene; Water

Assessing an imaging ammonium sensor using time correlated pixel-by-pixel calibration by Niklas Str�mberg; Stefan Hulth (pp. 61-68).

In this study, a ratiometric imaging ammonium sensor (optode) and a novel calibration technique for imaging optodes were developed, tested and thoroughly evaluated. The overall sensing scheme is based on ammonium coextraction together with a solvent sensitive dye in a hydrogel–ether emulsion. Quantification of ammonium during 10 days of experiments was made through an image ratio (excitation:emission/excitation:emission; 572nm:592nm/520nm:572nm ) coupled to the calibration technique i.e. time correlated pixel-by-pixel calibration (TCPC). Sensor performance was validated according to International Union of Pure and Applied Chemistry (IUPAC) recommendations for within-laboratory requirements of reproducibility, and compared with the more frequently used approach of image pixel calibration. Using the TCPC protocol; a limit of detection (LOD) of 1.2±0.2×10⁻⁶ M was calculated. The preliminary estimate of precision at 200×10⁻⁶ M, using relative standard deviation (R.S.D.) as a measure, was 5.2% over the 10-day period. The within-batch repeatability was 2.3% (R.S.D.) at 200×10⁻⁶M. A linear fit of the data compared the drift over time for the various calibration techniques. Without time correlation, the ratiometric pixel-by-pixel calibrated signal drifted significantly over time. The drift was more or less completely removed using the TCPC protocol. The image resolution, experimentally determined at the distance applied (3×10⁻¹m) by the 10–90% edge-response approach, was 210×10⁻⁶m. Imaging concentrations and diffusive transport of ammonium in soil during dissolution of a fertilizer stick was given as an example of a versatile sensor application.

Keywords: Imaging; Optode; Ammonium; Time correlated pixel-by-pixel calibration; TCPC; Optical sensor; Fluorescence ratio

Gold nanoparticle-enhanced surface plasmon resonance measurement with a highly sensitive quantification for human tissue inhibitor of metalloproteinases-2 by Ursula Pieper-F�rst; Walter F.M. St�cklein; Axel Warsinke (pp. 69-76).

Two different methods for the quantification of human tissue inhibitor of metalloproteinases-2 (TIMP-2) were developed using surface plasmon resonance (SPR) and gold nanoparticles for signal enhancement. The first method, a competitive assay, used TIMP-2 immobilized to the sensor surface and the inactive form of matrix metalloproteinase-2 (proMMP-2) (EC 3.4.24.24) adsorbed to gold nanoparticles. The sensor signals resulting from the interaction of MMP-2-gold nanoparticles with immobilized TIMP-2 were inversely proportional to the amounts of TIMP-2 of the sample. The measuring range for TIMP-2 was about 15–180pM. The second method, a one-step sandwich assay, used proMMP-2 immobilized to the sensor surface and an anti-TIMP-2 monoclonal antibody coupled to gold nanoparticles. The lower detection limit of this assay format was 0.5pM of TIMP-2. The binding signals were highly reproducible up to 100pM of the inhibitor. The improvements obtained in TIMP-2 quantification over already existing tests could contribute to a better understanding and diagnosis of diseases like cancer.

Keywords: Tissue inhibitor of metalloproteinases-2; Matrix metalloproteinase-2; Gold nanoparticle; Amplification; Surface plasmon resonance; Biacore 2000

Stochastic resonance is applied to quantitative analysis for weak chromatographic signal of glyburide in plasma by Wei Zhang; Bingren Xiang; Yanwei Wu; Erxin Shang (pp. 77-81).

Based on the theory of stochastic resonance, a new method carried on the quantitive analysis to weak chromatographic signal of glyburide in plasma, which was embedded in the noise background and the signal-to-noise ratio (SNR) of HPLC-UV is enhanced remarkably. This method enhances the quantification limit to 1ngml⁻¹, which is the same as HPLC-MS, and makes it possible to detect the weak signal accurately by HPLC-UV, which was not suitable before. The results showed good recovery and linear range from 1 to 50ngml⁻¹ of glyburide in plasma and the method can be used for quantitative analysis of glyburide.

Keywords: Stochastic resonance; Glyburide; Weak signal; High performance liquid chromatography

Chemometric analysis of groundwater quality data of alluvial aquifer of Gangetic plain, North India by Kunwar P. Singh; Amrita Malik; Vinod K. Singh; Dinesh Mohan; Sarita Sinha (pp. 82-91).

Water quality data set from the alluvial region in the Gangetic plain in northern India, which is known for high fluoride levels in soil and groundwater, has been analysed by chemometric techniques, such as principal component analysis (PCA), discriminant analysis (DA) and partial least squares (PLS) in order to investigate the compositional differences between surface and groundwater samples, spatial variations in groundwater composition and influence of natural and anthropogenic factors. Trilinear plots of major ions showed that the groundwater in this region is mainly of Na/K-bicarbonate type. PCA performed on complete data matrix yielded six significant PCs explaining 65% of the data variance. Although, PCA rendered considerable data reduction, it could not clearly group and distinguish the sample types (dug well, hand-pump and surface water). However, a visible differentiation between the water samples pertaining to two watersheds (Khar and Loni) was obtained. DA identified six discriminating variables between surface and groundwater and also between different types of samples (dug well, hand pump and surface water). Distinct grouping of the surface and groundwater samples was achieved using the PLS technique. It further showed that the groundwater samples are dominated by variables having origin both in natural and anthropogenic sources in the region, whereas, variables of industrial origin dominate the surface water samples. It also suggested that the groundwater sources are contaminated with various industrial contaminants in the region.

Keywords: Alluvial aquifer; Groundwater; Chemometric techniques; Principal component analysis; Discriminant analysis; Partial least squares

Exploring and modelling the responses of electrospray and atmospheric pressure chemical ionization techniques based on molecular descriptors by S. Caetano; T. Decaestecker; R. Put; M. Daszykowski; J. Van Bocxlaer; Y. Vander Heyden (pp. 92-106).

Mass spectroscopy with two different ionization techniques, electrospray ionization and atmospheric pressure chemical ionization, optimized for cocaine, was applied to study 170 molecules. For each of the molecules, 429 molecular descriptors were calculated. The aim of this work is, on one hand, to determine whether it is possible to identify which is the better ionization technique, electrospray ionization or atmospheric pressure chemical ionization, to analyse a given molecule, based on the calculated descriptors, and on the other hand to correlate the response of each of the techniques individually with these descriptors. For each molecule, the ratio between the corrected responses of electrospray ionization and atmospheric pressure chemical ionization was used as criterion to decide which ionization technique was the better for the analysis. The chemometrical methods used to explore and model the data were Principal Component Analysis, Projection Pursuit, Classification and Regression Trees, Partial Least Squares and Stepwise Multiple Linear Regression.The results obtained did not allow establishing, based on the calculated molecular descriptors, which is the better ionization technique to analyse a certain molecule for the studied data.

Keywords: Atmospheric pressure ionization methods; Principal Component Analysis; Projection Pursuit; Classification and Regression Trees; Partial Least Squares; Stepwise Multiple Linear Regression

Microchip micellar electrokinetic chromatography coupled with electrochemical detection for analysis of synthetic oestrogen mimicking compounds by Avril Collier; Joseph Wang; Dermot Diamond; Eithne Dempsey (pp. 107-115).

A miniaturised analytical system for separating and detecting a range of steroidal oestrogens, based on the coupling of a micromachined capillary electrophoresis chip with glassy-carbon electrode amperometric detector, is described. Factors influencing the on-chip separation utilising the technique micellar electrokinetic chromatography (MEKC) and detection processes are optimised. The addition of modifiers such as organic solvents and surfactants improve separation and resolution of these hydrophobic compounds. Using a borate running buffer (5mM, pH 11) with 20% methanol and SDS (20mM) and a separation voltage of 2000V, baseline resolution is observed for 16-keto-17β-oestradiol, oestriol, 11β-hydroxyoestradiol, oestrone, and β-oestradiol in 420s with limits of detection 16–84μM. The implications for on-site environmental analysis are discussed.

Keywords: Oestrogen mimics; Microchip; Capillary electrophoresis; Electrochemical detection

Simultaneous determination of pharmaceutically active compounds in wastewater samples by solid phase extraction and high-performance liquid chromatography with diode array and fluorescence detectors by J.L. Santos; I. Aparicio; E. Alonso; M. Callej�n (pp. 116-122).

In the present work, an analytical method for the simultaneous determination of five anti-inflammatory drugs (acetaminophen, diclofenac, ibuprofen, ketoprofen and naproxen), an antiepileptic drug (carbamazepine) and a nervous stimulant (caffeine) is proposed for the routine analysis of these pharmaceuticals in wastewater influents and effluents from WWTPs. The method involves pre-concentration and clean-up by solid phase extraction (SPE) using Oasis HLB extraction cartridges. Final analysis of the selected pharmaceutical compounds was carried out by high-performance liquid chromatography (HPLC) with diode array detector (DAD). Confirmation of the presence of the fluorescence compounds (ibuprofen and naproxen) was performed by on-line fluorescence detection. Recoveries were ranged from 71 to 103% with relative standard deviation below 15.1%. Limits of quantification were in the range 6.2–319.8 and 3.0–160.0ngml⁻¹ for influent and effluent wastewater samples, respectively. The described method was applied to the determination of the drugs in wastewater samples from four treatment plants in Seville.

Keywords: Pharmaceutical compound; Solid phase extraction; Wastewater; HPLC

Development and validation of HPLC methods for enantioseparation of mirtazapine enantiomers at analytical and semipreparative scale using polysaccharide chiral stationary phases by Zong-De Zhai; Yan-Ping Shi; Ting Wang (pp. 123-129).

Novel HPLC methods were developed for the analytical and semipreparative resolution of new antidepressant drug mirtazapine enantiomers. At analytical scale, the separation of the mirtazapine enantiomers was investigated using both cellulose and amylose tris(3,5-dimethylphenylcarbamate) (CDMPC and ADMPC) chiral stationary phases under normal-phases and polar organic modes. Good baseline enantioseparation was achieved using cellulose tris(3,5-dimethylphenylcarbamate) chiral stationary phases under both normal-phases and polar organic modes. Furthermore, the elution order of mirtazapine enantiomic pairs was found reversed by changing the stationary phase from the amylose-based ADMPC–CSPs to its cellulose-based counterpart, CDMPC–CSPs. The validation of the analytical methods including linearity, limit of detection (LOD), limit of quantification (LOQ), recovery and precision, together with the semipreparative resolution of mirtazapine racemate were carried out using cellulose tris(3,5-dimethylphenylcarbamate) chiral stationary phases and methanol as mobile phase without any basic additives under polar organic mode. At analytical scale, the elution times of both enantiomers were less than 6min at normal temperature and 1.0ml/min, with the separation factor ( α) 1.99 and the resolution factor (Rs) 3.56. Then, the analytical methods were scaled up to semipreparative loading to obtain small quantities of both mirtazapine enantiomers. At semipreparative scale, about 16mg/h enantiomers could be isolated and elution times of both enantiomers were less than 10min at 2.0ml/min. To increase the throughput, the technique of boxcar injections was used. One enantiomer ((−)-( R)-mirtazapine) was isolated with purity of >99.9% e.e. and >98.0% yield and another ((+)-( S)-mirtazapine) was isolated with purity of >97.0% e.e. and >99.0% yield. In addition, optical rotation and circular dichroism (CD) spectroscopy of both mirtazapine enantiomers isolated were also investigated.

Keywords: Enantioseparation; Polysaccharide carbamate phase; Semipreparative HPLC; Optical rotation; Circular dichroism; Mirtazapine

Behaviour of nucleotides and oligonucleotides in potentiometric HPLC detection by Y. Bao; J. Everaert; M. Pietraszkiewicz; O. Pietraszkiewicz; H. Bohets; H.J. Geise; B.X. Peng; L.J. Nagels (pp. 130-136).

Potentiometric HPLC detection was studied of mononucleotides (UMP, AMP, UDP, ADP, CTP, UTP, GTP, ATP) and oligonucleotides (a synthetic mixture d(T)_12–18 5′OH, a mixed 21-mer, 33-mer, and 60-mer). Coated-wire electrodes were used. The coatings were of the liquid membrane type containing PVC, DOS and synthetic macrocyclic amine- and podand ureum receptors. Electrodes based on these receptors gave very sensitive responses to triphosphate nucleotides and to oligonucleotides. The molar response of the oligonucleotides was related to their molar mass. The HPLC system consisted of a reversed phase column eluted with a phosphate buffer, triethylammoniumacetate (TEAA), and an acetonitrile gradient. The sensitive potentiometric response of these highly charged ions is discussed.

Keywords: Nucleotides; Oligonucleotides; HPLC; Potentiometry; Sensor

Characterization of zirconized silica supports for HPLC by Anizio M. Faria; Daniel R. Magalh�es; Kenneth E. Collins; Carol H. Collins (pp. 137-143).

The preparation and characterization of zirconized silica has been investigated. The material was prepared via the reaction of silica with zirconium tetrabutoxide, optimized by a central composite design and response surface methodology. The new material was characterized by nitrogen adsorption-desorption investigations (BET/BJH) showing specific surface areas adequate for use as a chromatographic support. DRUVS, FTIR, XPS, XAS, XRF and SEM methods also were used to characterize the new material. It was shown that silica networks were not significantly modified with the introduction of zirconium. Surface analyses show that there is appreciable element enrichment at the surface, while significant changes in binding energies of Zr 3d, Si 2p, and O 1s have been detected. The above observations indicate that SiOZr bonds were formed, with zirconium grafted onto the silica surface, yielding a support suitable for HPLC.

Keywords: Chromatographic support; Zirconized silica; XAS; XPS

Determination of Ga, Ge, As, Se and Sb in fly ash samples by ultrasonic slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry by Jiun-Long Ni; Chung-Chang Liu; Shiuh-Jen Jiang (pp. 144-150).

Ultrasonic slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry (USS-ETV-ICP-MS) has been applied to determine Ga, Ge, As, Se and Sb in fly ash samples. The influences of instrument operating conditions and slurry preparation on the ion signals were reported. Pd and ascorbic acid were used as the mixed modifiers to enhance the ion signals. This method has been applied to determine Ga, Ge, As, Se and Sb in NIST SRM 1633a and 1633b coal fly ash reference materials and a fly ash sample collected locally. Since the sensitivities of the elements studied in slurry solution and aqueous solution were different slightly, analyte addition technique was used for the determination of Ga, Ge, As, Se and Sb in these samples. The As and Se analysis results of the reference materials agreed with the certified values. The results for which no certified value was available were also found to be in good agreement between the ETV-ICP-MS results and the reference values. The reference value was obtained by digesting the samples and analyzing the digested sample solutions by pneumatic nebulization Dynamic Reaction Cell™ (DRC) ICP-MS. The method detection limits estimated from analyte addition curves were about 0.23, 0.13, 0.17, 0.25 and 0.11μgg⁻¹ for Ga, Ge, As, Se and Sb, respectively, in original fly ash samples.

Keywords: Inductively coupled plasma mass spectrometry; Ultrasonic slurry sampling; Electrothermal vaporization; Fly ash; Semiconductor elements

Simultaneous determination of total arsenic and total selenium in Chinese medicinal herbs by hydride generation atomic fluorescence spectrometry in tartaric acid medium by Zhanfeng Liu; Hanwen Sun; Shigang Shen; Liqing Li; Hongmei Shi (pp. 151-155).

By HG-AFS, a new method was proposed for simultaneous determination of total arsenic and total selenium existed in the Chinese medicinal herbs in tartaric acid medium. The effects of analytical conditions and coexisting ions on the fluorescence signal intensity of analytes were investigated. The proposed method was provided with linear response ranges above 22μgl⁻¹ for As and 44μgl⁻¹ for Se, and the detection limits of 0.13 and 0.12μgl⁻¹ were obtained for As and Se respectively. The recoveries of 93.8–96.1% for As and 95.3–99.1% for Se, and the precision of 1.2–3.8% and 2.4–5.3% (R.S.D., n=8) respectively, were obtained via simultaneous determined four samples of Chinese medicinal herbs and three certified botanic reference materials successfully. The proposed method has the advantages of simple operation, high sensitivity and high efficiency.

Keywords: Simultaneous determination; Arsenic; Selenium; Chinese medicinal herbs; Atomic fluorescence spectrometry

Binary modifiers for the determination of zinc in pure copper and nickel-based alloy by longitudinal Zeeman electrothermal atomic absorption spectrometry by Shi-Yang Chen; Chia-Ni Chang; Chun-Lien Li; Suh-Jen Jane Tsai (pp. 156-163).

The determination of zinc in pure copper and nickel-based alloy was successfully accomplished with a longitudinal Zeeman-effect correction and end-capped transversely heated graphite atomizer. Since aqua regia (an acid mixture of nitric acid and hydrochloric acid, 1:3, v/v) was used as the dissolving reagent, volatile ZnCl₂ was formed. Consequently, less Zn was found in the sample. EDTA could improve the atomic absorption profiles. Binary modifiers, EDTA+Pd(NO₃)₂ and EDTA+Mg(NO₃)₂, were effective for eliminating the chloride interference and the spectral interference from Cu I 213.853nm. The experimental results obtained with and without the modifiers were compared. Increase of 200�C in the pyrolysis temperature resulted from the addition of binary modifiers for both pure copper and nickel-based alloys. For pure copper, the atomization temperature increased from 1400 to 1600�C whereas the atomization temperature increased from 1100 to 1600�C for nickel-based alloys. The analytical performance of the proposed method was evaluated. Zinc contents in the pure copper and nickel-based alloy standards determined with both binary modifiers agreed closely with the certified values. The recovery ranged from 93�2 to 104�6% at 95% confidence level. The detection limits obtained by the binary modifiers of EDTA+Pd(NO₃)₂ and EDTA+Mg(NO₃)₂ were 0.77 and 0.31pg, respectively.

Keywords: Electrothermal atomic absorption spectrometry; Zinc; Pure copper; Nickel-based alloy; EDTA; Palladium; Magnesium

Spectroscopic investigation of a ‘ Virgin of Sorrows’ canvas painting: A multi-method approach by M. Ortega-Avil�s; P. Vandenabeele; D. Tenorio; G. Murillo; M. Jim�nez-Reyes; N. Guti�rrez (pp. 164-172).

The investigation of unmatched ancient objects is an attentive and arduous activity to conservation scientists. An important aspect of art analysis is the question on sampling and avoiding damage on the artefact during the study. A possible way to maximize the information that is extracted from the historical object is using several sensitive micro-analytical techniques on the same micro samples. As an illustration of this multi-method approach, in this work, a canvas painting ‘ Virgin of Sorrows’ was studied and its materials were analysed in order to roughly date and to authenticate this object of art. Proton induced X-ray emission (PIXE), neutron activation analysis (NAA), optical microscopy, scanning electron microscopy (SEM), micro-Raman spectroscopy (MRS) and Fourier transform infrared spectroscopy (FT-IR) were used, obtaining successful results. These methods allowed identifying the different inorganic pigments (iron oxide, carbon black, white lead, Prussian blue) as well as indigo. Optical microscopy and SEM revealed the layered structure of the samples, while FT-IR enabled to determine the nature of the varnish used (shellac). By using these complementary techniques, it was possible to identify the materials in the painting, which are indicative for the period of manufacturing the artwork.

Keywords: Art analysis; Pigments; Oil paintings; Falsification; Proton induced X-ray emission (PIXE); Scanning electron microscopy (SEM); Micro-Raman spectroscopy (MRS); Neutron activation analysis (NAA); Fourier transform infrared spectroscopy (FT-IR)

Novel fluorescent asparaginyl- N-acetyl-d-glucosamines (Asn-GlcNAc) for the resolution of oligosaccharides in glycopeptides, based on enzyme transglycosylation reaction by Jun Zhe Min; Toshimasa Toyo’oka; Hiroki Kawanishi; Takeshi Fukushima; Masaru Kato (pp. 173-181).

Several fluorescent asparaginyl- N-acetyl-d-glucosamines (Asn-GlcNAcs), i.e., DBD-Asn-GlcNAc, NBD-Asn-GlcNAc, NDA-Asn-GlcNAc, PS-Asn-GlcNAc, FITC-Asn-GlcNAc, DMEQ-Asn-GlcNAc and DBD-PZ-Boc-Asn-GlcNAc, were synthesized as the acceptors for the resolution of oligosaccharides in glycopeptides. The resolution of oligosaccharides is based on the transglycosylation reaction with end-β- N-acetylglucosaminidase (Endo-M), isolated from Mucor hiemalis. The synthesis of each fluorescent acceptor was carried out in a one-pot reaction of Asn-GlcNAc and the corresponding fluorescent tagging reagent. The transglycosylation reaction using Endo-M proceeds at RT in neutral phosphate buffer (pH 6.0) and reached maxima at around 30min. When Fmoc-Asn-GlcNAc (acceptor) was enzymatically reacted with Disialo-Asn (donor) in the presence of Endo-M, the ratio of Disialo-Asn-Fmoc (transglycosylation product) was almost comparable with the decreasing ratio of Fmoc-Asn-GlcNAc. Therefore, the transglycosylation activity of Endo-M from Disialo-Asn (donor) and fluorescent-Asn-GlcNAc (acceptor) was calculated from the decreasing ratio of fluorescent-Asn-GlcNAc. The order was NDA-Asn-GlcNAc>DBD-Asn-GlcNAc≅Fmoc-Asn-GlcNAc>NBD-Asn-GlcNAc≅DMEQ-Asn-GlcNAc>DNS-Asn-GlcNAc>PS-Asn-GlcNAc>FITC-Asn-GlcNAc. On the other hand, the activity with a fluorescent acceptor (DBD-PZ-Boc-Asn-GlcNAc), labeled to a carboxylic acid group in the Asn residue, was the strongest among the synthesized acceptors.

Keywords: Resolution of oligosaccharide; Transglycosylation with Endo-M; Fluorescecnt-Asn-GlcNAc; HPLC; Fluorescence detection

Investigation of micro-immobilised enzyme reactors containing endoglucanases for efficient hydrolysis of cellodextrins and cellulose derivatives by Claes Melander; Martin Bengtsson; Herje Schagerl�f; Folke Tjerneld; Thomas Laurell; Lo Gorton (pp. 182-190).

Cellulases hydrolysing the interior parts of cellulose, also called endoglucanases, were immobilised in micro-immobilised enzyme reactors (μIMER) made of porous silicon with the purpose of investigating the use of such μIMERs for hydrolysis of cellodextrins and soluble cellulose derivatives. The endoglucanases Trichoderma reesei Cel 12A (TrCel 12A) and Bacillus agaradhaerens Cel 5A (BaCel 5A) were covalently coupled to the surface of a silicon microchip through Schiff base formation. For characterisation cellohexaose was used as substrate for the immobilised enzymes. The characteristics of the μIMER were investigated by studying the product formation when varying the concentration, flow-rate, temperature and pH of the substrate solution. Hydrolysis was performed in the μIMER connected on-line to a chromatographic system, where the products were separated and detected using high-performance anion exchange chromatography (HPAEC) coupled to pulsed amperometric detection (PAD). A comparison of the hydrolytic pattern between BaCel 5A and TrCel 12A was carried out and the results show that the two investigated endoglucanases give specific hydrolytic patterns in the products formed that provide important information about the enzymes. The μIMERs are robust and can be employed continuously over a period of at least several days. Moreover, on appropriate storage, no activity loss is seen after 60 days. The ability of the BaCel 5A containing μIMER to perform hydrolysis of derivatised cellulose was also investigated using carboxymethyl cellulose (CMC) as substrate. Separation and detection were carried out using size exclusion chromatography (SEC) with refractive index detection (RI). The results show that the μIMERs are robust and can be employed for on-line hydrolysis of both cellodextrins and derivatised cellulose of high molecular weight.

Keywords: Micro-immobilised enzyme reactors; On-line enzymatic hydrolysis; Derivatised cellulose; Endoglucanases; Enzyme characterisation

Quantitative analysis of less soluble form IV in commercial carbamazepine (form III) by diffuse reflectance fourier transform spectroscopy (DRIFTS) and lazy learning algorithm by K. Kipouros; K. Kachrimanis; I. Nikolakakis; S. Malamataris (pp. 191-198).

Carbamazepine is a poorly soluble drug, with known bioavailability problems related to its polymorphism, and a form (C-monoclinic or form IV) less soluble than the pharmaceutically acceptable (P-monoclinic or form III) can be formed under various conditions, possible to occur during drug formulation. Therefore, quantitative analysis of form IV in form III is important to the drug formulators. In the present study, a fast and simple non-destructive method was developed for quantification of form IV in form III, by using DRIFTS spectral data subjected to the standard normal variate transformation (row centering and scaling) and to the lazy learning algorithm. Fast principal component (fast PCR) and partial least squares (PLS) regression methods of multivariate calibration were also used, which were compared with lazy learning. The lazy learning algorithm was performing better than the fast PCR and PLS methods (root mean squared error of cross-validation 1.318% versus 3.337 and 3.058%, respectively). Even with a small number of calibration samples it gave satisfactory predictive performance (root mean squared error of prediction <2.0% versus >3.3% of fast PCR and >2.6% of PLS), in the concentration range below 30% (w/w) of form IV. This is attributed to the capability of handling non-linearity in the relation of reflectance and concentration as well as to local modeling using a pre-selected number of nearest neighbor concentrations.

Keywords: Diffuse reflectance; DRIFTS; Carbamazepine; Crystal polymorphism; Lazy learning; Fast PCR; PLS

Determination of cercosporin (CER) phytotoxin isolated from infected peanut leaves by using adsorptive stripping square wave voltammetry by Nancy Cristina Marchiando; Mar�a Alicia Z�n; H�ctor Fern�ndez (pp. 199-203).

The adsorptive accumulation of cercosporin (CER) phytotoxin on glassy carbon (GC) electrodes from 1M HClO₄ aqueous solutions is used to detect and quantify the phytotoxin isolated from infected leaf tissue collected from field-grown peanut in five locations in southern regions of the Provinces of Córdoba and San Luis, Argentina. The adsorptive stripping square wave voltammetry (ASSWV) is employed to perform the quantitative determination of CER in naturally infected extracts.Thin layer chromatography (TLC) and HPLC were used to verify the presence of CER in extracts. Values of R_f=0.23 and R_f=0.15 were determined for CER by TLC when extracts were dissolved in ethyl acetate (EA) and acetone (Ac), respectively, while a retention time of 6.13min (Ac) was determined by HPLC.The recovery percentage of CER using ASSWV was determined by employing healthy peanut leaf tissue spiked with standard CER. The application of standard addition method was used to determine the recovery percentage as well as the CER contamination level in infected extracts. A recovery percentage of 93.27% was obtained with a relative standard deviation of 21.8% for a solution concentration of 1.04×10⁻⁶moldm⁻³ ( n=11). The limit of detection for a signal to noise ratio of 3:1 was about 6ppb and the quantitation limit was about 50ppb. The pondered relative standard deviation of 9.5% was calculated for the ASSWV method. Results found for CER contamination level in extracts through the electroanalytical method here proposed are in reasonable agreement with those values determined by using HPLC measurements.

Keywords: Cercosporin; Phytotoxins; Peanut; Square wave voltammetry; Adsorptive accumulation

A simple and sensitive assay of nucleic acids based on the enhanced resonance light scattering of zwitterionics by Zhanguang Chen; Weifeng Ding; Fenglian Ren; Jinbin Liu; Yizeng Liang (pp. 204-209).

A new assay of nucleic acids at nanogram level was established based on the enhanced resonance light scattering (RLS) signals of two zwitterionics cocamidopropyl hydroxysultaine (HSB) and lauryl betaine (BS-12). Under optimum conditions, the weak RLS signal of HSB is enhanced by nucleic acids, and the enhanced RLS intensity is proportional to the concentration of nucleic acids in the range of 0.02–7.3mgl⁻¹ for calf thymus DNA and 0.01–8.6mgl⁻¹ for fish sperm DNA. The detection limits were 1.5ngml⁻¹ for calf thymus DNA and 1.9ngml⁻¹ for fish sperm DNA. Plasmid DNA extracted from K-12-HB101 colt was determined with satisfactory results.

Keywords: Resonance light scattering (RLS); Zwitterionics; Plasmid DNA

Critical validation of a new simpler approach to estimate aqueous p K_a of drugs sparingly soluble in water by Rebeca Ruiz; Mart� Ros�s; Clara R�fols; Elisabeth Bosch (pp. 210-221).

A simple linear approach to estimate the aqueous p K_a of compounds sparingly soluble in water, mainly drugs, from solely one p K_a value determined in any methanol/water mixture is evaluated. The parameters (slope and intercept) of the linear relationships are related to the solvent composition and can be easily calculated according to the acidic or basic functional group of the compound. The method has been tested using the available literature data for phenols, aliphatic carboxylic acids, benzoic acid derivatives, both ortho and non- ortho substituted, amines and imidazole derivatives. The study involves the whole range of solvent composition and about one hundred compounds which show a wide variety of aqueous p K_a, from 1.3 to 12.4. The differences between calculated and previously published aqueous p K_a values are less of 0.2pK units. Consistent values are obtained whatever the composition of methanol/water mixture employed in the experimental measurements. The results support the usefulness of the tested method as a very simple approach to get reliable aqueous p K_a values for sparingly soluble drugs.

Keywords: Aqueous dissociation constants; p; K; _a; Methanol/water mixtures; Drugs; p; K; _a; extrapolation equations

Author Index (pp. 222-224).

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Analytica Chimica Acta (v.550, #1-2)