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Analytica Chimica Acta (v.548, #1-2)

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

Contents (pp. v-vi).

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

Unique molecular recognition property of bis-pyrene-modified β-cyclodextrin dimer in collaboration with γ-cyclodextrin by Masaya Toda; Nobuaki Ogawa; Hideaki Itoh; Fumio Hamada (pp. 1-10).

β-Cyclodextrin (β-CyD) dimer modified with two pyrene moieties, 6-(2-pyrenebutylate-aminoethyl)pyrenebutylate-amino-6-deoxy-bis-β-CyD (β-1) has been prepared to investigate the chemo-sensing ability for organic guests and the host–guest complexation behavior in the presence of γ-CyD. This fluorescent cyclodextrin dimer showed monomer and excimer emissions; the guest-induced emissions were observed as increase or decrease depending on the guest molecules. The sensing parameters,ΔIm/Im0 andΔIex/Iex0, were used to describe the sensing ability of β-1, whereIm0, I_m, I_ex andIex0 were fluorescence intensities of monomer and excimer emission, respectively, in the presence and absence of the guest andΔIm=Im−Im0 andΔIex=Iex−Iex0. This host particulary able to distinguish between ursodeoxycholic acid and chenodeoxycholic acid, which are related as diasteromer. It is observed that supramolecular association between the β-1 and γ-CyD was formed in the presence of 1-adamantanol and bisphenol A as a guest. In this work, we succeeded to make a new type of supramolecular assembly system based on hetero association between a guest, β-1 and γ-CyD.

Keywords: Cyclodextrin; Pyrene; Excimer; Supramolecular assembly

Molecularly-imprinted solid phase extraction of catechol from aqueous effluents for its selective determination by differential pulse voltammetry by C�sar Ricardo Teixeira Tarley; Lauro Tatsuo Kubota (pp. 11-19).

A polymeric sorbent based on molecular imprinting technology has been synthesized and applied to selectively extract catechol from water samples with subsequent determination by differential pulse voltammetry (DPV). The non-covalent polymer was prepared by bulk polymerization using catechol and 4-vinylpyridine as template and monomer, respectively. The effect of the flow and chemical variables associated to the performance of the solid phase extraction procedure was investigated and optimized using a 2⁵⁻¹ fractional factorial design as well as Doehlert design. A study of selectivity was carried out percolating a standard aqueous solution, which contained a mixture of catechol and five phenolic compounds (4-chloro-2-methoxyphenol, 4-aminophenol, 2-cresol, 2-methoxyphenol and 4-chloro-2-metoxyphenol) through the polymer packed into a cartridge followed by the elution with methanol/acetic acid (4:1, v/v) solution. Differential pulse voltammograms obtained from the eluted solution indicated that all compounds were retained on the sorbent since an overlapped peak was verified, showing the necessity to include a washing step. For this task, methanol, tetrahydrofuran, acetonitrile, dichoromethane and chloroform were checked as washing solvent, in which chloroform was able to establish the specific interaction between catechol and those sites of molecularly-imprinted polymers (MIP). Recovery higher than 95% was obtained for extraction of catechol even in the presence of structurally similar phenolic compounds. The procedure was further applied for catechol determination in aqueous effluent from paper mill industry and river water.

Keywords: Catechol; Molecularly-imprinted polymers (MIP); Differential pulse voltammetry; Solid phase extraction

Determination of hydrogen peroxide in rainwater in a miniaturised analytical system by Leanne Marle; Gillian M. Greenway (pp. 20-25).

The luminol chemiluminescence reaction within a microfluidic device was investigated to produce a miniaturised analytical system for the determination of hydrogen peroxide in rainwater. Enhancement of the chemiluminescence signal by 132% was achieved by means of using the mirror reaction to apply a reflective surface directly to the top of the microfluidic device, producing a limit of detection of 4.7nmolL⁻¹ with a small sample volume (20μL). This system was then used for the determination of hydrogen peroxide in rainwater samples during rainfall events showing the hydrogen peroxide concentration varied from 0.1 to 3.2μmolL⁻¹. The method was also applied to the analysis of hydrogen peroxide in snow demonstrating the hydrogen peroxide concentration varied from 0.2 to 0.5μmolL⁻¹ at ground level.

Keywords: Hydrogen peroxide; Rainwater; Luminol; Chemiluminescence; μTAS

On the solvent versatility in immobilized amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phase in high performance liquid chromatography: Application to the asymmetric cyclopropanation of olefins by Ashraf Ghanem; Hassan Y. Aboul-Enein (pp. 26-32).

The enantioseparation of a set of cyclopropanes derived from Meldrum's acid and 3,3,3-trifluoro-2-diazopropionate has been achieved on the new immobilized amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phase (Chiralpak IA) in high performance liquid chromatography (HPLC) using a mixture of n-hexane–2-propanol (90:10, or 99:1, v/v) as mobile phase with a flow-rate of 0.5ml/min and UV detection at 254nm. Due to its ability to withstand prohibited HPLC solvents like dichloromethane, an online HPLC equipped with a sensitive optical rotation detector for monitoring the optical activity of the racemic and enantioenriched cyclopropanes prepared via the Rh(II)-catalyzed asymmetric inter- and intramolecular cyclopropanations in dichloromethane is demonstrated. Direct analysis techniques without further purification, workup or removal of dichloromethane were summarized. The method provides an easy and direct determination of the enantiomeric excess of the cyclopropanes and selectivity of the catalyst used without any further work up.

Keywords: Amylose tris(3,5-dimethylphenylcarbamate); Chiralpak IA; Cyclopropanes; Enantioseparation; HPLC; Rhodium complexes

Measurement of unbound pravastatin in rat blood and bile on the perspective of hepatobiliary excretion and its interaction with cyclosporin A and berberine by Pi-Lo Tsai; Tung-Hu Tsai (pp. 33-40).

We develop a rapid and sensitive method using a microdialysis coupled with liquid chromatography to determine unbound pravastatin in rat blood and bile for additional pharmacokinetic study. Microdialysis probes were simultaneously inserted into the jugular vein toward heart and bile duct of male Sprague–Dawley rats for sampling in biological fluids following the administration of pravastatin through the femoral vein. The experiments were divided into three groups; in the control group, rats received pravastatin alone (1, 3 or 10mgkg⁻¹; i.v.). In the drug-treated groups, 10min prior to pravastatin administration, rats were given cyclosporin A (CsA; 10mgkg⁻¹, i.v.) or berberine (10mgkg⁻¹, i.v.). In the drug-pretreated group, berberine was orally administered for three consecutive days. The results indicate that pravastatin went through concentrative excretion into the bile against a concentration gradient based on the very high value of bile-to-blood distribution ratio of about 240. The active pravastatin efflux might be affected by P-gp because co-administration of CsA significantly decreased the pravastatin AUC in the bile in a dose-dependent manner. Conversely, taking berberine by acute concomitance or chronic 3-day pretreatment could increase the pravastatin AUC in the bile, which indicates the possible involvement of P-gp in the biliary excretion of pravastatin. Other transporter systems could not be excluded, but the present results give important evidence that pravastatin probably implicate P-gp transportation. According to the pharmacokinetic study, the drug–drug or herb–drug interactions of pravastatin should be warned with P-gp related drugs.

Keywords: Berberine; Hepatobiliary excretion; Microdialysis; P-glycoprotein; Pharmacokinetics; Pravastatin

Simultaneous determination of residual hormonal chemicals in meat, kidney, liver tissues and milk by liquid chromatography–tandem mass spectrometry by Bing Shao; Rong Zhao; Juan Meng; Ying Xue; Guohua Wu; Jianying Hu; Xiaoming Tu (pp. 41-50).

A method was developed for simultaneous determination of residues of 11 illegal natural and synthetic steroids in foods of animal origin including porcine meat, porcine liver, porcine kidney, chicken and milk. The samples were concentrated using an Oasis HLB solid phase extraction cartridge, followed by dual silica and amino-propyl cartridges for cleanup. The analytes were quantified by liquid chromatography using a phenyl column coupled to an electrospray ionization tandem mass spectrometer (LC–ESI-MS/MS) operating in negative mode for estrogens and in positive multiple reaction monitoring mode for androgens. The parameters of the mass spectrometer and the composition of mobile phase and additives were also optimized to enhance detection sensitivity. The limits of detection for target analytes ranged from 1 to 120ng/kg in different matrices.

Keywords: Hormone; Androgens; Estrogens; LC–ESI-MS/MS; Foods of animal origin

Poly(4-vinylpyridine) as a reagent with silanol-masking effect for silica and its specific selectivity for PAHs and dinitropyrenes in a reversed phase by Hirotaka Ihara; Megumi Fukui; Takamasa Mimaki; Atsuomi Shundo; Wei Dong; Mahnaz Derakhshan; Toshihiko Sakurai; Makoto Takafuji; Shoji Nagaoka (pp. 51-57).

This paper demonstrates that poly(4-vinylpyridine) is applicable as an effective masking reagent for silica to reduce undesirable side effects due to silanol groups. It also shows that this chemical modification brings about unique retention behaviors absolutely different from conventional ODS, which appear in molecular-shape selectivity for polycyclic aromatic hydrocarbons and in selectivity for position isomerism, especially for electron-withdrawing substitution compounds. Separation of 1,6- and 1,8-dinirtopyrenes as carcinogens is also described.

Keywords: Polymeric organic phase; Column liquid chromatography; Molecular-shape selectivity; Dipole–dipole interaction; π–π interaction; Dinitropyrene

A new method and apparatus for on-site detection of trace levels of chemical warfare agents by Shai Kendler; Adi Zifman; Natzach Gratziany; Amalia Zaltsman; Gad Frishman (pp. 58-65).

A pre-concentration/fast gas chromatograph for the sampling of toxic vapors from air was developed. Pre-concentration is performed by filtering the contaminated air through a tube containing absorbing material. The sample is thermally desorbed and separated on a short chromatographic column using air as a carrier gas. Detection is performed with a commercial hand-held chemical warfare agent detector. The effects of the airflow rate, sample volume and system temperatures on the analytical performance were studied. Detection of organophosphorus vapors at concentrations in the range 4×10⁻⁴ to 4×10⁻⁵mg/m³ was achieved within 2.5min. The ability to couple a portable detector to a pre-concentration/fast GC using air as a carrier gas encourages the development of a hand-held device for real-time on-site monitoring of low levels of CWA in the air.

Keywords: CWA; Pre-concentration; Fast-GC; On-site

Speciation analysis of mercury and tin compounds in water and sediments by gas chromatography–mass spectrometry following preconcentration on C₆₀ fullerene by J. Mu�oz; M. Gallego; M. Valc�rcel (pp. 66-72).

A simple method for the determination of mercury and tin compounds in water and sediments by solid-phase extraction–gas chromatography–mass spectrometry is proposed. The analytes are complexed with sodium diethyldithiocarbamate, retained on a C₆₀ fullerene column and eluted with ethyl acetate containing sodium tetra- n-propylborate as derivatizing reagent. The analytical figures of merit of the proposed method in the selective ion monitoring mode include: limits of detection from 0.8 to 1.5pgml⁻¹ (sample volume 50ml) and precision (as relative standard deviation) from 6.2 to 7.4%. The method is quite selective: the determination of mercury and tin species is subject to no interferences from metal ions such as Zn²⁺, Fe³⁺, Sb³⁺, As³⁺, Pb²⁺, Ni²⁺, Cu²⁺, Co²⁺, Mn²⁺and Cd²⁺. The accuracy of the method was evaluated from recovery values and the analysis of two standard reference coastal sediments (CRM 462 and CRM 580). The method was also applied to the determination of mercury and tin compounds in water and coastal sediment samples.

Keywords: Gas chromatography; Solid-phase extraction; Speciation; Fullerene

Thermodynamic characterization of a metallomesogenic stationary phase in gas chromatography by Jian-Lian Chen; Chuen-Ying Liu (pp. 73-78).

The nine representative dialkylsulfides are designed as probes to the assessment of the discotic copper complex-containing siloxane polymer as the GC stationary phase and the probable mechanism implicated. According to the isothermal retention data, which are transformed to the enthalpy, entropy and Gibbs energy losses as the gaseous probes partitioning in a mesophase and between mesophases, first we roughly observe the solutes with branched alkyl substituents were profoundly attracted to discotic lamellar phase, those with electron-releasing substituents to lamellar crystalline phase, and those with disk-like substituents to discotic hexagonal phase. To quantify the correspondent interactions between gaseous solutes and these mesophases, three controlling descriptors are chosen to account for the general dispersion, Lewis acid–base, and polarizability from unpaired-electrons within interactions. Through the multi-linear regression between enthalpy losses and solute descriptors, four linear equations, which correlation coefficients are larger than 0.926, are given to show the responsible extent that the possible interactions would be involved in and are agreeably consistent with the rough observation. The schematic representation of these mesomorphic structures clearly elucidates the connection between the proposed mechanisms and direct observations.

Keywords: Dialkylsulfide; Gas chromatography; Stationary phase; Thermodynamic; Metallomesogen; Multi-linear regression

Simultaneous determination of 22 volatile organic compounds, methyl- tert-butyl ether, 1,4-dioxane, 2-methylisoborneol and geosmin in water by headspace solid phase microextraction-gas chromatography–mass spectrometry by Sadao Nakamura; Shigeki Daishima (pp. 79-85).

A method for the simultaneous determination of 22 volatile organic compounds (VOCs), methyl- tert-butyl ether (MTBE), 1,4-dioxane, 2-methylisoborneol (2-MIB) and geosmin in water by headspace solid phase microextraction (SPME)-gas chromatography–mass spectrometry (GC–MS) is described. Three types of SPME fibers (carboxen (CAR)/polydimethylsiloxane (PDMS), divinylbenzene (DVB)/PDMS and 100-μm PDMS) were evaluated to achieve the method detection limits and linear range required in Japanese water regulation. A 100-μm PDMS was found to be the best coating to obtain a wide range of linearity for the target compounds in multiple-component system. CAR/PDMS and DVB/PDMS of adsorbent type fibers showed a narrow linear range for 22 VOCs, MTBE and 1,4-dioxane at the μg/l levels due to the limited capacity.The detection limits of this method were 0.01–0.05μg/l for 22 VOCs, 0.01μg/l for MTBE, 1.2μg/l for 1,4-dioxane, 0.6ng/l for 2-MIB and 0.3ng/l for geosmin. The recoveries of 22 VOCs and MTBE from a river water sample spiked at 1μg/l were between 93.7 and 104.0%, with R.S.D. values of between 1.7 and 9.5%. Those of 1,4-dioxane, 2-MIB and geosmin at 5μg/l, 10ng/l and 10ng/l, respectively, were 109.1, 95.9 and 97.4%, with R.S.D. values of 2.0, 5.6 and 1.8%. The method provided linear range from 0.1 to 100μg/l for 21 VOCs and MTBE, 0.1 to 50μg/l for m, p-xylene, 5 to 100μg/l for 1-4dioxane and 1 to 100ng/l for 2-MIB and geosmin.

Keywords: Water analysis; Volatile organic compounds (VOCs); Methyl-; tert; -butyl ether (MTBE); 1,4-Dioxane; 2-Methylisoborneol and geosmin; Solid phase microextraction (SPME); GC–MS

The capillary gas chromatographic properties of four β-cyclodextrin derivatives with allyl groups or propyl groups on 3-position or 6-position of β-cyclodextrin by Xueyan Shi; Pei Liang; Xiwu Gao (pp. 86-94).

Four cyclodextrin derivatives (CDs), 2,6-di- O-pentyl-3- O-allyl-β-cyclodextrin, 2,3-di- O-pentyl-6- O-allyl-β-cyclodextrin, 2,6-di- O-pentyl-3- O-propyl-β-cyclodextrin and 2,3-di- O-pentyl-6- O-propyl-β-cyclodextrin, which with allyl groups or propyl groups on 3-position or 6-position of β-cyclodextrin respectively, were synthesized. The separation abilities of the four CDs as stationary phases for capillary gas chromatography (CGC) were examined. The four CDs not only could separate the disubstituted benzene isomers well, such as o, m-, p-cresol and o-, m-, p-xylene isomers, the four CDs also possessed enantioseparation abilities to some enantiomers, such as enantiomers of allethrone acetate, propargyllone acetate, and 2-bromopropionic acid methyl ester etc.The enantioseparation results also showed that, while all of the four CDs could well separate some enantiomers among enantiomers tested, all of the four CDs could not separate the other enantiomers at all. The four CDs possessed similar enantioseparation abilities to enantiomers tested by us, and this indicated that not only the substitute position of allyl groups or propyl groups on 3-position or 6-position of CDs did not affect the enantioseparation greatly, the double bond of allyl groups also did not play key role in the enantioseparation. This is different from the results obtained on CDs substituted with acyl groups.

Keywords: Cyclodextrin derivatives; Chiral stationary phases; Capillary gas chromatography; Enantioseparation

Critical micelle concentration of surfactants in aqueous buffered and unbuffered systems by Elisabet Fuguet; Clara R�fols; Mart� Ros�s; Elisabeth Bosch (pp. 95-100).

Critical micelle concentration (CMC) of sodium dodecyl sulphate (SDS), lithium perfluorooctanesulfonate (LPFOS), hexadecyltrimethylammonium bromide (HTAB), tetradecyltrimethylammonium bromide (TTAB), and sodium cholate (SC), surfactants commonly used as pseudostationary phases in micellar electrokinetic chromatography (MEKC), have been determined by means of three different methods: MEKC, spectrophotometry, and conductometry. Determinations have been performed in water, and also in different concentrations of phosphate buffer at pH 7.0. CMC values ranging from 8.08 (water) to 1.99 (50mM phosphate buffer) mM for SDS, from 7.16 (water) to 2,81 (30mM phosphate buffer) mM for LPFOS, from 3.77 (water) to 1.93 (20mM phosphate buffer) mM for TTAB, from 0.91 (water) to ∼0.34 (20mM phosphate buffer) for HTAB, and around 13mM (20mM phosphate buffer) for SC, are obtained. The effect of the electrolyte concentration on the CMC, as well as the linear relationship between the electrolyte counter-ion concentration and the CMC are discussed. This linear relationship provides an easy way for users to estimate the CMC of a MEKC system, at a given electrolyte concentration. A comparison between experimental methods, as well as a discussion about the suitability of a given method for the determination of the CMC for a given surfactant system is also provided.

Keywords: Surfactants; Critical micelle concentration; Micellar electrokinetic chromatography; Conductometry; Spectrophotometry

Multi-element pre-concentration of heavy metal ions by solid phase extraction on Chromosorb 108 by Mustafa Tuzen; Mustafa Soylak; Latif Elci (pp. 101-108).

A multi-element preconcentration procedure for solid phase extraction on Chromosorb 108 as bathocuproinedisulfonic acid chelates and flame atomic absorption spectrometric determinations of some heavy metal ions in environmental samples is proposed in the present work. The influences of analytical parameters including pH of the aqueous solution, amounts of reagents, flow rates of sample and eluent solutions, sample volume etc. on the quantitative recoveries of copper, cadmium, lead, zinc, manganese, iron, chromium, nickel and cobalt ions were investigated. The effects of concomitant ions on the retentions of the analytes were also examined. The presented preconcentration procedure was applied to the determination of metal ions in reference standard materials (NRCC-SLRS 4 Riverine Water, SRM 1515 Apple leaves and GBW 07605 Tea) and some real samples including tap and river water, red wine, rice, black tea and honey.

Keywords: Solid phase extraction; Environmental samples; Atomic absorption spectrometry; Chromosorb 108

Development of the analytical method for 1,4-dioxane in water by liquid–liquid extraction by Yu-Mi Park; Heesoo Pyo; Song-Ja Park; Sun-Ku Park (pp. 109-115).

A convenient and simple method for the analysis of 1,4-dioxane in water was developed by liquid–liquid extraction combined with gas chromatography/mass spectrometry and applied to the water samples in Korea. Evaluation of the liquid–liquid extraction method was demonstrated by comparing with two extraction methods, which were solid-phase extraction and purge and trap method. They were referred to the standard methods for the examination of water in Japan and U.S. EPA methods. Liquid–liquid extraction was conducted by using methylene chloride and sodium chloride. This method was combined with gas chromatography/mass spectrometry. Recoveries showed in the range from 86 to 102% with relative standard deviation of 3.0 to 5.2%. The correlation coefficient of the linear regression curve was above 0.99 and method detection limit of 1,4-dioxane was 0.2ngmL⁻¹ for 20mL of water sample. The precision and accuracy were obtained within error rate of 9%. 1,4-Dioxane was detected in the treated water and raw water near Nakdong River from 0 to 240.0ngmL⁻¹. It has surveyed constantly with the national problem in Korea. The developed method may be suitable to analyze and observe 1,4-dioxane regularly.

Keywords: 1,4-Dioxane; Water; Liquid–liquid extraction; Solid-phase extraction; Purge and trap method

Analysis of liquid–liquid distribution constants of organophospohorus based extractants by Wiesław Apostoluk; Waldemar Robak (pp. 116-133).

Linear solvation energy relationships (LSER) analysis of distribution of organophosphorus based solutes between aqueous phase and organic solvents has been performed applying the Kamlet and Taft, as well as Leggett models of solvent effects.A correlation permitting the prediction of unknown and/or correction of uncertain values of Kabachnik induction constants from the structure of alkyl and alkoxyl substituents attached to phosphorus has been proposed.Dialkylorganophosphorus based acids in two-phase liquid systems are reasonably well described by the dependence of their dissociation and distribution constants on the ionic strength of the aqueous phase, the property parameters of solvents and structural properties of alkyl and alkoxyl substituents, respectively. The satisfactory results have also been obtained for the distribution constants of trialkylphosphine oxides influenced by the properties of solutes, solvents and ionic strength of the aqueous phase, respectively. The analysis of solvent effects upon the distribution constants of neutral esters of organophosphorus based acids has been performed for five solutes only, all of the low hydrophobicity, i.e. the first four members of homologous series of trialkyl esters of phosphoric acid and dimethyl methylphosphonate, respectively.

Keywords: Organophosphorus based extractants; Induction constants of alkyl and alkoxyl substituents; Dissociation constants; Distribution constants; Effect of diluents and ionic strength; Kamlet and Taft and Leggett models

Study of the luminescence behavior of seven quinolones on a paper substrate by Junfen Li; Jianqing Li; Shaomin Shuang; Chuan Dong (pp. 134-142).

Studies on the luminescence spectra behaviors of seven quinines on solid substrate (SS-RTP) were performed. Experimental conditions, such as heavy atom type, pH and drying time of the sample, etc. on solid substrate room temperature phosphorescence (SS-RTP) or solid substrate delayed fluorescence (SS-DF), were studied in detail. CdCl₂ could induce strongest RTP or DF emission of these quinolones. In addition, a comparative study on the spectral behavior of seven quinolones was given, including low temperature phosphorescence (LTP), low temperature fluorescence (LTF) and spectra methioned above. New determination methods for the analysis of seven quinolones by solid substrate room temperature fluorescence (SS-RTF), SS-RTP or SS-DF with filter paper as solid substrate were presented. Analytical characteristics of these methods of seven quinolones were studied. The linear dynamic ranges (LDR), the limit of detection (LOD) and the relative standard deviation (R.S.D.) were valued. Recoveries of seven quinolones in human urine samples were from 98.1% to 104.3%.

Keywords: Quinolones; Solid substrate room temperature phosphorescence; Solid substrate room temperature fluorescence; Solid substrate delayed fluorescence; Spectra behavior

Spectroscopic detection of halocarbons using modified Fujiwara reactions by D. Lynn Rodman; Nathan A. Carrington; He Qiu; Kisholoy Goswami; Zi-Ling Xue (pp. 143-147).

The Fujiwara reaction is the only known reaction for detecting halocarbons spectrophotometrically in the visible region, and it has been conducted with toxic, offensive-smelling pyridine and a strong base such as NaOH. New alternative approaches to conducting the Fujiwara reactions have been developed using solid pyridine derivatives and new bases for the detection of chloroform and carbon tetrachloride. The reactions of these halocarbons with 2,2′-dipyridyl (or 4,4′-dipyridyl) and tetra- n-butylammonium hydroxide ( n-Bu₄NOH) or potassium tert-butoxide (KO- t-Bu) were found to give colored species with detection limits of 0.17mg/L for chloroform and 0.50mg/L for CCl₄ (using 2,2′-dipyridyl and n-Bu₄NOH). The use of potassium tert-butoxide as the base in the Fujiwara reactions allows for the detection of the halocarbons in systems sensitive to water.

Keywords: UV–vis spectrometry; Fujiwara reaction; Chloroform; Carbon tetrachloride

Comparison of non-invasive NIR and Raman spectrometries for determination of alcohol content of spirits by Alison Nordon; Angela Mills; Ross T. Burn; Fiona M. Cusick; David Littlejohn (pp. 148-158).

The suitability of non-invasive NIR and Raman spectrometries for determination of % ethanol content has been investigated. Samples of whisky, vodka and sugary alcoholic drinks were analysed in 200mL (flat) and 700mL (round) glass bottles. The NIR spectrometer used double transmission measurements and was limited mainly to analysis of the signal produced at about 10,000cm⁻¹ by water and ethanol in the samples. The Raman measurements, produced using a 785nm laser, were based on a sharp signal from ethanol at 880cm⁻¹. A multivariate calibration model, based on a combined PCA–PLS algorithm, was required for analysis by NIR spectrometry, whereas a univariate calibration model was suitable for Raman spectrometry. Both techniques were limited to measurements in clear glass bottles as strong absorption/fluorescence occurred with coloured glass bottles. Bottle-to-bottle variations contributed the largest uncertainty to the measurements obtained for a 20% (v/v) ethanol solution in flat bottles: 2.3% R.S.D. for NIR spectrometry and 2.2% R.S.D. for Raman spectrometry. For 700mL round bottles, which have stricter manufacturing tolerances on glass thickness, the bottle-to-bottle variability for Raman spectrometry was 1.4% R.S.D. When spirit samples with ethanol concentrations in the range 19.9–61.7% (v/v) were analysed, the precision (average R.S.D.) was 0.4 and 0.5% for NIR (flat bottles) and Raman (round bottles) spectrometries, respectively, and the average accuracy was 2.1 and 2.9%, respectively. When a calibration model constructed from NIR data acquired on 1 day was applied to data sets collected over a 15-day period, the average error was 3.9%.

Keywords: Alcoholic beverages; Non-invasive analysis; Raman spectrometry; NIR spectrometry; Derivative spectrometry; Ethanol

Formation of inositol hexaphosphate monolayers at the copper surface from a Na-salt of phytic acid solution studied by in situ surface enhanced Raman scattering spectroscopy, Raman mapping and polarization measurement by Haifeng Yang; Yu Yang; Yunhui Yang; Hong Liu; Zongrang Zhang; Guoli Shen; Ruqin Yu (pp. 159-165).

Inositol hexaphosphate (IP₆) was proposed as an environmentally friendly reagent to prevent metal surface from corrosion through a self-assembled monolayers (SAMs) method. In situ surface enhanced Raman scattering (SERS) spectroscopic investigations revealed that the self-assembling of IP₆ at the roughened copper surface in a Na-salt phytic acid solution took two steps involving firstly self-cleaning the surface and then forming IP₆ monolayers. The features of the IP₆ monolayers were evaluated by the time-dependent Raman spectroscopic measurement, Raman mapping and electrochemical polarization experiments. Based on the calculation results for vibration spectrum of IP₆ molecule with PM3 method, a model for IP₆ molecule adsorbed chemically on the roughened copper via two co-planar phosphate moieties was suggested. The copper surface with the IP₆ monolayers presents the inhibiting action in a 0.1molL⁻¹ KC1 solution but the relative inhibition efficiency is of 41.2% because of the water co-adsorption.

Keywords: Na-salt phytic acid; Monolayers; Copper; In situ surface enhanced Raman scattering; Raman mapping; Tafel curves

Evaluation of slurry preparation procedures for the simultaneous determination of Hg and Se in biological samples by axial view ICP OES using on-line chemical vapor generation by Eder Jos� dos Santos; Amanda Beatriz Herrmann; Vera L�cia Azzolin Frescura; Adilson Jos� Curtius (pp. 166-173).

Seven slurry preparation procedures were evaluated concerning the simultaneous determination of Hg and Se by on-line chemical vapor generation coupled to axial view ICP OES, using: (1) aqua regia and sonication; (2) HCl, sonication and heating at 90°C; (3) tetramethylammonium hydroxide (TMAH); (4) H₂O₂, sonication, addition of HCl and heating at 90°C; (5) K₂S₂O₈, sonication, addition of HCl and heating at 90°C (6) TMAH, sonication, ozonation, addition of HCl and heating at 90°C; (7) Triton X-100, sonication, ozonation, addition of HCl and heating at 90°C. The concentrations of HCl and NaBH₄, used in the chemical vapor generation, in the different slurry media and in the slurry blanks, were optimized by factorial analysis. The calibrations were carried out using aqueous solutions in the same medium as the slurry, containing the analytes, Hg(II) and Se(IV), in the concentration range of 0.5–10μgL⁻¹. The procedures were applied initially to the certified material TORT-2 (Lobster Hepatopancreas) and all of them produced results for Hg in agreement with the certified value, according to the t-test for a 95% confidence level. However, for Se, results in agreement with the certified value were obtained only when Procedures 4 and 5 were used, indicating that either H₂O₂ or K₂S₂O₈ is required, most probably to break the Se bonds efficiently. Procedure 5, with detection limits (3s, n=10) of 0.08μgg⁻¹ for Hg and 0.10μgg⁻¹ for Se, for a sample mass of 20mg in a final volume of 15mL, was adopted and applied to the analysis of five certified reference biological materials and the tissues of six real oyster samples grown in the Santa Catarina Island coast. The obtained Hg and Se concentrations were in agreement with the certified values. The recommended procedure is simple, rapid and robust.

Keywords: Mercury; Selenium; Inductively coupled plasma optical emission spectrometry; Axial configuration; Chemical vapor generation; Slurry sampling; Biological samples

Re-examination of the MAGIC method to determine low orthophosphate concentration in seawater by Peggy Rimmelin; Thierry Moutin (pp. 174-182).

A new and detailed MAGIC25 procedure is proposed to determine low concentration of orthophosphate in seawater. By preconcentrating phosphate 25 times, the procedure allowed detection of nanomolar concentration in seawater with low concentration of particles (detection limit=0.8�0.5nM). The centrifugation step was considerably reduced (from 60 to 10min) in comparison to previous MAGIC method. The calibration coefficient was determined by performing procedural and extra calibration curves and a previously unknown matrix effect in the MAGIC procedure was revealed. Its omission leads to a 12% underestimation of the phosphate concentration. The necessity of pre-filtration was demonstrated and a turbidity blank was measured to avoid overestimation even in the oligotrophic Mediterranean Sea water. The absence of filter reactivity with phosphate (contamination or retention) was verified. A synthetic reagent blank was proposed to simplify procedure in comparison to previous MAGIC method. The slow down of phosphomolybdenum blue complex was observed in the MAGIC concentrate and this results in a minimum reaction time of 30min. The sensitivity (ratio of signal/noise) showed a three-fold improvement in comparison to the more recent nanomolar methods. Interferences of arsenate and silicate, commonly observed in the classic phosphomolybdic blue spectrophotometry, were undetectable. The MAGIC25 method appears reliable, sensitive, accurate and relative easy to use during oceanographic cruises. Therefore, MAGIC25 procedure is a useful tool for oceanograph chemists to be used instead of the classic phosphomolybdic blue method when concentration is below 200nM.

Keywords: Spectrophotochemical analysis; Phosphate; Seawater; Mediterranean sea

Speeding up enzymatic hydrolysis procedures for the multi-element determination in edible seaweed by Carlos Pe�a-Farfal; Antonio Moreda-Pi�eiro; Adela Bermejo-Barrera; Pilar Bermejo-Barrera; Hugo Pinochet-Cancino; Ida de Gregori-Henr�quez (pp. 183-191).

A novel accelerated enzymatic hydrolysis by mean of ultrasonication has been developed and applied as sample pre-treatment for edible seaweed in order to determine total levels of As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn. Three enzymes, α-amylase, pepsin and trypsin, have been evaluated and the released metals from seaweed have been measured by inductively coupled plasma–optical emission spectrometry (ICP–OES). Variables such as pH, sonication temperature, ultrasound frequency, ionic strength, hydrolysis time, extracting volume and enzyme mass were simultaneously studied by a Plackett–Burman design (PBD). Results have showed that there had not been any significant variable (confidence interval of 95%) affecting the conventional or the ultrasound-assisted enzymatic hydrolysis processes. This fact is attributed to the high salt content in seaweed, which generates a solution with a high ionic strength. The ultrasound-assisted enzymatic hydrolysis can be completed in 30min when using an ultrasound frequency at 35kHz. Quantitative recoveries were only reached when using pepsin, while recoveries close to 80% were obtained for the use of α-amylase and trypsin. The methods were validated by analyzing IAEA-140/TM, Fucus – Sea Plant Homogenate – and NIES-09, Sargasso, certified reference materials.

Keywords: Ultrasound-assisted enzymatic hydrolysis; Multi-element determination; Edible seaweed; Inductively coupled plasma–optical emission spectrometry

A novel potentiometric sensor for selective determination of theophylline: Theoretical and practical investigations by Siavash Riahi; Mir Fazllolah Mousavi; S. Zahra Bathaie; Mojtaba Shamsipur (pp. 192-198).

A novel theophylline potentiometric sensor is prepared, characterized and used in pharmaceutical analysis. The sensor is based on a PVC membrane containing dibutyl phthalate as plasticizer, 2,6-bis(phenyl)-4(phenyl)3H-thiopyran (PPT) as ionophore and oleic acid (HOA) as additive. A linear response in the range of 1.0×10⁻⁶ to 1.0×10⁻²M of theophylline with a slope 54.5±0.4mV per decade was established. The optimum pH range was 5.3–7.3 and the lower detection limit was 5.5×10⁻⁷M of theophylline. The electrode displays a good selectivity for theophylline with respect to a large number of common foreign inorganic and organic species, amino acids and drugs. The membrane sensor was successfully applied to the determination of theophylline in its tablets. A theoretical study based on the optimum angle and distance between theophylline and PPT molecules was conducted. These investigations were carried out based on ab initio calculations, to estimate the pair wise interaction energy between the two molecules.

Keywords: Theophylline selective electrode; PVC membrane; 2,6-Bis(phenyl)-4(phenyl)3H-thiopyran; ab initio calculations; Pharmaceutical analysis

Amperometric determination of chemical oxygen demand with flow injection analysis using F-PbO₂ modified electrode by Jiaqing Li; Luoping Li; Lei Zheng; Yuezhong Xian; Shiyun Ai; Litong Jin (pp. 199-204).

An electrochemical detection system with an F-PbO₂ modified electrode for flow injection analysis to determine chemical oxygen demand (COD) was proposed and experimentally validated. The measuring principle was based on the current response on the modified electrode which was proportional to the COD value. Under the optimized experiment condition, the linear range was 100–1200mgl⁻¹, and the detection limit was 15mgl⁻¹. This method was successfully applied to determine the COD in samples without pretreatment. It was characterized by short analysis time, simplicity, low environmental impact, a limited reagent consumption and easy automation. Additionally, the COD values obtained from the proposed and conventional methods agreed well as demonstrated by the high significant correlation between the two sets of COD values ( R=0.9985, n=25).

Keywords: F-PbO; ₂; modified electrode; Flow injection analysis; Amperometric detection; Chemical oxygen demand (COD)

An amperometric immunosensor based on immobilization of hepatitis B surface antibody on gold electrode modified gold nanoparticles and horseradish peroxidase by Ying Zhuo; Ruo Yuan; Yaqin Chai; Ying Zhang; Xue lian Li; Qiang Zhu; Na Wang (pp. 205-210).

An amperometric immunosensor based on the gold nanoparticles (nano-Au) and horseradish peroxidase (HRP)-modified gold electrode for the determination of hepatitis B surface antigen (HBsAg) has been developed. The novelty of the methodology was the first use of the HRP, instead of bovine serum albumin (BSA), to block the possible remaining active sites of the gold nanoparticles monolayer, avoid the nonspecific adsorption and amplify the response of the antigen-antibody reaction at the same time. Tests performed with this immunosensor showed good linearity and sensitivity when it was evaluated on several clinical samples. The system was optimized to realize a reliable determination of HBsAg in the range of 2.56–563.2ng/ml with a detection limit of 0.85ng/ml. Moreover, the proposed sensor was comparable to BSA-blocked immunosensor in terms of the linearity and sensitivity.

Keywords: Amperometric enzyme immunosensor; Gold nanoparticles (nano-Au); Hepatitis B; Horseradish peroxidase (HRP)

Author Index (pp. 211-212).

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Analytica Chimica Acta (v.548, #1-2)