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Analytical and Bioanalytical Chemistry (v.357, #1)
Electrothermal atomic absorption spectrometry in the study of metal ion speciation by A. K. Das; Ruma Chakraborty (pp. 1-17).
The literature on the use of electrothermal atomic absorption spectrometry (ETAAS) in the determination of metals in speciation studies of different samples is comprehensively reviewed. The methods of extraction, preconcentration, etc. in connection with speciation studies have been highlighted. The ETAAS programmes and other details of the developed methodologies are discussed. On critical examination it becomes obvious that chromium is the metal which has been analysed by most workers. Study of other metals falls in the following order: Pb, Sn, Cu, As, Al, Cd, Zn, Fe, Ni and Se. It is clearly evident that the major work on metal ion speciation has been carried out in natural water, followed by biological materials. There are also many reports on the speciation analysis of soil and sediment. Only a few papers have been published on metal speciation in airborne particulates. The analytical details of the developed methodologies have been examined in terms of limit of detection, precision and accuracy.
Effect of Ar/H2 and Kr/H2 mixtures as discharge gas on the ion intensity in dc glow discharge mass spectrometry by Morimasa Saito (pp. 18-21).
In dc glow discharge mass spectrometry, the addition of small amounts of H2 to pure Ar as discharge gas has greatly increased the ion intensities of elements compared with the conventional method using pure Ar. This phenomenon was also observed for the addition of H2 to pure Kr. The reason for the increase of the ion intensities of elements was studied by using a Kr gas mixture containing 0.2% (v/v) H2. The ion intensities of the elements P, Se and As (whose first ionization potentials are higher than the energy levels of the excited state of Kr) did not increase even if the Kr/H2 gas mixture was used. The results show that the addition of H2 significantly contributed to increasing the number of metastable argon or krypton atoms (Penning ionization).
Influence of heated spray chamber desolvation on the detectability in inductively coupled plasma atomic emission spectrometry by W. Schrön; U. Müller (pp. 22-26).
A comparison study has been made of the performance of a heated spray chamber desolvation system for sample introduction into inductively coupled plasma. The heated spray chamber system Mistral replaces the normal spray chamber of an ICP-spectrometer and improves the efficiency of both aerosol generation and transport to the plasma [1]. 27 elements in 6 sample solutions with different mineralization were measured with and without the heated spray chamber system. The higher the mineralization of the sample solution, the less was the increase of the intensity of the spectral lines of the elements determined. An increase of the intensity by the same factor for most of the elements was observed in different sample solutions like drinking water (factor 6), fresh water (factor 5), sea water (factor 1.5) and acid solutions resulting from the digestions of soil (factor 3–4) and rock (factor 2) samples. A few elements in drinking and fresh water were only detectable by using Mistral. A clear improvement of the detection limits was found, but compared to the increase of the intensity not for all elements by the same factor. The detection limits for water samples are in the lower μg/L- and the higher ng/L-level by using Mistral. So the Mistral is an alternative to the ultrasonic nebulizer.
Fullerene/liquid crystal mixtures as QMB- and SAW-coatings – detection of diesel- and solvent-vapours by F. L. Dickert; Matthias E. Zenkel; Wolf-Eckehard Bulst; Gerhard Fischerauer; Ulrich Knauer (pp. 27-31).
The detection of diesel fuel and different solvent vapours in air is described. Due to the very low vapour pressure of diesel fuel, highly mass sensitive quartz microbalance (QMB) and surface acoustic wave (SAW) sensors are used. Micro porous coatings are presented consisting of liquid crystals and buckminster fullerenes. Thereby the globular compound disturbs the structure of the rod-like component and cavities and channels are created. With these mixtures it is possible to attain a resolution of 0.5% of the vapour pressure of diesel in air with the QMB; an even fivefold increase of sensitivity can be obtained with highly sensitive SAW devices operating at 433 MHz. In the latter case alkylsilane monolayers are used to promote adhesion, which themselves show a similar sensitivity as the QMB, but with an instantaneous response.
Charged native β-cyclodextrin as a pseudostationary phase in electrokinetic chromatography by K. Bächmann; A. Bazzanella; I. Haag; K.-Y. Han (pp. 32-36).
Native β-cyclodextrin, deprotonated at its secondary hydroxyl groups has been studied as pseudostationary phase for electrokinetic chromatographic separation of highly hydrophobic compounds. Using this pseudostationary phase the separation of five polycyclic aromatic hydrocarbons (PAHs) is shown. The influence of the main parameters (field strength, pH, concentration of cyclodextrin, urea and organic solvent) on the separation of PAHs and migration behaviour of β-CD is discussed.
Effect of the concentrations of triphenyltin chloride and anion exchanger on the anion selectivity of a plasticized PVC membrane electrode by Sadayuki Koizumi; T. Imato; Nobuhiko Ishibashi (pp. 37-43).
Potentiometric selectivities of a plasticized poly(vinyl chloride) (PVC) membrane containing a hydrophobic quaternary ammonium salt and triphenyltin chloride (TPTCl) for several inorganic anions were evaluated by measurements of the membrane potential of a bi-ionic system (the so-called bi-ionic membrane potential). The addition of TPTCl to the plasticized PVC membrane containing a quaternary ammonium salt gave rise to selectivity patterns different from the Hofmeister anion series, which is observed for a membrane containing only the quaternary ammonium salt. The change in the selectivity pattern from the Hofmeister to the non-Hofmeister was observed under conditions where the TPTCl concentration was higher than the quaternary ammonium salt in the membrane. Response mechanisms and the selectivity of the TPTCl-based electrode are discussed with respect to the concentration dependence of TPTCl and quaternary ammonium salt in the membrane.
Solid-phase spectrophotometric microdetermination of iron with ascorbic acid and ferrozine by M. L. Fernández-de Córdova; A. Ruíz-Medina; A. Molina-Díaz (pp. 44-49).
A very sensitive and selective method for the determination of trace amounts of iron has been developed, based on the reduction of Fe(III) to Fe(II) by ascorbic acid, followed by chromogenic chelation of Fe(II) with ferrozine. The complex Fe(II)-ferrozine is easily sorbed on a dextran-type anion-exchange gel packed in a 1 mm cell, and the absorbance of the gel is measured directly at 569 and 800 nm. The extended linear range of the determination is 0.5–10 ng ml-1 of iron (apparent molar absorptivity=4.4×107 l mol-1 cm-1) and the precision (RSD) 1.3% for a concentration of 5 ng ml-1 of iron (n=10). The detection limit for a sample volume of 1000 ml, using 0.040 g of anion-exchanger, corresponds to 0.12 ng ml-1. The method has been successfully applied to the determination of iron in natural and waste waters, wine, soil extract and previously digested vegetal tissues, drugs and human hair.
Combination of solid phase extraction and flame atomic absorption spectrometry for differentiated analysis of labile iron (II) and iron (III) species by Abu Bakar Tawali; G. Schwedt (pp. 50-55).
The labile iron(II) and iron(III) species are complexed directly in the sample solution with 1,10 phenanthroline and ferron (8-hydroxy-7-iodoquinoline-5-sulfonic acid), respectively. The complexes thus formed are mutually adsorbed and separated by solid phase extraction. The direct determination of iron(III) and iron(II) species with flame atomic absorption spectrometry (FAAS) follows the elution of the iron(III)-ferron complex adsorbed by an anion-exchange and an iron(II)-phenanthroline complex adsorbed by a non-polar RP-18 phase. In the case of indirect determination, the iron(II)-phenanthroline complex that passes through the anion-exchange phase, is measured, and the content of iron(III) is calculated by the difference of the iron(II) and the total iron content. A direct determination with this method has been applied to the iron species analysis in wine samples and the results are compared with those obtained for the determination with adsorptive stripping voltammetry (ASV) as reference method.
Cyclic voltammetric studies of certain industrially potential iron chelate catalysts by P. S. Verma; R. C. Saxena; A. Jayaraman (pp. 56-60).
Cyclic voltammetry of iron-EDTA and iron-DETPA, in different supporting electrolytes showed electrochemical reversibility in ammonium citrate at pH 8.0, while quasi-reversible nature was noticed with iron-NTA. The absence of electroactive peaks when adding a polyhydric alcohol such as mannitol (providing greater stability to the chelate in alkaline pH) or a tertiary amine such as triethanolamine (as an organic buffer) to the supporting electrolyte enabled the use of CV for quantitative analysis of iron in a complex matrix containing these ingredients. The decrease in the diffusion coefficient of Fe(III)-chelate with an increase in the organic buffer suggested the need for limiting the concentration of the amine in order to obtain efficient mass transport while providing better pH control, when such a solution is required for the oxidation of the sulfide/hydrosulfide ion to elemental sulfur.
Separation and determination of cadmium and zinc as their thenoyltrifluoroacetone complexes with dibenzo-18-crown-6 by means of synergistic extraction and atomic absorption spectrometry by M. Billah; T. Honjo (pp. 61-64).
A new method for the separation and determination of trace amounts of cadmium and zinc in water as their thenoyltrifluoroacetone (TTA) complexes with dibenzo-18-crown-6 (DB18C6) in o-dichlorobenzene has been established by means of synergistic extraction and back-extraction combined with atomic absorption spectrometry. The effect of various factors (synergism with TTA and DB18C6, shaking time, composition of the extracted species, and mutual separation etc.) on the extraction and back-extraction of cadmium and zinc has been in- vestigated. When the mixtures were extracted for 4 min at pH 4.9, only zinc was extracted quantitatively, whereas cadmium remained in the aqueous phase. After the phases were separated, cadmium was again extracted quantitatively at pH 7.5. Then, the two phases were each shaken with 0.05–0.1 mol/l HCl in order to back-extract cadmium and zinc from the organic phases; the ions were determined individually by atomic absorption spectrometry. In the process cadmium and zinc TTA chelates in o-dichlorobenzene form stable adducts with DB18C6 (Cd(TTA)2 ⋅ nDB18C6 and Zn(TTA)2 ⋅ nDB18C6, n=0∼2). The stability constants (βn) of the adducts determined by means of the curve fitting method were log β1=4.62 and log β2=6.74 for cadmium, and log β1=3.48 and log β2=5.18 for zinc.
Preparation and characterization of chelating resins loaded with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol for preconcentration of rare earth elements by Adriana N. Masi; R. A. Olsina (pp. 65-68).
Chelating resins prepared by sorption of 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol (5-BrPADAP) on macroporous resins (Amberlite XAD-4 and XAD-7) were characterized. The adsorption properties (amount of chelating agent adsorbed per gram of resin, sorption kinetics, retention capacity, etc.) and the thermodynamic quantities of each adsorption process were determined. The retention of some rare earth elements (e.g. Er, Yb and Lu) on these chelating resins was studied in order to preconcentrate them for their determination by X-Ray fluorescence spectrometry.
Titrimetric determination of the stoichiometric composition of ceramic high-temperature superconducting materials by I. Vogel; R. Kucharkowski; G. Krabbes (pp. 69-73).
To characterize the real stoichiometry of ceramic high-temperature superconductors of the Y-Ba-Cu-O type and the Bi(Pb)-Ca-Sr-Cu-O type complex, chemical methods including digestion, separation and subsequent titrimetric determination of the elemental components were investigated. Using optimized automatic titration procedures with photometric, potentiometric or voltametric equivalence point detection, a high accuracy of the analytical results could be achieved. The random as well as the systematic errors are less than 0.5%. The exact stoichiometric coefficients of the components and thereby the phase compositions or the single phase character of the materials were determined and compared with the results of X-ray diffraction measurements.
Bromide/bromate speciation by NTI-IDMS and ICP-MS coupled with ion exchange chromatography by J. Diemer; K. G. Heumann (pp. 74-79).
Two different mass spectrometric methods, negative thermal ionization isotope dilution mass spectrometry (NTI-IDMS) and inductively coupled plasma mass spectrometry (ICP-MS), off-line and on-line coupled with anion exchange chromatography, have been developed for simultaneous bromide and bromate determinations in water samples. The detection limits of these methods are in the range of 0.03–0.09 μg/L using a 50 mL sample.The results are independent of the content of other anions, which could be demonstrated by the analyses of six mineral waters containing chloride and sulfate of up to 160 mg/L and 1500 mg/L, respectively. Bromide has been analyzed by the NTI-IDMS method in the range of 10–500 μg/L and bromate in the range of 1–50 μg/L with relative standard deviations of 0.3–1.2% and 0.4–6%. Quantification for the ICP-MS method was carried out by the standard addition technique, which resulted in relative standard deviations of 5.5% for bromide at the 500 μg/L level and of 13% for bromate at the level of about 3 μg/L. These results are compared with those described in the literature for ion chromatographic (IC) and other methods and those obtained in this work by IC using UV detection, which allows high concentrations of chloride in the bromate fraction. The detection limits of this IC method are 6 μg/L for bromide and 30 μg/L for bromate. NTI-IDMS and ICP-MS therefore fit the recommendations of the European Union (detection limit<2.5 μg/L; precision and accuracy better than 25% at the 10 μg/L level) for methods analyzing the carcinogenic bromate much better than IC and other methods applied up to now. As a definitive but time consuming method, NTI-IDMS is preferably applicable as a calibration technique, whereas ICP-MS, with relatively short analysis times, due to on-line coupling with chromatography, can be used as a sensitive and powerful routine method for trace bromide and bromate species in water samples.
Kinetic determination of carminic acid by its inhibition of lanthanide-sensitized luminescence by S. Panadero; A. Gómez-Hens; D. Pérez-Bendito (pp. 80-83).
The stopped-flow mixing technique was used to develop a simple and fast kinetic method for the determination of carminic acid based on its inhibitory effect on the fluorescence intensity of the europium(III)- diphacinone-ammonia system in the presence of Triton X-100. Analytical data can be obtained within 10 s after the reactants are mixed, which minimizes manipulation and enables the ready application of the proposed method to routine analyses for carminic acid in orange soft drinks. The dynamic range of the calibration graph was 0.5–15 μg ml-1 and the relative standard deviation less than 4%. The analytical recoveries obtained by applying the method directly to the analysis of samples ranged from 90.0 to 111.8%.
Flow injection analysis of ascorbic acid at a methylene green chemically modified electrode by A.-M. Yu; Chun-Xiang He; J. Zhou; H.-Y. Chen (pp. 84-85).
In flow injection analysis (FIA) of ascorbic acid, methylene green (MG) modified carbon paste electrodes showed high catalytic activity and stability, reducing the oxidation overpotential by 400 mV. The linear response range was over 3 orders of magnitude and the detection limit was 1×10-8 mol/L eq. 0.25 pmol with S/N=3. The influence of various experimental conditions was explored for optimum analytical performance.
Application of multivariate calibration to the simultaneous routine determination of ethanol, glycerol, fructose, glucose and total residual sugars in botrytized-grape sweet wines by means of near-infrared reflectance spectroscopy by C. M. Garcia-Jares; B. Médina (pp. 86-91).
The simultaneous determination of ethanol, glycerol, fructose, glucose and residual sugars in botrytized-grape sweet white wines was performed by means of near-infrared reflectance using 19 interference filters and a partial least squares (PLS) model in latent variables as a multivariate calibration technique. The results were compared with those obtained using other multivariate calibration techniques, such as MLR, SWR and PCR, by means of a validation set of samples with known compositions. Ethanol, fructose and residual sugars were well predicted by all the multivariate techniques. Glycerol and glucose showed the highest prediction residuals. The technique may be of practical interest in the routine analysis of these types of wines with low cost in terms of samples, time and personnel.
Determination of antimony in wine by hydride generation graphite furnace atomic absorption spectrometry by Anne-Marie Wifladt; Grethe Wibetoe; W. Lund (pp. 92-96).
A method was developed for the determination of Sb in wine by electrothermal atomic absorption spectrometry, based on preconcentration by hydride generation with collection directly in the graphite furnace. Thiourea was added for prereduction of Sb(V) to Sb(III). The hydride was directly generated from diluted wine. Palladium was used as modifier in the collection step; the overall efficiency of the hydride/trapping system was found to be 67%. Sb was determined in several samples of red wine; the concentrations found were in the range 0.6 to 5.7 μg/L Sb. The detection limit of the method was 39 pg Sb, corresponding to 0.13 μg/L Sb in wine when 0.3 mL wine was analyzed.
Thermal analysis of food carbohydrates by determination of starch gelatinization phenomena by Rita Acquistucci; R. Bucci; Andrea D. Magri; Antonio L. Magri (pp. 97-100).
A calorimetric (DSC) method for the analysis of starches and food-related compounds, based on the determination of onset and peak temperature (To, Tp) and the apparent enthalpy change (ΔH) of the starch gelatinization process is described. To set up the best experimental conditions to apply, the parameters that could affect the calorimetric response, such as temperature range of thermal analysis, water/starch ratio in the mixture, heating rate, size and weight of sample, time-temperature condition, were investigated. The method was applied to characterise starches, semolina and alimentary pasta.
Sensitive HPLC-fluorometric and HPLC-MS determination of diarrhetic shellfish poisoning (SP)-toxins as 4-bromomethyl-7-methoxycoumarin esters by Jin-Lin Shen; Christian Hummert; B. Luckas (pp. 101-104).
Extracts containing the diarrhetic shellfish poisoning (DSP) toxins okadaic acid (OA), dinophysistoxin-2 (DTX2), and dinophysistoxin-1 (DTX1) were purified on a silica gel cartridge and derivatized with 4-bromomethyl-7 methoxycoumarin (BrMmc). After pre-column derivatization the BrMmc derivatives of the DSP toxins were directly injected into an HPLC system, isocratically eluted, and quantified by fluorescence detection. The signals of the esters showed good linearity in the fluorescence detector within the examined contamination range of 0.03 mg DSP/kg to 2.5 mg DSP/kg. The detection limits for the DSP toxins as 7-Mmc esters were 0.04 ng (corresponding to 0.05 mg DSP/kg). The chromatographic conditions allow to couple the HPLC device with mass spectrometry. The method was tested with various mussel tissue samples.
Analytical characterization of manganese in rainwater and snow samples by F. Deutsch; P. Hoffmann; H. M. Ortner (pp. 105-111).
Seven rain and 2 snow samples collected in October and November 1993 were analyzed by GFAAS. Manganese concentrations ranging from 0.3 to 11.3 μg/L were found. pH-values (4.04–4.89, mean 4.52) and redox potentials (528–665 mV, mean 581 mV) were additionally determined. This is important with respect to a qualified specification of Mn in atmospheric samples. A 0.45 μm-filtration of the samples prior to GFAAS-analysis showed the same manganese concentrations in the filtrate as in the unfiltered samples. Hence, the amount of solid Mn species in the investigated samples is negligible. For an examination of the oxidation state of Mn some investigations concerning the stability of Mn(III) were carried out. They indicated that Mn(III) is unstable under atmospheric conditions. For checking whether all the manganese in rainwater exists as Mn(II), a sensitive IC method for the detection of Mn(II) was developed. By adapting a photometric procedure based on the oxidation of Leucomalachite Green (LMG) to Malachite Green (MG) by permanganate (MnO- 4) to the IC-flow-through-system, a limit of determination of 1 μg/L Mn(II) could be achieved. A comparison of the IC measurements with GFAAS-results of the filtered samples showed agreeing results. Thus, manganese in rainwater and snow exists entirely as soluble Mn(II).
Determination of selenium in seawater by Zeeman GFAAS using nickel plus NH4NO3 modifier by Liang Yan-zhong; Li Mei; Rao Zhu (pp. 112-116).
The effectiveness of nickel plus NH4NO3 as a chemical modifier for the determination of selenium in seawater by Zeeman electrothermal atomic absorption spectrometry has been evaluated. The effect of changing the modifier mass and pyrolysis hold time on the integrated absorbance of selenium and the background absorbance has been investigated. Nickel and NH4NO3 allow the quantitative stabilization of selenium in the seawater matrix up to 1300° C as compared with 600° C without modifier. The modifier further reduces the background absorbance caused by seawater. The tolerable amounts of various inteferences such as chloride, sulphate and phosphorus in the presence of nickel plus NH4NO3 are evaluated for the determination of selenium in seawater.
Long-term sampling system for the measurement of ambient air concentrations of mercury at a contaminated site by G. Dörr; D. Deinzer (pp. 117-120).
Iodized activated carbon was used as sampling medium for mercury species in ambient air. It showed satisfactory recovery in laboratory adsorption experiments with spiked air. Also, field measurements parallel to a gold trap system were conducted. After optimizing the volume flow, the results of an intermittently sampling gold collector and the continuously sampling iodized activated carbon trap agreed well. Iodized activated carbon is therefore a low cost alternative for the determination of ambient air levels of mercury. Because of the higher loading capacity of the iodized activated carbon compared with gold, it is especially suited for long-term sampling and mean-level assessment.
Analysis of aminobenzoic acids in waste water from a former ammunition plant with HPLC and combined diode array and fluorescence detection by T. C. Schmidt; M. Petersmann; L. Kaminski; E. von Löw; G. Stork (pp. 121-126).
Aminobenzoic acids are of major interest in clinical analysis, but their determination in environmental samples has been rarely done. Therefore a method for the determination of 10 aminobenzoic acids in water has been developed, using high-performance liquid chromatography with combined diode array and fluorescence detection. A separation of the analytes has been achieved with a buffer pH 3/methanol gradient. The general elution order has been m-substituted
Determination of hemoglobin in plasma and serum by linear-sweep polarography by Jun-feng Song; Xiao-feng Kang; Wei Guo (pp. 127-129).
A new method for the determination of hemoglobin (Hb) is described. It is based on the amplification of the Hb enzyme-catalyzed reaction between O-phenyldiamine (OPD) and H2O2 and polarographic measurement of the enzyme-generated product 2,2′-diaminoazobenzene (DAA). A linear calibration plot has been obtained within the range of 1∼20 μg/ml (r = 0.987) Hb. The assay is performed on the microtitre plate to avoid the influence of serum protein and to obtain good reproducibility. The method is practical, reliable and convenient, and has been applied to determine Hb in plasma and serum.
Capillary electrochromatographic separation of amino acid enantiomers with molecularly imprinted polymers as chiral recognition agents by J.-M. Lin; Tatsuro Nakagama; Xing-Zheng Wu; Katsumi Uchiyama; Toshiyuki Hobo (pp. 130-132).
The use of molecularly imprinted polymers polymerized in a capillary for the separation of amino acid enantiomers by electrochromatography is described. The substrate-selective polymers were prepared by using l-phenylalanine anilide as print molecule and methacrylic acid as the functional monomer. The treatment of the inside surface of the capillary, the composition of the polymer and the electrochromatographic running conditions were investigated. This preliminary report demonstrated a novel and simple method for capillary electrochromatographic separations of amino acid enantiomers using molecularly imprinted polymers.