Check out our New Publishers' Select for Free Articles

Analytica Chimica Acta (v.535, #1-2)

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

Contents (pp. v-vii).

Calendar of forthcoming meetings (pp. n1-n3).

Filler Ad.: ACAEES (pp. ii).

Electrochemical measurement of endogenously produced nitric oxide in brain slices using Nafion/ o-phenylenediamine modified carbon fiber microelectrodes by Nuno R. Ferreira; Ana Ledo; Jo�o G. Frade; Greg A. Gerhardt; Jo�o Laranjinha; Rui M. Barbosa (pp. 1-7).

The role of nitric oxide (NO) as a regulatory diffusible molecule in the brain requires the evaluation of its concentration dynamics. In this work, we have developed microelectrodes suitable for real time electrochemical measurements ofNO in vitro. Nafion and o-phenylenediamine were used to modify the surface of carbon fiber microelectrodes (8μm diameter; ≈100μm tip length). Coating with Nafion was done at 170°C and the o-phenylenediamine solution was electropolimerized on the carbon surface.NO peak potential (+0.78±0.03V versus Ag/AgCl) was determined by square wave voltammetry withNO solutions prepared from the-generating compound diethylenetriamine/nitric oxide (DETA/NO). Microelectrodes were calibrated by amperometry at a potential of +0.90V versus Ag/AgCl. They showed good sensitivity (954±217pA/μM; n=6) and linearity toNO in the concentration range of 100–1000nM. They were also characterized in terms of detection limit (6±2nM, n=4), response time at 50% (1s), and selectivity against interferents, such as nitrite (780±84:1, n=6), ascorbic acid (750±187:1, n=6) or dopamine (18±2:1, n=6). Injections of 1mMl-glutamate, 1mMl-arginine, and 0.1mM N-methyl-d-aspartate did not produce changes in background current. Finally, the microelectrodes were used to measureNO concentration dynamics in rat hippocampal brain slices stimulated withl-glutamate and N-methyl-d-aspartate. Taken together, the data indicate that the microelectrodes exhibit the proper sensitivity and selectivity for studies ofNO dynamics in brain slices (in vitro) and possibly in whole brain (in vivo) recordings.

Keywords: Nitric oxide; Microelectrode; Hippocampus; Nafion; o; -Phenylenediamine

Adsorptive stripping voltammetric measurements of trace uranium at the bismuth film electrode by Lin Lin; Sompong Thongngamdee; Joseph Wang; Yuehe Lin; Omowunmi A. Sadik; Suw-Young Ly (pp. 9-13).

Bismuth-coated carbon-fiber electrodes have been successfully applied for adsorptive stripping voltammetric measurements of trace uranium in the presence of cupferron. The new protocol is based on the accumulation of the uranium–cupferron complex at a preplated bismuth film electrode held at −0.30V (versus Ag/AgCl), followed by a negatively-sweeping square-wave voltammetric waveform. Factors influencing the stripping performance, including the film preparation, solution pH, cupferron concentration, adsorption potential and time have been optimized. The resulting performance compares well with that observed for analogous measurements at mercury film electrodes. A detection limit of 0.3μg/L is obtained in connection to a 10min adsorption time. The response is linear up to 50μg/L and the relative standard deviation at 50μg/L uranium is 3.8% ( n=15; 2min adsorption). Potential interferences are examined. Applicability to seawater samples is demonstrated. The attractive behavior of the new ‘mercury-free’ uranium sensor holds great promise for on-site environmental and industrial monitoring of uranium.

Keywords: Bismuth film electrode; Uranium; Cupferron; Adsorptive-cathodic stripping voltammetry

Nanocomposite films containing Au nanoparticles formed by electrochemical reduction of metal ions in the multilayer films as electrocatalyst for dioxygen reduction by Minghua Huang; Yan Shen; Wenlong Cheng; Yong Shao; Xuping Sun; Baifeng Liu; Shaojun Dong (pp. 15-22).

Through electrostatic layer-by-layer assembly, AuCl₄⁻ anions and [tetrakis( N-methylpyridyl)porphyrinato] cobalt (CoTMPyP) cations were alternately deposited on indium tin oxide (ITO) substrates, and 4-aminobenzoic acid modified glassy carbon electrode. Electrochemical reduction of AuCl₄⁻ anions sandwiched between CoTMPyP layers leads to the in situ formation of Au nanoparticles in the multilayer films. Regular growth of the multilayer films is monitored by UV–vis spectroscopy. UV–vis spectroscopy, X-ray photoelectron spectroscopy and cyclic voltammetry confirm the formation of Au nanoparticles in the multilayer films after electrochemical reduction of AuCl₄⁻ anions. Atomic force spectroscopy verifies that the as-prepared Au nanoparticles are uniformly distributed with average particles diameters of 20–25nm. The resulting composite films containing Au nanoparticles with high stability exhibit high electrocatalytic activity for the reduction of dioxygen. Rotating disk electrode voltammetry and rotating ring-disk electrode voltammetry demonstrate the Au nanoparticles-containing films can catalyze two-electron reduction of O₂ to H₂O₂ in O₂-saturated 0.1M H₂SO₄ solution.

Keywords: Au nanoparticles; Electrochemical reduction; Layer-by-layer; Catalysis; Dioxygen reduction; Cobalt porphyrin

Analysis of major components of residual bacitracin and colistin in food samples by liquid chromatography tandem mass spectrometry by Della Wai-mei Sin; Clare Ho; Yiu-chung Wong; Siu-kei Ho; Alec Chun-bong Ip (pp. 23-31).

A selective and sensitive liquid chromatography tandem mass spectrometric (LC–MS/MS) method has been developed for simultaneous determination of residual bacitracin and colistin in bovine milk samples. Milk samples were deproteinized and extracted with a mixture of trichloroacetic/formic acid. After centrifugation, bacitracin and colistin in the extracts were separated on a reversed phase Alltima BDS C₁₈ column (250mm×2.1mm, 5μm) using a gradient elution programme of ammonium formate buffer (saturated ammonium formate:formic acid:acetonitrile:water, 1:5:50:950, v/v/v/v) and 0.1% formic acid in acetonitrile at 0.2mlmin⁻¹. Using electrospray LC–MS/MS with time-scheduled multiple reaction monitoring (MRM), identification and quantification of the major components of the two polypeptides were performed based upon the intensities of mass fragments from the respective doubly charged precursor ions: bacitracin A at 712→199amu and 712→227amu, and colistin A at 586→101amu, 586→202amu and 586→241amu, respectively, at the defined retention time windows and the matching of the specific tolerance of the relative abundance of the monitored ions. Polymyxin B, a polypeptide of colistin family, was employed as the internal standard. With an additional solid phase extraction procedure, the analytical method was applicable to the analysis of the two polypeptide antibiotics in animal's liver and tissue samples. The practical quantification limits of bacitracin A and colistin A were 100 and 50μgkg⁻¹; and mean intra-day ( n=7) and inter-day ( n=4) recoveries were in the range of 89.2–110% (R.S.D.<10%), and 90.4–112% (R.S.D.<13%) respectively in all matrices.

Keywords: Bacitracin; Colistin; LC–MS/MS; Bovine milk; Animal tissues

Screening, determination and confirmation of chloramphenicol in seafood, meat and honey using ELISA, HPLC–UVD, GC–ECD, GC–MS–EI–SIM and GCMS–NCI–SIM methods by Hao-Yu Shen; Hai-Liang Jiang (pp. 33-41).

Studies on screening, determination and confirmation of chloramphenicol (CAP) in 10 kinds of matrices, including seafood, meat, honey, etc. by enzyme-linked immunosorbent assay (ELISA), high-performance liquid chromatography (HPLC) with UV detector (HPLC–UVD) and gas chromatography in combination with electronic capture detector (GC–ECD) and mass spectrometry detector (GC–MS) in both electronic ionization mode (EI) and the negative ion chemical ionization mode (NCI) with selected-ion monitoring (SIM) acquisition method (GC–MS–EI–SIM and GCMS–NCI–SIM) have been carried out. Methods have been developed for both qualitative and quantitative detection of chloramphenicol (CAP). Extraction, clean-up, derivatization and analysis procedure have been optimized. The ELISA was carried out for screening, HPLC, GC and GC–MS were applied to determine and confirm CAP residue concentration in suspect samples. The ELISA procedure was carried out on an aqueous extract of the samples. Determination and confirmation of suspect samples were performed after extraction with phosphoric buffer solution (PBS, pH=6.88)/ethyl acetate, defatting with hexane, analyzed by HPLC or GC–ECD, GC–MS–EI, GC–MS–NCI method. Samples for GC analysis, were further clean-up with solid-phase extraction using LC-Si and LC-C18 cartridges and derivatized to form volatile derivatives by derivatization agent. These techniques are able to detect chloramphenicol residues at the level of 0.1–10μg/kg. Overall recoveries were 75–120% with R.S.D. values at 5.4–8.1%.

Keywords: Chloramphenicol (CAP); ELISA; HPLC–UVD; GC–ECD; GC–MS–EI–SIM; GCMS–NCI–SIM

ELISA qualitative screening of chloramphenicol in muscle, eggs, honey and milk: method validation according to the Commission Decision 2002/657/EC criteria by G. Scortichini; L. Annunziata; M.N. Haouet; F. Benedetti; I. Krusteva; R. Galarini (pp. 43-48).

A commercial enzyme-linked immunosorbent assay (ELISA) test has been applied for the qualitative screening analysis of chloramphenicol (CAP) in food of animal origin (muscle, eggs, milk and honey) at level corresponding to the European Union (EU) minimum required performance limit (MRPL) set for CAP analysis. Different analytical protocols were developed for the extraction and purification of CAP from the matrices under investigation. The ELISA kit validation study was performed according to the Commission Decision 2002/657/EC criteria established for qualitative screening methods. In this regard, the following parameters were determined: detection capability (CCβ), specificity/selectivity, applicability/ruggedness/stability. The CCβ value resulted below the MRPL (0.3μgkg⁻¹) for all the examined matrices. No relevant interferences from matrix effects or structurally related substances (florfenicol (FF) and thiamphenicol (THP)) were observed. Slight variations of some critical factors in the sample pre-treatment and clean up for muscle were deliberately introduced for ruggedness evaluation and they did not result in any negative effect on the CAP detection. In addition, the recovery rates and precision at three concentration levels (0.30–0.45–0.60μgkg⁻¹) were evaluated for all matrices under investigation. The proposed method is suitable for qualitative screening analysis of CAP in the above-mentioned food in conformity with the current EU performance requirements.

Keywords: Chloramphenicol; Muscle; Eggs; Milk; Honey; Enzyme-linked immunosorbent assay

Determination of selenium species in infant formulas and dietetic supplements using liquid chromatography–hydride generation atomic fluorescence spectrometry by Pilar Vi�as; Ignacio L�pez-Garc�a; Beatriz Merino-Mero�o; Natalia Campillo; Manuel Hern�ndez-C�rdoba (pp. 49-56).

The combination of liquid chromatography with hydride generation atomic fluorescence spectrometry was used as a technique for the speciation of selenite, selenate, selenocystine and selenomethionine. Two chromatographic techniques were used by connecting reversed-phase C₁₈ and ion-exchange columns in series, the mobile phase being a gradient from water to phosphate buffer. Se-compounds were extracted from the samples by a sequential technique which discriminated between water soluble and non-soluble selenium fractions. When the method was applied to the speciation of selenium in fortified foods, as infant formulas and dietetic supplements, selenite was the only species detected in the former while both selenite and selenoamino acids were detected in the latter. The reliability of the procedure was checked by analyzing the total selenium content of the samples by atomic fluorescence spectrometry and with a certified reference material, whole milk powder (CRM 8435). The method can be used for routine quality control applications.

Keywords: Selenium speciation; Liquid chromatography; Hydride generation atomic fluorescence spectrometry; Infant formulas; Dietetic supplements

EDTA determination in pharmaceutical formulations and canned foods based on ion chromatography with suppressed conductimetric detection by A.A. Krokidis; N.C. Megoulas; M.A. Koupparis (pp. 57-63).

A novel direct method for the determination of EDTA was developed and validated based on ion chromatography with suppressed conductimetric detection and anion exchange column (Dionex AS-14, 4mm×250mm). Depending on coexisting substances, suitable eluents are 10mM carbonate buffer/pH 11.0 or 10.5 ( t_R,EDTA=5.5 and 9.4min, respectively), and 120mM borate buffer/pH 8.5 ( t_R,EDTA=16.2min). For 10mM carbonate buffer/pH 11.0 and isocratic flow rate of 1.0mlmin⁻¹, a linear calibration curve was obtained from 2.7 to 100μgml⁻¹ ( r>0.998), with LOD 0.87μgml⁻¹ and %RSD 1.5 (5μgml⁻¹, n=9). Good resolution was achieved from commonly coexisting anions (chloride, metabisulphite, ascorbate and citrate), and other aminopolycarboxylic acids (EGTA, NTA and DTPA). The potential interference of pharmaceutical substances (caffeine, phenytoin, nembutal, tolbutamide, dicumarol, acetylsulphisoxazole and paracetamol) and metal cations (Ca²⁺, Cu²⁺ and Fe³⁺) was also examined. The ion chromatographic method was applied for the assay of EDTA in contact lens care solutions, synthetic injection drug solutions, canned mushrooms and mayonnaise, with simple treatment and good recovery (range 74–108%).

Keywords: EDTA; Ion chromatography; Suppressed conductimetric detection; Pharmaceuticals; Foods

Determination of free and total sulphur dioxide in wine by use of an amalgamated piezoelectric sensor by B. Palenzuela; B.M. Simonet; A. R�os; M. Valc�rcel (pp. 65-72).

A piezoelectric quartz crystal where the gold electrode is amalgamated with mercury is proposed as a sensor for sulphur compounds. The sensor is selective towards such compounds in both the vapour phase (particularly SO₂ and H₂S) and liquid phase. The dependence of its responsiveness to SO₂ on the mercury concentration, amalgamation conditions and experimental procedure is discussed. The sensor is especially stable under continuous-flow conditions. For application to the determination of free and bound sulphur dioxide in wine, a continuous-flow manifold was developed with a view to combine sample treatment and detection on-line. The results thus obtained were favorably compared with those provided by the Ripper recommended method. The reproducibility of analyses of real wine samples was better than 3.5% and recoveries ranged from 98 to 103%.

Keywords: Quartz crystal microbalance; Piezoelectric sensors; Mercury; Amalgamation; Sulphur dioxide; Wine

Use of magnetic resonance spectroscopy for the investigation of the CO₂ dissolved in champagne and sparkling wines: a nondestructive and unintrusive method by Gwennhael Autret; G�rard Liger-Belair; Jean-Marc Nuzillard; Maryline Parmentier; Anne Dubois de Montreynaud; Philippe Jeandet; Bich-Thuy Doan; Jean-Claude Beloeil (pp. 73-78).

It is demonstrated in this paper that an imaging spectrometer with the¹³C Magnetic Resonance Spectroscopy (MRS) technique is an original unintrusive and nondestructive method, perfectly adapted to determine the amount of CO₂ dissolved in a closed bottle of Champagne or Sparkling wine as well as the self-diffusion of CO₂ in this matrix. Two Champagnes and one Sparkling wine were analyzed on a 7T imaging spectrometer. It was necessary to use an imaging spectrometer with a large available bore to insert the bottle, localize the measurement and carry out¹H and¹³C spectroscopy with a good sensitivity. In the¹³C spectra, CO₂ and alcohol signals are well separated. By use of the quantity of ethanol acting as an internal reference, it was possible to deduce the CO₂ concentration. We determined the relaxation parameter T₁ of CO₂. Thanks to diffusion spectroscopy, the diffusion rate of the CO₂ in the closed bottle was also calculated. The method can easily be extended to study the CO₂ content in closed bottles of other sparkling drinks, like beers, sodas, and fizzy waters.

Keywords: Magnetic resonance spectroscopy; Champagne; Sparkling wines; Dissolved carbon dioxide; Diffusion coefficient

Infrared hyperspectral imaging for qualitative analysis of pharmaceutical solid forms by Y. Roggo; A. Edmond; P. Chalus; M. Ulmschneider (pp. 79-87).

A multi-spectral imaging spectrometer records simultaneously spectra and spatial information of samples. The infrared (IR) imaging system used was the Hyperion 3000 microscope (Bruker Optics) equipped with a focal plane array (FPA) detector. The detector allows creating a 64�64pixels image. For each pixel, a complete spectrum is acquired, which means that an IR image is in fact a data cube. Two methods for qualitative analyses of the data cube were applied: peak height and unfold principal component analysis (PCA). These methods were performed on two different pharmaceutical problems: the first one was the analysis of a contamination on the surface of a pharmaceutical solid dosage form and the second one was a set of six images of intact tablets with different dissolution properties. On the first data set, IR imaging and chemometrics identified the contamination (a concentration of wet dye). The imaging method applied on the second set allowed the determination of the main cause of the dissolution problem, which was the surface distribution of magnesium stearate. This study shows that infrared imaging can be useful for qualitative analysis and troubleshooting of pharmaceutical solid forms.

Keywords: Infrared imaging; Focal plane array detector; Unfold PCA; Solid pharmaceutical; Dissolution properties; Troubleshooting

Identification of the components of 16-membered macrolide antibiotics by LC/MS by Min Hu; Chang-Qin Hu (pp. 89-99).

We describe a method using liquid chromatography combined with positive electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) to identify the components of 16-membered macrolide antibiotics. Choosing three characteristic compounds (midecamycin A₁, midecamycin acetate, 4″-isovalerylspiramycin III), the mass fragment pathway of this group of antibiotics was determined. The characteristics of these kinds of compounds on chromatographic behavior and UV spectrum were revealed and confirmed by the components in six examples (kitasamycin, midecamycin, meleumycin, josamycin, acetylspiramycin, 4″-acylspiramycin), whose structure were already known. Utilizing this method, some components that had never been reported in these samples were characterized by LC/MS. In comparison to the classical method, the LC/MS method is simple, rapid, sensitive, specific and suitable to application in the fields of multi-components antibiotics analysis.

Keywords: Macrolide antibiotics; Leucomycins; Spiramycins; Component identification; LC/MS

Determination of thiazinamium, promazine and promethazine in pharmaceutical formulations using a CZE method by Francisco J. Lara; Ana M. Garc�a-Campa�a; Ferm�n Al�s-Barrero; Juan M. Bosque-Sendra (pp. 101-108).

We present the validation of a developed method using capillary zone electrophoresis (CZE) for quantitative analysis of three phenothiazines: thiazinamium methylsulphate (TMS), promazine hydrochloride (PMH) and promethazine hydrochloride (PTH) in pharmaceutical formulations. The influence of various parameters affecting the CZE separation (buffer pH and concentration, acetonitrile percentage, capillary temperature and applied voltage) was investigated by means of multivariate optimization using experimental designs so as to obtain the highest efficiency. The method allows the separation of the phenothiazines in 5.0min at optimized conditions: 100mM tris(hydroxymethyl)-aminomethane (Tris) buffer at a pH 8.0, 15% acetonitrile, capillary with 58.5cm in length at 25°C and a voltage of 30kV. Detection occurred at 254nm. Acceptable precision (relative standard deviation (R.S.D.) 5.3%) and linearity were achieved using the internal standard (IS) method. The limits of detection (LODs) were 2.8μgml⁻¹ for TMS and 3.3μgml⁻¹ for PMH and PTH. The method has been successfully applied in the analysis of pharmaceutical formulations.

Keywords: Capillary zone electrophoresis; Thiazinamium methylsulphate; Promazine; Promethazine; Pharmaceutical analysis

High resolution ICPMS as an on-line detector for flow field-flow fractionation; multi-element determination of colloidal size distributions in a natural water sample by Bj�rn Stolpe; Martin Hassell�v; Karen Andersson; David R. Turner (pp. 109-121).

Results are described from the first application of high resolution ICPMS coupled to flow field-flow fractionation (FlFFF–HR ICPMS), for the elemental characterization of small colloidal material (1–50nm hydrodynamic diameter) in a natural freshwater sample. Detection limits for a 45mL preconcentrated sample were 200ngL⁻¹ to 5μgL⁻¹ for major elements, 1–30ngL⁻¹ for most of the first row transition elements and <1ngL⁻¹ for rare earth elements. R.S.D. of the concentrations determined in five replicate measurements were less than 10% for 42 of the elements quantified. In total, 45 elements could be quantified, 15 more than were quantified in an earlier study performed with a quadrupole ICPMS. Direct on-channel preconcentration was used and the degree of preconcentration necessary was examined. The linearity between sample volume and calculated colloidal concentrations was good, but possible indications of sample losses were observed. Peak deconvolution analysis was carried out on some elements in order to obtain an estimate of the distribution of elements between organic carbon- and iron-rich colloids. Among the elements not previously studied, P, V and Ti were shown to associate strongly to iron-rich colloids, Br and I were exclusively bound to organic carbon colloids while As and Cd were equally distributed between the two. Sc corresponded to the pattern of lanthanides and Cr to the pattern of the other first row transition elements.

Keywords: Field-flow fractionation (FFF); ICPMS; Colloids

Analysis of coal by diffuse reflectance near-infrared spectroscopy by J.M. Andr�s; M.T. Bona (pp. 123-132).

Diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) in the near-infrared (NIR) range is a technique able to determine moisture, ash, volatile matter, fixed carbon, heating value and percentage of carbon, hydrogen, nitrogen and sulfur in coal samples. In this paper, spectra from 142 coal samples of different origins were acquired in absorbance, reflectance and Kubelka–Munk units. Physical effects due to particle size were minimized after applying different pre-treatments to each spectra. The resultant spectra were correlated to the above mentioned coal properties using partial least squares regression (PLS). Moreover, a principal component analysis (PCA) of the full set of samples suggested the use of more homogeneous sample sets. The results obtained for a homogeneous set improved the prediction ability of the procedure.

Keywords: Near-infrared spectroscopy (NIR); Coal analysis; Partial least squares (PLS); Pre-treatments effect

An automated screening method for the fast, simple discrimination between natural and artificial colorants in commercial saffron products by Mohammed Zougagh; Angel R�os; Miguel Valc�rcel (pp. 133-138).

A fast, simple screening method for discriminating between natural and adulterated saffron was developed that reduces the need for time-consuming techniques. The method uses a flow manifold where saffron samples containing adulterants in a phosphate buffer are passed through a column packed with cotton that retains the adulterants for subsequent elution with dilute ammonia. Samples testing positive for adulterants are subjected to a multivariate calibration technique such as partial least-squares regression (PLS) in order to quantify the adulterant analytes. This allows Methyl Orange, tartrazine and Ponceau-4R to be accurately quantified. The proposed method provides a yes/no overall response and allows the presence of adulterant species in positive samples to be confirmed. The calibration model was optimized by using an appropriate number of factors and the most suitable wavelength ranges to construct the Box–Behnken data matrix. The method was validated by application to saffron samples spiked with both individual adulterants and binary and ternary mixtures thereof.

Keywords: Screening method; Partial least-squares calibration; Saffron; Spectrophotometry

Chemiluminescent high-throughput microassay for evaluation of acetylcholinesterase inhibitors by M. Guardigli; P. Pasini; M. Mirasoli; A. Leoni; A. Andreani; A. Roda (pp. 139-144).

Current drug therapies for Alzheimer's disease (AD) are mainly based on acetylcholinesterase (AChE) inhibitors. However, such inhibitors may possess non-optimal pharmacological properties or cause adverse effects, therefore research for the development of new drugs is still in progress. In this paper, a rapid and simple chemiluminescent (CL) assay for the in vitro evaluation of AChE inhibitors in which the activity of AChE is measured through a series of coupled enzymatic reactions leading to light emission is described. The assay is performed in microtiter plates, both in the 96- and 384-well formats. In the latter format up to 30 compounds can be simultaneously analyzed in a very short time (the chemiluminescence measurement lasts 5min) and using small volumes of samples and reagents (the assay volume is less than 60μL), thus allowing high-throughput screening (HTS). The assay proved to be reliable, as demonstrated by the analysis of known AChE inhibitors, and the reproducibility of the results was satisfying for a screening assay (CV% in the order of 20%). It could therefore represent a valuable alternative to other methods for the preliminary evaluation of new potential AChE inhibitors.

Keywords: Acetylcholinesterase; Alzheimer's disease; Chemiluminescence; Enzyme inhibitor; High-throughput screening

An energy-transfer cataluminescence reaction on nanosized catalysts and its application to chemical sensors by Zhenyu Zhang; Ke Xu; Willy R.G. Baeyens; Xinrong Zhang (pp. 145-152).

When reductive gases pass over the surface of nanosized catalysts, a kind of chemiluminescence named cataluminescence (CTL) can be generated due to the production of excited intermediates. Here we report the observation of an energy transfer process between excited intermediates and the nanosized catalysts. The CTL is quenched when introducing Ho³⁺, Co²⁺ and Cu²⁺ into the catalyst, while new intensive CTL peaks appear when the catalyst is doped with Eu³⁺ or Tb³⁺. Further study indicates that the new CTL peak on Eu³⁺- or Tb³⁺-doped catalyst originates from the luminescence of the doped ions, excited by the energy transferred from excited intermediates produced during the reaction. Based on this novel energy-transfer CTL (ETCTL), an ethanol sensor is developed with Eu³⁺-doped nanosized ZrO₂ that is linear to ethanol concentrations from 45 to 550ppm, with the whole linear range lower than the lower limit of the previous CTL sensor. The ETCTL from Eu³⁺-doped in nanosized ZrO₂ shows 72 times higher sensitivity than the CTL from excited intermediates in the sensor. High selectivity and stability are also obtained for this sensor. The results also indicate that the main factor limiting the sensitivity of CTL sensor on pure catalyst may be the inevitable energy quenching of excited intermediates with the catalyst, which is artfully utilized in the present work by the introduction of Eu³⁺ that effectively absorbs this part of energy and transfers it into light energy.

Keywords: Cataluminescence; Energy-transfer; Chemical sensors

Chemiluminescence detection of amino acids using an Edman-type reagent, 4-(1′-cyanoisoindolyl)phenylisothiocyanate by Masaaki Kai; Mikio Morizono; Moses Njoroge Wainaina; Tsutomu Kabashima; Myung Koo Lee; Jianzhong Lu (pp. 153-159).

The 4-(1′-cyanoisoindolyl)phenylisothiocyanate (CIPIC) could be used as a chemiluminescence (CL) Edman-type reagent. Firstly, CL reaction conditions such as pH, buffer types, H₂O₂ concentration and organic solvents were optimized in detail. Secondly, the CL sensitivity of the derivative of Ala was compared with fluorescence and absorbance detections. Thirdly, the structures of the CL intermediate and emitter were elucidated by liquid chromatography–mass spectrometry (LC–MS) and NMR of CIPIC and its analogues after their CL reactions. Consequently, the thiohydantoin derivatives for 16 kinds of amino acids were separated and sensitively detected by CL with lower detection limits of 0.3–0.8pmol at a signal-to-noise ratio of 3, after the coupling reaction of amino acids with CIPIC and their cyclisation reaction.

Keywords: Chemiluminescence detection; Amino acid; Derivatisation; Edman-type reagent; CIPIC

Implementation of flow-through solid phase spectroscopic transduction with photochemically induced fluorescence: determination of thiamine by Javier L�pez-Flores; Mar�a L. Fern�ndez-De C�rdova; Antonio Molina-D�az (pp. 161-168).

For the first time, flow-through solid phase spectroscopic transduction has been implemented with photochemically induced fluorescence. The system developed allows the sensitive, selective and rapid determination of thiamine in the presence of the rest of B-complex vitamins. By UV-irradiation in a single-line flow injection device, thiamine is converted on-line into a strongly fluorescent photoproduct, which is retained on C₁₈ silica gel filling the flow cell placed in the detector. The fluorescence of the photoproduct retained on C₁₈ is measured at excitation and emission wavelengths of 367 and 443nm, respectively. The sorption of the photoproduct on the solid support improves noticeably sensitivity and selectivity with regard to previously reported photochemical–fluorimetric methods. Two calibration lines are constructed for 300 and 600μl of injection volume. Concentrations of the vitamin of 0.18–80ngml⁻¹ (300μl) and 0.09–50ngml⁻¹ (600μl) are determined; the detection limits are 55 and 28ngl⁻¹ and the R.S.D.s are 1.4 and 2.4%, respectively. The method allows the analysis of 52 and 36 samples per hour, respectively. The applicability of the method for the determination of thiamine in pharmaceuticals and human serum and urine was demonstrated by investigating the effect of potential interferences and by the analysis of real samples. The accuracy of the proposed method was checked by applying a reference method and a recovery test. Recovery levels were between 95 and 105%.

Keywords: Flow-through sensor; Photochemically induced fluorescence; Thiamine; C; ₁₈

Resonance Rayleigh scattering spectra of interaction of sodium carboxymethylcellulose with cationic acridine dyes and their analytical applications by Shao Pu Liu; Sa Chen; Zhong Fang Liu; Xiao Li Hu; Tai Shan Li (pp. 169-175).

In the near neutral media, sodium carboxymethylcellulose (NaCMC) can react with a cationic acridine dyes such as acridine yellow (AY) and acridine orange (AO) to form an ion-association complex. As results of the reaction, intensity of resonance Rayleigh scattering (RRS) is enhanced greatly and new RRS spectra appeared. The maximum scattering peaks exist at 285nm for AY–CMC and 315nm for AO–CMC. There is linear relationship between the relative intensity of RRS (Δ I) and concentration of NaCMC in the range of 0–1.5μgml⁻¹ for AY system and 0–3.0μgml⁻¹ for AO system. The method for determination of NaCMC has high sensitivity. The detection limits (3 σ) are 6.0ngml⁻¹ for AY and 41.7ngml⁻¹ for AO. Moreover, effects of foreign substances on determination of NaCMC have been investigated. It shows that the methods have good selectivity. A new method for the determination of NaCMC with AY or AO by RRS technique has been proposed. The method is sensitive, simple and fast.

Keywords: Sodium carboxymethylcellulose; Resonance Raleigh scattering; Acridine yellow; Acridine orange

Sequential spectrophotometric determination of paracetamol and p-aminophenol with 2,2′-(1,4-phenylenedivinylene) bis-8-hydroxyquinoline as a novel coupling reagent after microwave assisted hydrolysis by Hayati Filik; Mustafa Hayvali; Emine Kilic (pp. 177-182).

A new method to determine paracetamol and p-aminophenol in pharmaceutical products is presented. The purpose of this work is to introduce 2,2′-(1,4-phenylenedivinylene) bis-8-hydroxyquinoline (PBHQ) as a novel coupling agent. This developed method is based on the microwave assisted alkaline hydrolysis of paracetamol to p-aminophenol, which reacts in mildly alkaline medium with 2,2-(1,4-phenylenedivinylene)bis-8-hydroxyquinoline (PBHQ) as a novel coupling reagent. The formed product shows maximum absorbance at 650nm with molar absorptivity=3.4×10⁴lmol⁻¹cm⁻¹ and the method was linear in the 0.44–5.5mgl⁻¹ concentration range. The detection limit value was found to be 0.09μgml⁻¹. The stoichiometric composition of the dye is 2:1 (PAP:PBHQ). The effect of concentration of reactants and temperature on the coupling reaction was investigated. The proposed method is successfully adopted for the determination of paracetamol and p-aminophenol in various pharmaceutical preparations.

Keywords: Paracetamol; p; -Aminophenol; Spectrophotometry; 8-Hydroxyquinoline; 2,2-(1,4-Phenylenedivinylene) bis-8-hydroxyquinoline

Highly selective chromogenic ionophores for the recognition of chromium(III) based on a water-soluble azocalixarene derivative by Lilin Lu; Shufang Zhu; Xingzhong Liu; Zhizhong Xie; Xi Yan (pp. 183-187).

A new water-soluble chromium-selective chromogenic azocalix[4]arene had been synthesized from diazo coupling reaction between calix[4]arene and diazonium salts, and characterized by¹H NMR, IR,UV and element analysis. It possesses an absorbance maximum at 365nm in buffered aqueous environment, but addition of chromium(III) ion induced a weak blue shift to 350nm and a new absorption peak at 520nm (bathochromic shift of 155nm), exhibited an isosbestic point at 470nm. It is more noticeable that the absorbance at 520nm increases along with the augment of the concentration of chromium(III) ion. Based on this, a simple and selective spectrophotometric method was developed for the determination of chromium(III), in the range of 9.35×10^-4 to 4.45×10⁻³molL⁻¹ of chromium(III) the linear regression equation was determined to be: absorbance ( A)=0.001× C(10⁻⁴molL⁻¹ chromium(III))+0.2379, r=0.998, n=6.

Keywords: Chromium; Azocalix[4]arene; Chromogenic; Spectrophotometry

Determination of acetone in breath by Norio Teshima; Jianzhong Li; Kei Toda; Purnendu K. Dasgupta (pp. 189-199).

A light emitting diode (LED)-based photometric method for the measurement of gaseous acetone in human breath is presented. The detection chemistry is based on the reaction of acetone with alkaline salicylaldehyde to form a colored product, which absorbs in the blue and can be monitored with GaN-based LEDs with emission centered at 465nm. Gaseous acetone in breath is sampled with a porous membrane based diffusion scrubber (DS). The collected sample in the continuously flowing water carrier reacts with the reagent solution. We have used two approaches to collect breath acetone: the use of a face mask and a Mylar balloon as a collection bag. With the face mask approach, the expired air can be measured over long periods without major subject discomfort, balloon collection (5l) permits four measurements from a single fill. The LED-based liquid core waveguide (LCW) absorbance detector utilized sapphire ball lenses to prevent exposure of other optical components to a hot alkaline reagent solution. The high refractive index of the final mixture permitted the use of an inexpensive fluorinated ethylene copolymer (FEP Teflon^�) tube as a 10cm long LCW. The limit of detection (S/N=3) is 14ppbv gaseous acetone, and the linear range extends to 1.21ppmv. The concentration range in 11 volunteer subjects ranged from 176 to 518ppbv.

Keywords: Breath acetone; Diffusion scrubber; Liquid core waveguide; Absorbance detector

Microanalytical characterization of surface decoration in Majolica pottery by R. Padilla; O. Schalm; K. Janssens; R. Arrazcaeta; P. Van Espen (pp. 201-211).

This paper presents the results of the characterization of the surface finishing works in archaeological pottery fragments belonging to several Majolica types. The homogeneity, thickness and inclusions of both ground glaze and color decorations were, among other characteristics, inspected by scanning electron microscopy X-ray analysis (SEM-EDX). The identification of the main constituents in the decoration motifs was performed by means of scanning micro X-ray fluorescence analysis. Additionally, compositional classification based on non-destructive quantitative analysis of the ground glaze was performed.

Keywords: Micro X-ray fluorescence analysis; Scanning electron microscopy; Archaeological pottery provenance

Flow-injection system with glucose oxidase immobilized on a tubular reactor for determination of glucose in blood samples by Ana Carolina Ayupe de Oliveira; Vanessa Costa Assis; Maria Auxiliadora Costa Matos; Renato Camargo Matos (pp. 213-217).

A spectrophotometric method for the determination of glucose in blood sample is proposed. This method is based on selective oxidation of β-d-glucose tod-gluconate and hydrogen peroxide using an on-line tubular reactor containing glucose oxidase immobilized on Amberlite IRA-743 resin. The hydrogen peroxide, in the presence of phenol, 4-aminoantipyrine and peroxidase, produces a red compound ( λ_max=505nm). Beer's law is obeyed in a concentration range of 10–100μmol/L glucose with an excellent correlation coefficient ( r=0.9991), at pH 6.5, with a relative standard deviation (R.S.D)<3%. The flow rate of 2.0mL/min and injecting 200μl sample volumes was adopted. The detection limit of the method is 5.7μmol/l. Rectors prepared, presented high stability for at last 1 week under intense use in flowing solutions. The results show a simple, accurate, selective and readily applied method to the determination of glucose in blood sample. The analytical results obtained for these products by the proposed method are in agreement with those of obtained by the classical the spectrophotometric method with enzyme, free in solution.

Keywords: Glucose oxidase; Glucose; Blood; Flow-injection system; Spectrophotometric detection

Development of a flow-through enzyme-linked immunosorbent assay and a dipstick assay for the rapid detection of the insecticide carbaryl by Shuo Wang; Can Zhang; Yan Zhang (pp. 219-225).

Membrane-based competitive enzyme immunoassays in flow-through and dipstick format for the rapid detection of carbaryl were developed. A nylon membrane was coated with anti-carbaryl antibody and a carbaryl-horseradish peroxidase (HRP) conjugate was used as the labeled antigen for competitive assay of carbaryl. Both tests had visual detection limits of 10μgL⁻¹, sensitive enough to meet the requirements of regulatory agencies as a practical screening tool. Matrix interference was eliminated by appropriate dilution of sample extracts with buffer. With assay times of 5min (flow-through) and 15min (dipstick), these rapid tests can be useful as a quality control tool and can be used to qualitatively detect carbaryl.

Keywords: Carbaryl; Flow-through ELISA; Dipstick ELISA; On-site determination

A rapid and novel alternative to conventional sample treatment for arsenic speciation in rice using enzymatic ultrasonic probe by E. Sanz; R. Mu�oz-Olivas; C. C�mara (pp. 227-235).

This work proposes an arsenic speciation method, which reduces the sample treatment time from several hours, required by other extraction procedures, to only a few minutes. No organic solvents have to be used and several extraction steps can be avoided, thus diminishing possible sources of error. Total As was determined by ICP–MS and major arsenic species present in rice (As (III), As (V), methylarsonic acid (MMA) and dimethyarsinic acid (DMA)) were quantified by LC–ICP–MS. Different treatments for extraction were evaluated: aqueous, methanol and tetramethyl ammonium hydroxide (TMAH) extraction as well as enzymatic hydrolysis. Several parameters were optimised, such as sonication time, amplitude, immersion depth of the probe into the solution, extraction temperature, etc. Quantitative extraction for total arsenic (>95%) and 90% extraction for the sum of the arsenic species without species transformation were obtained by applying an enzymatic treatment using an aqueous mixture of protease XIV and α-amylase in only 3min. A disruption of the cell membranes due to the focused sonication energy, which alleviates enzyme attack, seems to be the responsible of such extraction enhancement.The method was applied to a rice sample used in an inter-comparison exercise (SEAS G6RD-CT2001-00473) and to two commercial rice samples. The method was validated for total arsenic extraction by analysing a certified reference material from NIST (SRM 1568a).

Keywords: Rice; Arsenic speciation; Enzymatic hydrolysis; Focused ultrasound probe; ICP–MS

Speciation of bio-available chromium in soils by solid-phase extraction and graphite furnace atomic absorption spectrometry by Guoxin Hu; Richard L. Deming (pp. 237-242).

Speciation of bio-available chromium in soils was performed using extraction with 0.05M EDTA followed by strong anionic solid-phase extraction. The step gradient elution technique with 0.1 and 0.5M NaCl as eluent in sequence was sufficient to separate Cr(III) and Cr(VI) with recoveries of 99.7 and 93.4%, respectively. During the determination of separated chromium species by graphite furnace atomic absorption spectrometry (GFAAS), 10% ammonium nitrate solution was co-injected with the sample to eliminate the interferences from the eluent matrix containing high concentrations of chloride. Linear calibration curves over the range of 0–15ngmL⁻¹ were obtained with good correlation coefficients ( R²=0.9976 for Cr(III)EDTA⁻, and 0.9897 for Cr(VI)). The sum of the chromium species determined after separation was in good agreement with total chromium from EDTA extraction of NIST soil standard SRM2709 (0.688μgg⁻¹ Cr(III), 0.127μgg⁻¹ Cr(VI), 0.742μgg⁻¹ total Cr) and a local soil sample (0.030μgg⁻¹ Cr(III), 0μgg⁻¹ Cr(VI), 0.053μgg⁻¹ total Cr).

Keywords: Chromium(III); Chromium (VI); Speciation; Bio-available chromium; Step gradient elution; Chemical modification

Optimization of aqueous acetylation for determination of hydroxy polycyclic aromatic hydrocarbons in water by stir bar sorptive extraction and thermal desorption–gas chromatography–mass spectrometry by Nobuyasu Itoh; Hiroaki Tao; Takashi Ibusuki (pp. 243-250).

Stir bar sorptive extraction (SBSE) using a 10mm-long stir bar coated with 24μl of polydimethylsiloxane (PDMS) in combination with the thermal desorption technique and gas chromatography–mass spectrometry was used for determining hydroxy polycyclic aromatic hydrocarbons (OH-PAHs), particularly mono and diOH-PAHs having two- to four-ring structures, in water samples. To improve the recovery for OH-PAHs, in situ derivatization with acetic anhydride was applied prior to SBSE. The optimal conditions for a 10ml water sample were attained with the addition of 100mg of sodium hydrogen carbonate, followed by the addition of 20μl of acetic anhydride and extraction for 360min. In the selected ion monitoring (SIM) mode, the limits of detection were found to range from 0.27ngl⁻¹ for 2-hydroxynaphthalene (as 2-hydroxynaphthalene acetate) to 25ngl⁻¹ for 1,4-dihydroxynaphthalene (as 1,4-naphthoquinone) (S/N=3). The low total recovery (<50%) of the entire procedure was mainly due to the low extraction efficiency of acetyl derivatives from water to PDMS, while the in situ derivatization step achieved more than 88% efficiency. Nine OH-PAHs, such as 1,4-naphthoquinone, 2-hydroxynaphthalene, 2,3-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,3-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, and 9-hydroxyphenanthrene, were detected in environmental samples under the optimal conditions. The detection of OH-PAHs in environmental water samples has not been reported so far.

Keywords: GC–MS; Hydroxy polycyclic aromatic hydrocarbons (OH-PAHs); Stir bar sorptive extraction (SBSE); Thermal desorption (TD); Water sample

Extraction of phenols and phenyl acetates with diethyl carbonate by Jacek Olejniczak; Jacek Staniewski; Jan Szymanowski (pp. 251-257).

Extraction of 11 selected phenols and their acetyl derivatives by diethyl carbonate was studied and compared with extraction into hexane and toluene. Diethyl carbonate is the most effective solvent and enables high recoveries of both phenols and their acetyl derivatives. The high recovery of phenols can be explained by the formation of a hydrogen bond between the hydroxyl group of phenols and the oxygen atom of the carbonate group. The extraction of phenols can be further increased in the presence of an electrolyte. The efficiency of extraction depends mainly upon phenol hydrophobicity and significantly increases with an increase in the solute molar volume and octanol–water partition coefficient.

Keywords: Solvent extraction; Phenols; Phenyl acetates; Abraham model; Diethyl carbonate; Capillary gas chromatography

Comparative classification study of toxicity mechanisms using support vector machines and radial basis function neural networks by X.J. Yao; A. Panaye; J.P. Doucet; H.F. Chen; R.S. Zhang; B.T. Fan; M.C. Liu; Z.D. Hu (pp. 259-273).

The performance and predictive capability of support vector machine (SVM) and radial basis function neural network (RBFNN) for classification problems in QSAR/QSPR were investigated and compared with several other classification methods such as linear discriminant analysis (LDA) and nonlinear discriminate analysis (NLDA). In the present study, two different data sets are evaluated. The first one involves the classification of four action modes of 221 phenols and the second investigation deals with the classification of the three narcosis mechanism of aquatic toxicity for 194 organic compounds. In both cases, the predictive ability of the SVM model is comparable or superior to those obtained by LDA, NLDA and RBFNN. The obtained results indicate that the SVM model with the RBF kernel function can be used as an alternative tool for classification problems in QSAR/QSPR.

Keywords: Support vector machine; Radial basis function neural network; Classification; Toxicity; Phenols; Narcosis mechanism

Net analyte signal–artificial neural network (NAS–ANN) model for efficient nonlinear multivariate calibration by Bahram Hemmateenejad; Mohammad A. Safarpour; A. Mohammad Mehranpour (pp. 275-285).

In recent years, artificial neural network (ANN) has been found major popularity in the analytical chemistry. This manuscript describes a simple and efficient ANN for modeling nonlinear spectral responses in spectroscopic multicomponent analyses. In this model, the spectral data were first subjected to net analyte signal (NAS) calculation and then the norm of the NAS vectors (||NAS||) was used as the input of the ANN model. Therefore, a simple model (NAS–ANN model) with only one node in input layer was obtained. A multilayer feed-forward neural network with back-propagation learning algorithm was used to process the nonlinear relationship between the ||NAS|| and concentration of analytes. The performance of the proposed model was evaluated by analysis of the simulated as well as the experimental data. In the simulated data, two source of nonlinearity including quadratic absorbance–concentration relationship and synergist effect were considered. In addition, the model was used for the simultaneous determination of three phenothiazine drugs including promethazine, chlorpromazine and perphenazine in their ternary mixture using conventional and derivative absorbance spectra. It was obtained that the proposed model could analyze the synthetic mixtures accurately. The model was compared with the PC–ANN model which is currently used for nonlinear multivariate calibration. The data confirmed that our model was simpler and produced more accurate results.

Keywords: Multivariate calibration; Artificial neural network; Net analyte signal; NAS–ANN

Multicomponent determinations using addition-generated reagent profiles and partial least squares regression by Rosa Garc�a; Guillermo L�pez-Cueto; Miren Ostra; Carlos Ubide (pp. 287-295).

The use of addition-generated reagent profiles is proposed for multicomponent determinations when the reactions between the reagent and analytes are slow. The oxidation of cysteine, methionine and homocysteine with dichromate in acidic medium has been used as the chemical system for experimental verification of some theoretical suppositions. The methodology tries to make the most of the differences in the kinetic behaviour. The continuous addition of dichromate (the reagent) to the sample including the amino acids provides the experimental data when the visible signal from dichromate is followed along time with a diode array spectrophotometer. The whole signal-time profile for the reagent is then used to characterize the sample, and partial least squares regression (PLSR) has been applied as calibration algorithm. Concentrations of amino acids between 10⁻⁴ and 10⁻³M have typically been used. In the present case, mean errors increase from individual determinations (between 2 and 5%) to binary (between 4 and 8%) and ternary mixtures (between 6 and 13%). This tendency can be expected to be of general application. Some validation with pharmaceutical products has been accomplished. A critical discussion on the practical interest of this application is finally included.

Keywords: Reagent profiles; Dichromate; Cysteine; Methionine and homocysteine determination; Multicomponent determination; Partial least squares regression

Determination of⁶³Ni and⁵⁵Fe in nuclear waste samples using radiochemical separation and liquid scintillation counting by Xiaolin Hou; Lars Fr�sig �stergaard; Sven P. Nielsen (pp. 297-307).

An analytical method for the determination of⁶³Ni and⁵⁵Fe in nuclear waste samples such as graphite, heavy concrete, aluminium and lead was developed. Different decomposition methods (i.e. ashing, acid digestion and alkali fusion) were investigated for the decomposition of the samples and for the separation of Fe and Ni from the matrix. Hydroxide precipitation was used to separate⁵⁵Fe and⁶³Ni from the matrix elements and ion exchange chromatography was used to separate⁵⁵Fe and⁶³Ni from the interfering radionuclides as well as from each other. The separated⁶³Ni was further purified by extraction chromatography. The purified⁶³Ni and⁵⁵Fe was then measured by liquid scintillation counting. The chemical yields of the separation procedures for⁵⁵Fe and⁶³Ni are above 90% and the decontamination factors for all interfering radionuclides are more than 10⁵. The detection limits of the analytical method for⁵⁵Fe and⁶³Ni are 0.018 and 0.014Bq, respectively. The methods developed were used in the analysis of⁵⁵Fe and⁶³Ni in heavy concrete, aluminium and lead from two concrete cores and graphite from thermal column in the Danish research reactor DR-2 and the results are presented in this paper.

Keywords: ⁵⁵; Fe; ⁶³; Ni; Radiochemical analysis; Decommissioning; Liquid scintillation counting

Analysis of reference materials by prompt γ-ray neutron activation analysis and evaluation of sample-dependent background by K. Sudarshan; R. Tripathi; A.G.C. Nair; R. Acharya; A.V.R. Reddy; A. Goswami (pp. 309-315).

A combination of internal mono-standard method and relative method of prompt γ-ray neutron activation analysis (PGNAA) was used for the non-destructive analysis of three certified reference materials (CRMs). The advantages of both the methods were effectively used in this combination methodology. The relative concentrations of different elements were determined by internal mono-standard method. In the internal mono-standard method, the use of multi-element standards and, identical irradiation and counting geometries are not required. The determined elemental concentrations were within ±10% of the certified values in most of the cases. In addition, one mixed sample of aluminosilicate and graphite was analyzed by PGNAA. The results show that PGNAA can be an attractive method of the non-destructive analysis of the major and minor elements present in the sample. The variation in the background contribution to the prompt γ-ray spectra due to the nature of the sample matrix has been critically evaluated. The suggestions for the background corrections in these cases are discussed.

Keywords: Prompt γ-ray neutron activation analysis; Internal mono-standard method; Reference materials

Comparison of alkaline fusion and acid digestion methods for the determination of rhenium in rock and soil samples by ICP-MS by Shigeo Uchida; Keiko Tagami; Ken Tabei (pp. 317-323).

A simple acid digestion method was studied in order to analyze many samples at once to understand Re behavior in the terrestrial environment, because, under normal laboratory conditions, digestion methods generally used, such as Carius tube digestions, Teflon vessel digestions and alkaline fusions, can handle only a small number of samples at one time to ensure complete sample digestion. In this study, the Re results for reference materials (RMs) obtained by the acid digestion method were compared with those by the alkaline fusion digestion method to get applicability of the acid digestion method for Re determination in soil by inductively coupled plasma mass spectrometry. Alkaline fusion was chosen for the comparison because it is known to have the highest capability to dissolve Re in geological materials among digestion methods.The average total Re recoveries measured using the¹⁸⁵Re spike for RMs, such as rock, soil and sediment, were 90.6±4.0% for alkaline fusion and 92.2±7.3% for acid digestion, showing no differences between them. However, Re results obtained by the acid digestion method were usually slightly lower than those by the alkaline fusion (Student's t-test, P<0.05); the concentration ratio of acid digestion to alkaline fusion was 0.85 on average. When the total Re content was higher than 0.2ngg⁻¹, the acid digestion method could dissolve about 80% of the sample Re. Although the acid digestion method is unable to dissolve all Re in the sample, however, the Re discharged to soils could be more extractable than the Re in the dissolution-resistant part; thus, the acid digestion method could be useful for obtaining Re levels in soil samples.

Keywords: Rhenium; ICP-MS; Soil; Rock; Alkaline fusion; Acid digestion

An empirical calibration for⁴He quantification in minerals and rocks by laser fusion and noble gas mass spectrometry using Cerro de Mercado (Durango, Mexico) fluorapatite as a standard by Jes�s Sol�; Teresa Pi (pp. 325-330).

An empirical calibration with a natural mineral standard (fluorapatite from Cerro de Mercado, Mexico) is proposed as a method to determine the⁴He concentration of mineral and rock samples. The procedure is based on the fusion of several aliquots of the fluorapatite standard with a well-spaced weight distribution in order to obtain a good correlation in coordinates of⁴He peak height versus fluorapatite weight. The weight is then converted to moles using the accepted mineral age (31.4Ma) and appropriate formula. Experimental peak height of⁴He for the unknown samples are converted to moles with the regression determined for fluorapatite. The procedure is fast and inexpensive, and both precision and accuracy are always below 10% and usually about 3–5%.

Keywords: Geochemistry; Geochronology; (U–Th)/He; Apatite

ESR identification of γ-irradiated redoxon and determination of ESR parameters of radicals produced in irradiated ascorbic acid by Mustafa Polat; Mustafa Korkmaz (pp. 331-337).

In the present work, electron spin resonance (ESR) identification of irradiated redoxon and its potential use as a normal and/or accidental dosimetric material were investigated in details. The ground redoxon samples exhibited a single weak resonance line of peak-to-peak width Δ H_pp=0.9mT appearing at g=2.0057. γ-Radiation produced many resonance lines beside four different intense lines (denoted as I₁, I₂, I₃ and I₄) of different spectral features in the studied dose range of 2.5–25kGy. Experimental dose–response curves associated with I₁, I₂, I₃ and I₄ resonance lines were found to follow an exponential function. From stability and kinetic studies at room and above room temperatures it was concluded that radicals contributing to I₃ and I₄ resonance lines were more stable than the radical species contributing to I₁ and I₂ resonance lines. Simulation calculations based on the room temperature ESR intensity data of an ascorbic acid (active ingredient of redoxon) sample irradiated at 10kGy was performed to determine the structure and spectral parameters of the radiation-induced radical species involved in the formation of experimental ESR spectrum of ascorbic acid. The contributions of these species to the ESR spectrum of irradiated redoxon were discussed.

Keywords: Dosimetry; ESR; Temperature; Kinetics; Ascorbic acid

Author Index (pp. 339-341).

Sections

Personal tools

Analytica Chimica Acta (v.535, #1-2)

Sections

Personal tools

Local resources

Analytica Chimica Acta (v.535, #1-2)