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Analytical and Bioanalytical Chemistry (v.374, #7-8)

Thanks to referees in 2002 (pp. 1171-1173).

Laser-based double beam absorption detection for aggregation immunoassays using gold nanoparticles by Nguyen Thanh; Harrison J. Rees; Zeev Rosenzweig (pp. 1174-1178).

A laser-based double beam absorption detection system for aggregation immunoassays has been developed. The assay was based on the aggregation of gold nanoparticles that are coated with protein antigens in the presence of their corresponding antibodies. The aggregation of the gold nanoparticles results in an absorption change that is monitored at 635 nm using the double beam spectrometer. The noise level of the spectrometer is 1×10^–6arbitrary units. This corresponds to a tenfold improvement in comparison to commercial absorption detectors and is comparable with previously reported more complicated laser-based absorption spectrometers. The dye Nile-Blue-A was used to test the analytical performance of the system. A limit of detection of 3×10^–8M Nile-Blue-A was observed. The relative standard deviation between consecutive measurements was lower than 1.5%. The system is suitable for field applications of aggregation-based immunoassays.

Keywords: Diode laser Double beam absorption spectroscopy Gold nanoparticles Aggregation immunoassay

Application of restricted access material (RAM) with precolumn-switching and matrix solid-phase dispersion (MSPD) to the study of the metabolism and pharmacokinetics of Verapamil by Markus Walles; Jürgen Borlak; Karsten Levsen (pp. 1179-1186).

In the pharmaceutical industry, studies of the metabolism and pharmacokinetics of drugs are important routine applications which require the analysis of the precursor drug and its metabolites in various biological matrices, such as plasma, serum, urine, cell culture media and tissue samples. In this study, two new and simple methods of sample preparation were optimized and validated: on the one hand, a column-switching technique with a restricted access material (RAM) was used to analyze biological fluids, and on the other hand, matrix solid-phase dispersion (MSPD) was applied to the extraction of analytes from tissue samples. Identification of the metabolites was done with a LC–MS system (ion trap in the MSⁿmode) coupled both on-line (RAM) and off-line (MSPD).Using the common calcium antagonist Verapamil, it is shown that these two methods allow rapid identification of phase I and phase II metabolites from biological samples and are suitable for pharmacokinetic and pharmacodynamic studies of pharmaceuticals in biological matrices.

Keywords: Restricted access material Matrix solid-phase dispersion Metabolism Pharmacokinetics Verapamil

Determination of lomefloxacin by terbium sensitized chemiluminescence method by Li-Hua Nie; Hui-Chun Zhao; Xu Wang; Lin Yi; Yan Lu; Lin-Pei Jin; Hui-Min Ma (pp. 1187-1190).

A simple, rapid and sensitive chemiluminescence (CL) method was proposed for the determination of lomefloxacin (LFX). This method is based on the fact that the weak CL from the redox reaction of Ce⁴⁺-Na₂SO₃ can be greatly enhanced by the complex of Tb³⁺-LFX. The CL intensity is directly proportional to the concentration of LFX in the range 2.0×10^–9 to 1.0×10^–5 mol L^–1, and the detection limit (S/N=3) is 1.1×10^–9 mol L^–1. This method has been applied to the detection of LFX in pharmaceutical preparation, urine and serum samples. Recoveries were in the range 95–105%. The CL mechanism of Ce⁴⁺-Na₂SO₃-Tb³⁺-LFX system was proposed to be an intermolecular energy transfer from excited SO₂ ^* to LFX and an intramolecular energy transfer from LFX to Tb³⁺.

Keywords: Lomefloxacin Terbium Chemiluminescence Energy transfer Flow injection

Development of a robust technique for sampling volatile metal(loid)s in wetlands by Britta Planer-Friedrich; Jörg Matschullat; Broder J. Merkel; Gerhard Roewer; Peter Volke (pp. 1191-1198).

The formation of volatile organic and inorganic metals and metalloids in aquatic environments is a known, but not very intensively investigated, process. Several techniques have been developed over the past 10 years to determine these trace components. These techniques are of limited use in wetland environments, where samples have to be taken from the soil-water interface, and require an immediate sample analysis due to thermodynamic instabilities of the volatile metal(loid)s. This paper presents an innovative sampling technique for total concentrations of volatile metal(loid)s in wetlands, based on an in situ gas-water separation via a porous PTFE membrane and stabilising the volatile metal(loid)s in a liquid sorbent (NaOCl solution). Samples may thus be collected even at remote sites, where longer storage times have to be accounted for. The sampling system was tested by means of a laboratory facility simulating the generation of arsine and dimethyl arsine under abiotic conditions as well as under field conditions. Results for sampling efficiency, reproducibility, and long-term storage are presented. Application of the sampling system in the field is shown.

Keywords: Volatile metal(loid)s Volatilisation Wetlands Liquid sorbents Arsenic Hydride generation

Determination of azadirachtin and fatty acid methyl esters of Azadirachta indica seeds by HPLC and GLC by Nutan Kaushik (pp. 1199-1204).

A simple and economical method has been developed to estimate the azadirachtin content and fatty acid composition of neem kernels. Neem kernels are crushed and soaked overnight in ethanol. The extract obtained is analysed by HPLC after filtering through a 0.22 µm membrane. The peaks are separated using acetonitrile–water (40:60) 1 mL min^–1 as the mobile phase on an RP-18 column and monitored at 214 nm. For the determination of fatty acid composition, the fatty acids are directly transmethylated in the kernel powder by heating with methanol–acetyl chloride–benzene (20:1:4, v/v) for 1 h in a water bath. The fatty acid methyl esters (FAMEs) obtained are extracted in hexane and analysed using GLC. The separation of the FAMEs is achieved using an RH-Wax column using temperature programming, 170–200 °C at 2 ° min^–1. The peaks are detected using an FID. Both the methods do not require any clean up or defatting of seeds. This results in faster, easier and more economical sample preparation.

Keywords: Neem Azadirachta indica Azadirachtin Fatty acids HPLC GLC

Application of headspace–mass spectrometry for differentiating sources of olive oil by Marcos I. Lorenzo; Pérez J. Pavón; Fernández M. Laespada; García C. Pinto; Moreno B. Cordero; L. Henriques; M. Peres; M. Simões; P. Lopes (pp. 1205-1211).

In the present work we propose the use of headspace-mass spectrometry (HS-MS) for the characterisation of monovarietal olive oils, an issue of interest when the origin of an oil has to be determined. The HS-MS procedure involves the direct introduction of the sample into a vial, headspace generation and automatic injection of the volatiles into a mass spectrometer. The results were compared with those obtained using more conventional approaches, including chromatographic, spectrophotometric and other types of analysis. Linear Discriminant Analysis (LDA) was applied to the data obtained with both analytical methodologies to achieve the differentiation of the three types of samples. The proposed method is faster and cheaper than those usually employed for edible oil analysis and no sample preparation is required. Additionally, the measuring process is simple and the results obtained from chemometric treatment are 100% correct as regards classification and prediction, making it an appropriate method for routine control.

Keywords: Headspace–mass spectrometry Electronic olfactometry Chemometric treatment Monovarietal oils

A spot test for aqueous phosphate by color band formation by Yoshiaki Kiso; Kazumichi Kuzawa; Yoshihiro Saito; Toshirou Yamada; Masahiro Nagai; Yong-Jun Jung; Kyung-Sok Min (pp. 1212-1217).

Phosphate is generally analyzed by color intensity of phosphoantimonylmolybdenum blue (PAMB): especially by a spot test based on spectrophotometric or visual determination. Visual determination is one of the simplest and most inexpensive methods; however, it is believed to be of low precision. In this work, we have developed an alternative phosphate spot test, where phosphate concentration is measured by the color band length of PAMB formed in a detection tube similar to a gas detection tube. The color band is formed by the entrapment of the hydrophobic ion pair of PAMB and quaternary ammonium ions in the column; we demonstrated that this color band length correlates quantitatively with the phosphate concentration. In order to optimize the measurement performance, systematic investigations have been carried out for various experimental parameters such as phosphate concentration, preparation conditions of the column packing material, the type of support material (either silica-gel or PVC), the solution feeding conditions (filtration or penetration), and volume of the sample solution. The effects from some co-existing components were also studied for the measurement of real samples.Determination of phosphate concentrations in actual wastewaters was successfully carried out by this method, indicating that the quantification range achievable was of 3–18 mg PO₄ L^–1 without dilution prior to the analysis. No interference was observed from suspended solid (SS) and organic pollutants (COD, TOC) during the wastewater analysis. Because of the simplicity and rapid processing of the samples (not requiring any special instruments) this newly developed method can be applied to the on-site analysis of wastewater.

Keywords: Phosphate analysis Spot test Detecting tube Color band Phosphoantimonylmolybdenum blue

A new method for determination of hydroperoxides in cellulose by D. Kočar; M. Strlič; J. Kolar; B. Pihlar (pp. 1218-1222).

A new chromatographic method for determination of hydroperoxides in cellulose is described, whereby the sample is dispersed in phosphate buffer solution (pH 7) of FeCl₃, EDTA and the hydroxyl radical scavenger, N,N'–(5–nitro,1,3-phenylene)bisglutaramide. The reaction time, concentration of reagents and chromatographic conditions for subsequent separation and quantification of hydroxylated products are optimised. The limit of detection is 0.14 µmol L^–1 H₂O₂ which corresponds to 2.1 µmol hydroperoxides per kg of cellulose (mass of sample: 0.4 g). It was shown that in the concentration range of H₂O₂ up to 15 µmol L^–1 the method gives linear response and that adsorption of reaction products on fibres is negligible. For cellulose samples, this corresponds to a linear range of 2.1–225 µmol of hydroperoxides per kg. Due to possible side reactions of hydroxyl radicals in the suspension of analyte, it is recommended that the standard addition technique is used. In purified cotton cellulose, the steady state concentration of hydroperoxides at room conditions was found to be 15.1±1.5 µmol kg^–1.

Keywords: Cellulose Hydroxyl radicals Hydroperoxides Fenton reaction HPLC Oxidation

Multivariate calibration applied to simultaneous chemiluminescence determination of cobalt and chromium by P. Campíns-Falcó; L. Tortajada-Genaro; S. Meseguer-Lloret; F. Bosch-Reig (pp. 1223-1229).

The simultaneous determination of chromium and cobalt in water samples has been studied. Chemiluminescence registers based on the luminol–hydrogen peroxide reaction have obtained by a batch procedure. PLS algorithms have employed to model the time-response (formation and destruction of emitter).The influence of the presence of two metals and the non-linearity relationship between response and concentration have been evaluated in the signal. Different experimental designs and the selection of variables have been tested. The calibration set has been selected based on two criteria: unicomponent and/or bicomponent standard solutions and the slope calculated from linear univariate calibration. The response has been modelled providing high percentages of explained variance, robust models and low prediction errors.The proposed methodology has been validated using test standard solutions and a standard reference material of fresh water. Accurate results have proved the advantages of this method for the simultaneous determination of chromium and cobalt in water samples.

Keywords: Chemiluminescence Chromium and cobalt determination Water Luminol-hydrogen peroxide reaction Simultaneous analysis

Determination of As in environmental solid matrix by E. Beccaloni; L. Musmeci; E. Stacul (pp. 1230-1236).

In line with recent European environmental guidelines on biomasses, one of the most important parameters to take into account is the As concentration, especially when present in biomasses and complex matrices. The goal of the present study is to give information about possible technical-analytical problems during the determinations of such elements by means of different instrumental spectroscopy techniques, in particular inductively coupled plasma atomic emission (ICP-AES) and atomic absorption (AAS), using two different wavelengths, 188.98 nm and 193.70 nm.In the Laboratory of Hygiene of National Institute of Health in Italy, a specific study has been carried out concerning the determination of As contents in environmental solid matrices, using as reference material BCR 141 R, represented by a calcareous soil. In particular, whereas recovery tests did not show particular drawbacks, difficulties were met in the As detection in reference material. Spectral interference was seen during determination by ICP-AES and matrix interference during determination by AAS, in particular using ETAAS with deuterium background correction and HAAS. Using ETAAS with Zeeman background correction at 193.70 nm, the As line did not show particular matrix interference during the reading of samples.A ring test involving two more laboratories and another certified reference material (IAEA-356 in marine sediment matrix) produced important information about problems of under/over estimation of data. Two different instrumental techniques, ICP-MS and HAAS, confirmed previous data , i.e., overestimation for inductively coupled plasma mass spectrometry and that As values achieved by HAAS were of the same order as the references, but affected by considerable standard deviation.In the light of this study, data achieved on the environmental matrices investigated suggest that the critical step in As determination is the instrumental reading, rather than the mineralization process. Further, each of the methods proposed, apart from ETAAS with Zeeman background correction, presents its own peculiar drawbacks and no particular advantage over other techniques.

Analytical investigation of plasma-treated carbon fibres by H. Bubert; W. Brandl; S. Kittel; G. Marginean; D. Toma (pp. 1237-1241).

As-grown and heat-treated vapour grown carbon fibres (VGCF) in the as-prepared state, washed in HCl/H₂O, and treated in O₂ plasma for different periods have been investigated by means of XPS and scanning electron microscopy (SEM). The surface energy of the carbon fibres before and after plasma treatment was determined from the wetting contact angle. Washing introduced hydroxyl, carbonyl and carboxyl groups onto the fibre surfaces and oxygen plasma treatment increases the total atomic concentration of oxygen up to 17%. This is in good agreement with the value of the polar component of the surface energy. Plasma treatment also enhanced the fibre surface porosity (by etching).

Keywords: Vapour grown carbon fibre (VGCF) X-ray photoelectron spectroscopy Plasma treatment Surface analysis

Comparison of spark OES methods for analysis of inclusions in iron base matters by Heinz-Martin Kuss; Susanne Lüngen; Gregor Müller; Uwe Thurmann (pp. 1242-1249).

A statistical model for the evaluation of the emission intensities of single spark discharge spectra on three different spark OES instruments (ARL 4460, OBLF-QSN 750, SpectroLab) was developed for the analysis of non-metallic inclusions in steel. In total, the raw measurement data consists of several thousand data points (intensities), about 2000 per element channel. A histogram (frequency distribution of pulse height intensities) of inclusion-forming elements like Al, Ti and Mn performed in intensity classes and the related frequencies contain the information of the measurement. Measurement of a pure iron sample with slag powder rubbed into the surface by single spark emission spectrometry changes the originally (nearly) symmetrical histogram for inclusion related element signals to higher intensities. Thus, the known asymmetry of the histograms for steel samples is explained by the presence of inclusions.A sum of Gaussian fits representing the histogram was expected to express the different elemental species and inclusion sizes by using the variables mean, standard deviation and area of the peak containing the information of the measurement. Even a less complex approximation using a sum of two Gaussian fits is not practicable for the Al, Ti and Mn channel and the three spectrometers due to too many variables in the fitting function resulting in a large scattering. Coincidences of high signals in different element channels could be seen only in terms of MnS.A further attempt was to form the second differential of the logarithmic normal distribution and to compare the resulting partial areas below the functional graph to get information about the asymmetry of the fitting function of the original histogram. Two different procedures to evaluate the effect of the inclusion concentration on the size of the partial areas were applied to measurements on a set of synthetic samples with different concentrations of aluminium oxide in micro alloy steel. The results of both evaluation procedures correlate significantly with the inclusion concentrations. Electronic Supplementary Material is available if you access this article at http://dx.doi.org/10.1007/s00216-002-1595-1. On that page (frame on the left side), a link takes you directly to the supplementary material.

Keywords: Aluminium oxide Non-metallic inclusions Single pulse evaluation Spark OES Steel cleanness

Polarographic study on poly α-L-glutamic acid-Cd²⁺,Co²⁺ complexes in the helix–coil pH region by Atsushi Asano; Chrissy M. Sullivan; Akira Yanagisawa; Hiroki Kimoto; Takuzo Kurotsu (pp. 1250-1255).

Interactions between poly α-L-glutamic acid (PGA) and metal ions Cd²⁺, Co²⁺ were studied by direct current polarography. The diffusion currents of these ions decreased sharply in the presence of PGA in the pH region from 5.0 through neutral. A corresponding increase in the helix content of the PGA–metal ion complex was revealed by CD measurements on the same solutions. Helix contents determined by polarography were in good agreement with those by CD in the neutral pH region. On the contrary, the decrease of current in lower acidic pH regions was independent of helix formation and suggested that metal ions coordinate to sporadically-dissociated carboxylate groups to cause aggregation of the intra and/or inter polymer chains. The diffusion current of the ions, therefore, is a parameter sensitive to the conformational changes of PGA from acidic through neutral pH region.

Keywords: Polarography Circular dichroism Poly glutamic acid Helix–coil transition.

The online removal of dissolved oxygen from aqueous solutions used in voltammetric techniques by the chromatomembrane method by Regina Reinke; Jürgen Simon (pp. 1256-1260).

The applicability of the chromatomembrane method for the removal of dissolved oxygen from solvents used in voltammetric measurements was investigated. The chromatomembrane cell combined with a flow-through system allows an online deaeration of solutions. These experiments employed a mercury film electrode as working electrode and differential pulse anodic stripping voltammetry as the measuring method. Different eluents with adequate supporting electrolyte (without analyte) were measured to determine the background current, whether any contribution of oxygen is detectable. Voltammograms of eluents deaerated with the chromatomembrane method are compared to those of eluents purged with nitrogen for several minutes immediately before the measurement. No differences in the background currents can be observed when defined flow rates of eluent and nitrogen are maintained. Determinations of cadmium and lead even indicate the high efficiency of this method.

Keywords: Anodic stripping voltammetry Chromatomembrane cell Online-deaeration Mercury film electrode Flow-injection analysis

TiO₂ sol-gel derived amperometric biosensor for H₂O₂ on the electropolymerized phenazine methosulfate modified electrode by Xin Xu; Jiequan Zhao; Dechen Jiang; Jilie Kong; Baohong Liu; Jiaqi Deng (pp. 1261-1266).

A novel hydrogen peroxide biosensor was developed based on the immobilization of horseradish peroxidase (HRP) in a TiO₂ sol-gel matrix on an electropolymerized phenazine methosulfate (PMS) modified electrode surface. Such membranes are of interest due to their high surface area, biological compatibility, and ease of fabrication. HRP entrapped in the TiO₂ matix was stable and retained its activity to a large extent. Cyclic voltammetry and amperometric measurements were employed to demonstrate the feasibility of electron transfer between immobilized HRP and the glassy carbon electrode via electropolymerized PMS. The influence of various experimental parameters such as operating potential, pH, temperature, and stability was investigated for optimum analytical performance. The biosensor provided a wide linear calibration range from 4.0×10^–6 M to 1.0×10^–3 M, with a detection limit of 8.0×10^–7 M at a signal-to-noise ratio of 3. The sensor retained 80% of its original activity after two months of operation.

Keywords: TiO2 sol-gel Biosensor Phenazine methosulfate Horseradish peroxidase

Ruthenium/rhodium modified gold electrodes for the amperometric detection of hydrogen peroxide at low potentials by Dirk Janasek; Walter Vastarella; Uwe Spohn; Nico Teuscher; Andreas Heilmann (pp. 1267-1273).

Electrodes of ruthenium/rhodium deposited as thin layers on gold foils were investigated. Ruthenium layers were radio frequency (r.f.) magnetron sputtered and the rhodium layers were made by vacuum evaporation. Hydrogen peroxide could be detected using the cathodic reduction at potentials lower than +170 mV or the anodic oxidation at higher potentials. Under flow injection conditions, H₂O₂ was detected between 1 and 1000 µM at a potential of –100 mV and between 2 and 500 µM at a potential of +250 mV vs. Ag/AgCl/0.4 M KCl. The electrodes also showed high operational stability and selectivity against many electroactive substances. The selectivity against dissolved oxygen was investigated.

Keywords: Amperometric detection Hydrogen peroxide Vacuum deposition Ruthenium/Rhodium electrode layer

A coulometric method for determining substances that interfere with the measurement of water in oils and other chemicals by the Karl Fischer method by Sam A. Margolis; Jeffery Paulsen; Edward Park (pp. 1274-1281).

In order to fulfill a need to measure water in crude oils containing materials that interfere with the measurement of water by the Karl Fischer method, by reacting with iodine or iodide, a coulometric method has been developed and validated using 0.1 mol L^–1 Sodium thiosulfate as a calibrant. These interfering substances were measured in water-mass-equivalents, which were expressed as the mass of water that reacts with an equal mass of iodine in the Karl Fischer method. The SO₂-free reagent that has been modified reacts quantitatively with sodium thiosulfate, cysteine and ascorbic acid but does not react with vinyl acetate. The level of interfering substances was measured in five transformer oils (including Reference Materials RM 8506 and RM 8507), a high and a low sulfur crude oil (Standard Reference Materials SRM 2721 and SRM 2722 respectively), a white oil, a high-vacuum oil and a high-viscosity base-stock oil. One oil contained less than 10 mg kg^–1 (water-mass-equivalents of interfering substances in oil) and two oils (RM 8507 and Drakeol 35) contained no measurable amount of interfering material (<0.2 mg kg^–1). SRM 2271, a sour crude oil contained 834 mg kg^–1 (standard deviation (SD)=25 mg kg^–1) (water-mass-equivalents of interfering substances in oil). Approximately 20% of this material was volatile and an additional 20% appeared to undergo some degradation (possibly oxidation) once the oil was exposed to air. These results indicate that this is a general method for measuring substances in oils that react with iodine and that it is capable of measuring in a variety of oils, using commercial instrumentation, interfering substances that inflate water measurements.

Keywords: Karl Fischer Interfering substances Crude oils Transformer oils Coulometry

Influence of experimental parameters on the determination of antimony in seawater by atomic absorption spectrometry using a transversely heated graphite furnace with Zeeman-effect background correction by Jean Cabon (pp. 1282-1289).

Spectroscopic and electrothermal conditions for the determination of antimony in seawater using a transversely heated graphite furnace with Zeeman-effect background correction have been optimized with the use of an a priori calculation of the detection limit. The lowest limit of detection was obtained with a 2 nm spectral curvatures bandwidth and the use of an electrodeless discharge lamp; however, these experimental conditions resulted in strong premature curvature of calibration curves. Pd(NO₃)₂ can be recommended as a chemical modifier because seawater interference effects are minimized and pretreatment curves up to 1500 °C can be used permitting the removal of the major part of the saline matrix before atomization. Under optimized spectroscopic and electrothermal conditions the obtained limit of detection of Sb in seawater was about 0.4 µg L^–1.

Keywords: Atomic absorption spectrometry Graphite furnace Antimony Seawater

Silicon determination in milk by electrothermal atomic absorption spectrometry using palladium as chemical modifier by P. Bermejo-Barrera; M. Barciela-Alonso; R. Domínguez-González; A. Bermejo-Barrera; J. Cocho de Juan; J. Fraga-Bermúdez (pp. 1290-1293).

A direct method for silicon determination in milk samples by Electrothermal Atomic Absorption Spectrometry was developed. Palladium was used as chemical modifier at a concentration of 610 mg L^–1; with this modifier, silicon was stable up to 1800 °C. The precision and accuracy of the method were investigated. The detection limit was 16.2, 2.7 and 7.2 µg L^–1 for cows' milk, human milk and infant formula, respectively. The method was applied to silicon determination in 17 infant formula samples, 13 human milk samples and 12 cows' milk samples.

Keywords: Silicon Milk Electrothermal atomic absorption spectrometry

Slurry sampling for the determination of thallium in soils and sediments by graphite furnace atomic absorption spectrometry by R. Dobrowolski (pp. 1294-1300).

The analytical conditions for thallium determination in soils and sediments by slurry sampling graphite furnace atomic absorption spectrometry were studied and optimized. Elimination of a strong background for soils rich in organic materials by application of tungsten carbides coated graphite tubes/platforms was studied in detail. Tungsten carbides increased the maximum permissible pyrolysis temperature from 300 to 900 °C. The mechanism of tungsten carbide formation on different graphite surfaces was proposed. Application of a strong basic anion-exchange resin for interference elimination in thallium determination in marine sediments was described. Calibration was performed directly using aqueous standards both for soil and sediment analysis. Analysis of CRM confirmed the reliability of the approach. The precision and accuracy of thallium determination by the described method for soils and sediments was acceptable. A characteristic mass of 13.8 pg was obtained and the limit of detection for the proposed method was around 0.06 µg g^–1 Tl.

Keywords: Thallium determination Slurry sampling Graphite furnace atomic absorption spectrometry Soils Sediments

Direct determination of Cr and Cu in urine samples by electrothermal atomic absorption spectrometry using ruthenium as permanent modifier (R1) by Kátia Lelis; Cristina Magalhães; Clélia Rocha; José of Silva (pp. 1301-1305).

In this study Ru, deposited thermally on an integrated platform pyrolytic graphite tube, is proposed as a permanent modifier for the determination of Cu and Cr in urine samples by electrothermal atomic absorption spectrometry. The samples were diluted 1:1 with nitric acid (1% v/v). Pyrolysis and atomization temperatures for spiked urine samples were 1,100 °C and 1,900 °C respectively for Cu, and 1,400 °C and 2,500 °C respectively for Cr. For comparison purposes, the conventional modification with Pd+Mg was also studied. The sensitivity for Ru as permanent modifier was higher for the two analytes. The characteristic masses were 7.3 and 17.7 for Cr and Cu. The detection limits (3σ) were 0.22 and 0.32 µg/L, for Cr and Cu, respectively. Good agreement was obtained with certified urine samples for the two elements.

Keywords: Electrothermal atomic absorption spectrometry Permanent ruthenium modifier Urine Copper Chromium

Column preconcentration and FAAS determination of copper, iron, nickel and zinc using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol–tetraphenylborate–naphthalene adsorbent by Patrick J. Pancras; Bal Puri (pp. 1306-1311).

A solid co-precipitated material obtained from an ion-pair of 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) and tetraphenylborate (TPB), and microcrystals of naphthalene has been tried as an adsorbent for the column preconcentration of copper(I), iron(II), nickel(II) and Zn(II). The retention of the metal ions was found to be maximum and constant in the pH range 3.0–8.0 for Cu, 3.8–7.5 for Fe, 4.5–7.5 for Ni and 8.5–11.0 for Zn. The elements were determined by FAAS after dissolving the metal along with the adsorbent in an organic solvent (10 mL of DMF). The characteristic concentration for 1% absorption was found to be 0.0332, 0.0536, 0.0537 and 0.0142 (aqueous medium 0.0512, 0.0638, 0.1294 and 0.0216) µg mL^–1 for Cu, Fe, Ni and Zn, respectively. The calibration plot was linear in the range 1.5–20.0, 2.0–38.0, 2.5–25.0 and 0.5–15.0 µg in the final 10 mL of DMF solution for Cu, Fe, Ni and Zn, respectively. Various parameters such as pH, volume of buffer, amount of adsorbent, flow rate, preconcentration factor and effect of diverse salts and cations were studied. The optimised conditions were utilized for the determination of Cu, Fe, Ni and Zn in various water, beverage and human hair samples.

Keywords: Preconcentration 5-Br-PADAP Copper Nickel Iron Zinc Mineral water Wastewater Human hair FAAS determination

Quantitative analysis of undefined mixtures – "fishing net" algorithm by Liudmil Antonov; Vesselin Petrov (pp. 1312-1317).

An approach for quantitative analysis of mixtures with unknown individual responses of the components is discussed. Although it is based on a resolution of overlapping bands technique, the main emphasis is not given to the computational facets of curve fitting. A logical procedure is described, allowing estimation of the unknown concentrations in the mixture, and both the number of overlapping bands and their assignment to the components in the solution to be determined automatically. A general conclusion about the precision of the method cannot be defined, because it depends on the extent of overlapping of the individual spectra of the components and their complexity. Using this procedure a complicated three-component acid-base equilibrium of a halochromic dye in solution is studied.

Keywords: Overlapping bands Optical spectroscopy Quantitative analysis Curve fitting

Study of 2-(2-quinolinylazo)-5-dimethylaminobenzoic acid as a new chromogenic reagent for the spectrophotometric determination of cobalt by Zhong Li; Yang Guanyu; Baoxing Wang; Ciqing Jiang; Giayuang Yin (pp. 1318-1324).

2-(2-Quinolinylazo)-5-dimethylaminobenzoic acid (QADMAB) is proposed as a new sensitive and selective chromogenic reagent for spectrophotometric determination of cobalt. The QADMAB reacts with cobalt in the presence of cetyl trimethylammonium bromide (CTMAB) medium to form a violet complex of molar ratio 1:2 (cobalt to QADMAB) in the pH range 3.2–5.2. The molar absorptivity of the complex is 1.28×10⁵ L mol^–1 cm^–1 at 625 nm. Beer's law is obeyed in range 0.01–0.32 µg mL^–1. The relative standard deviation for eleven replicate samples of 0.2 µg mL^–1 is 0.76%. This method was applied to the determination of cobalt in biological samples, Vitamin B₁₂, alloys and water with good results.

Keywords: Cobalt Spectrophotometry 2-(2-Quinolinylazo)-5-dimethylaminobenzoic acid Biological samples Vitamin B12 Water Alloys

Spectrophotometric determination of silver with 2-(2-quinolylazo)-5-diethylaminophenol as chromogenic reagent by Guangyu Yang; Qiufen Hu; Jihong Yang; Jiayuan Yin (pp. 1325-1329).

A new chromogenic reagent, 2-(2-quinolylazo)-5-diethylaminophenol (QADEAP) was synthesized. A highly sensitive, selective and rapid method for the determination of silver based on the rapid reaction of silver(I) with QADEAP has been developed. In the presence of citric acid–sodium hydroxide buffer solution (pH=5.0) and sodium dodecyl sulfonate (SDS) medium, QADEAP reacts with silver to form a violet complex of a molar ratio 1:2 (silver to QADEAP). The molar absorptivity of the complex is 1.33×10⁵ L mol^–1 cm^–1at 590 nm. Beer' s law is obeyed in the range of 0.01–0.6 µg mL^–1. The relative standard deviations for eleven replicate samples of 0.2 µg mL^–1 is 1.38%. This method was applied to the determination of silver in water with satisfactory results.

Keywords: Silver Spectrophotometry 2-(2-Quinolylazo)-5-diethylaminophenol

Detection of zirconium in organic and aqueous phases using an inductively coupled plasma-mass spectrometer and the same aqueous standards by Christian Ekberg; Paul L. Brown; Arvid Ödegaard-Jensen; David M. Hill; Atun W. Zawadzki (pp. 1330-1334).

Solvent extraction requires measurement of both aqueous and organic phases, and common techniques of such measurements are tedious and time consuming. This paper outlines an inductively coupled plasma-mass spectrometric technique in which both aqueous and organic phases (both contained in a carrier phase, ethanol) can be measured using the same calibration curve. The method has proved to be successful as long as the organic and aqueous content in the carrier phase is kept below 10%. The developed technique is a more convenient tool for solvent extraction chemists who have often used radioactive tracers within their experimental techniques. In addition, this technique may be used in environmental studies involving the analysis of organic fractions, such as metal fingerprinting of petroleum fluids. In such analyses, the ability to use more available and traceable aqueous standards will lead to significantly improved confidence in the analytical results.

Keywords: ICP-MS measurements Organic phase concentrations Emulsions Solvent extraction Zirconium

Modification of diamond single crystals by chromium ion implantation with sacrificial layers by H.-R. Stock; J. Kohlscheen; P. Mayr (pp. 1335-1337).

Single-crystal diamond surfaces were implanted with chromium ions. Ion energies chosen were 120 and 180 keV. Ion doses of 1×10¹⁷ cm^–2 were applied at a substrate temperature of 750 °C. Reduced lattice damage could be obtained by deposition of a titanium sacrificial layer with a thickness of 10 and 50 nm before implantation. Depth profiles of the elemental binding states were taken by photoelectron spectroscopy. The effect of the sacrificial layer thickness on diamond lattice damage was investigated by infrared spectroscopy.

Keywords: Ion implantation Chromium Diamond single crystals Spectroscopy

Simultaneous determination of major, minor and trace elements in biocarbonates by inductively coupled plasma mass spectrometry by Yali Sun; Min Sun (pp. 1338-1340).

A method was developed for simultaneous determination of major (Ca), minor (Mg and Sr) and trace (Ba and U) elements in biocarbonates by inductively coupled plasma mass spectrometry (ICP–MS). The method precision (RSD%) is 0.73% for Ca, 0.77% for Mg, 0.59% for Sr, 2.02% for Ba, 1.13% for U, 0.67% for Mg/Ca, 0.27% for Sr/Ca, 2.06% for Ba/Ca and 1.23% for U/Ca. The ratio precision suggests that ICP–MS is satisfactory for obtaining multi-ratio data from biocarbonates. This technique was applied to 67 continuous coral samples.

Keywords: Major elements Minor elements Trace elements Multi-ratio Biocarbonates Inductively coupled plasma mass spectrometry

Separation and preconcentration of Se(IV)/Se(VI) species by selective adsorption onto nanometer-sized titanium dioxide and determination by graphite furnace atomic absorption spectrometry by Shunxing Li; Nansheng Deng (pp. 1341-1345).

A simple and sensitive method for the selective determination of Se(IV) and Se(VI) in natural water and sludge samples through an adsorptive process on a nanometer-sized TiO₂ (anatase) was developed. The conditions for quantitative and reproducible preconcentration, elution, and subsequent GFAAS determination were established. The proposed method gave a concentration factor of 50 for a 100 mL sample volume, characterized by high precision, high reproducibility, and direct determination of Se(IV)/Se(VI). The detection limits (3σ, n=11) were 4.7 ng L^–1 for Se(IV) and 6.3 ng L^–1 for Se (VI); the precision (relative standard deviation) was 0.7% for Se (IV) and 0.9% for Se (VI) at the 0.5 µg L^–1 level.

Keywords: Selenium Speciation Preconcentration Titanium dioxide Atomic absorption spectrometry

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Analytical and Bioanalytical Chemistry (v.374, #7-8)

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Analytical and Bioanalytical Chemistry (v.374, #7-8)