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Analytical and Bioanalytical Chemistry (v.360, #2)
Interfaces for data processing in surface analysis by K. W. Brandl; G. Dreschler; H. Störi (pp. 143-147).
As computer controlled instruments for surface analysis are in common use for many years, the problem of exchangeability of analytical data has attracted interest in the surface analysis community. More and more examples for the development of standarized data formats as the VAMAS format [1] and the Standard for Chromatography Data Communication from the AIA [2] have been published. There are a few attempts to establish standardized “data dictionaries” e.g. the parameter lists describing AES and XPS spectra pusblished in Surface Science Spectra [3, 4]. If several different analysis methods (such as AES, SAM, XPS, SIMS, STM, AFM, EPMA, …) are applied to the same sample, a quite independent and open approach is needed to be able to combine data of various instruments in a common data evaluation procedure. It could be the basic concept of real mutli-method analysis. The public domain software package MAXMIND has been developed, as only a standardized data exchange and storage format based on data dictionaries can guarantee a high level of independence of proprietary measurement systems.
A new proposal for a parameter-free integration software by Bernd Spangenberg (pp. 148-151).
An algorithm is presented that has successfully been utilized in practice for several years. It improves data analysis in chromatography. The program runs in an extremely reliable way and evaluates chromatographic raw data with an acceptable error. The algorithm requires a minimum of preliminaries and integrates even unsmoothed noisy data correctly.
Some investigations on stability and precision of an HR-ICP-MS by P. Schramel; I. Wendler (pp. 152-155).
Over a period of 4 months long- and short time stability (precision) of a high resolution inductively coupled plasma mass spectrometer (HR-ICP-MS) was investigated using an ELEMENT (Finnigan MAT, Germany) instrument. By using a special torch design, significant improvements could be achieved. Without changing any electrical parameters of the mass spectrometer, the long time stability over a time period of 4 months was measured as about ± 15% for 115In for all three steps of resolution (300, 3000, 7500). The short time stability over a period of 2–8 h was measured as about ± 10% (at maximum), also nearly independent of the resolution. The main result was the near independence of the stability from the mass-spectrometer itself, but a strong dependence on the sample introduction system, the ICP-torch and the cones.
dual stage preconcentration system for flame atomic absorption spectrometry using flow injection on-line ion-exchange followed by solvent extraction by Guanhong Tao; Z. Fang (pp. 156-160).
A dual stage preconcentration system based on flow injection on-line ion-exchange and solvent-extraction has been developed for flame atomic absorption spectrometry. Lead is taken as a model trace element. A column packed with Amberlite IRC-718 cation exchanger is incorporated into the FI manifold. The analyte is retained on the column by time-based sample loading and eluted by 1 mol/L HNO3. The eluate is subsequently merged with potassium iodide and tetrabutylammonium bromide (TBABr), and isobutyl methyl ketone (IBMK). Lead is extracted on-line into IBMK as the ion-pair formed between the iodoplumbate anion and tetrabutylammonium cation. The organic phase is separated from the aqueous phase by a gravity phase separator. 50 μL of concentrate is introduced into the nebulizer-burner system of the spectrometer. An enhancement factor of 550 is achieved with a 30 mL sample consumption at a sampling frequency of 30/h. The precision (relative standard deviation) is 2.4% at 10 μg/L level and the detection limit is 0.3 μg/L (3 σ). The method was successfully applied to the determination of lead in water samples.
Use of a capacitively coupled microwave plasma (CMP) with Ar, N2 and air as working gases for atomic spectrometric elemental determinations in aqueous solutions and oils by M. Seelig; N. H. Bings; J. A. C. Broekaert (pp. 161-166).
A comparative study was performed of 600 W capacitively coupled microwave plasmas (CMP) with different plasma gases (Ar, N2 and air) and aerosol generation with the aid of a Légère pneumatic nebulizer. Detection limits with the different working gases are in the order of 15–4000 ng/mL for Fe, Cr, Zn, Mg and Ca in aqueous solutions. The influence of organic solutions on the stability of the plasma is discussed. The determination of Co, Cr, Fe, Mg and Ni in different oil samples by OES is described, using an air-CMP and pneumatic nebulization after dilution of the oils by 20% with cyclohexane. The detection limits for these elements are in the 100–400 ng/g range. Results obtained for a waste motor oil for the elements mentioned in the concentration range of 4–50 μg/g were found to be in good agreement with those obtained by ICP-OES after digestion of the oils at high pressure in PTFE vessels.
Slurry sampling electrothermal atomic absorption spectrometry for trace element analysis of high-purity tungsten trioxide by V. Krivan; A. Heger; S. Hauptkorn (pp. 167-174).
A slurry sampling ETAAS method for the determination of trace concentrations of Ca, Co, Cr, Cu, Fe, K, Mg, Na and Ni in tungsten trioxide is presented. A high background absorption appearing with large sample amounts during atomization at high temperatures was the only matrix interference observed. It could be significantly reduced by volatilization of the matrix in the pyrolysis step. Calibration curves recorded with aqueous standards could be used for calibration in all cases excluding the determination of very low analyte concentrations of Co and Fe which required the use of the standard additions method. The results obtained by this method showed an excellent agreement with those determined in digests by ETAAS. The detection limits achievable by the slurry technique were between 1 (Ca, K, Mg, Na) and 210 (Cu) ng/g. They were mostly by more than one order of magnitude better than those of the solution techniques.
Potentiometric stripping determination of heavy metals using a graphite-reinforcement carbon vibrating electrode by T. Kakizaki; Kiyoshi Hasebe (pp. 175-178).
Potentiometric stripping determination of Cd, Cu and Zn using a vibrating electrode (VE) is presented. A simple VE was constructed by using a piezoelectric bimorph oscillator and an inexpensive graphite-reinforcement carbon (GRC) rod (a mechanical pencil). Experimental results obtained with the simple VE follow the equation valid for quantitative application of potentiometric stripping analysis (PSA) in large solutions. It was found that the GRC vibrating electrode is suitable for multielement trace analysis of small samples of 0.05 mL. The relative standard deviations for divalent metals are better than 2%.
Rapid and simple chromatographic separation of V(V) and V(IV) using KH-phthalate and their determination by flame atomic absorption spectrometry by A. Gáspár; József Posta (pp. 179-183).
A method was developed for the chromatographic separation of V(V) and V(IV) based on the different sorption forces of these vanadium species in C18 columns in presence of KH-phthalate. The vanadium species were detected with a flame atomic absorption spectrometer with acetylene/N2O flame. The detection limits (3σ) of V(V) and V(IV) were 0.18 μg/mL and 0.15 μg/mL, respectively. The relative standard deviations (N = 5) are 4.2% and 3.4% for 20–20 μg/mL V(V) and V(IV), respectively. The sampling frequency is 75/h. Because of the special interaction occurring between phthalate and V(IV) on the C18 column and the acetylene/N2O flame atomic absorption detection, practically no interferences can be detected even in large inorganic matrix.
Optimization of iodine determination according to Schöniger Analytical chemistry with 1,3-dibromo-5,5-dimethylhydantoin (DBH)a Part 1, Oxygen flask combustion Part 7 [1, 2] by Manfred Hilp (pp. 184-191).
The method of iodine determination in organic compounds according to Schöniger [3, 4] was improved by using an alkaline absorption solution of DBH. In contrast to elemental bromine DBH is a stable and easy to handle crystalline compound. For the removal of the excess of DBH 5-sulfosalicylic acid (C7H6O6S × 2H2O [5965-83-3]) [5] is more suitable than formic acid [64-18-6]. Assays for the determination of 2-iodobenzoic acid in the range from 1 to 25 mg iodine are described. 32 organic iodine compounds, mostly x-ray contrast media, could be analyzed with a percentage relative standard deviation of about 0.2%.
Immunological method for the detection of nitroaromatic residues covalently bound to humic acids by Peter Pfortner; M. G. Weller; Reinhard Niessner (pp. 192-198).
The potential of the earlier reported sandwich-immunoassay principle for the detection of nitroaromatic residues bound to humic acids was examined. A synthetic conjugate derived by coupling a 2,4,6-trinitrotoluene derivative to humic acid was used as a model substance for bound nitroaromatic residues. Spectrophotometric determination gave a content of 14 ± 1.6 μmol/g TNT-derivative in the synthetic conjugate, which was used as a calibration standard. Extensive blocking optimization was necessary to establish the sandwich-immunoassay. Experiments were carried out to check the selectivity of the developed test system. Trace amounts of 2,4,6-trinitrotoluene (25 μg/L) suppressed the assay signal completely by blocking the antibody binding sites. This was a proof for the excellent selectivity of the assay. The potential of quantitative determinations was examined with dilution experiments. During assay optimization strong non-immunological interactions between various proteins and humic acids were observed. This led to a significant improvement of the original sandwich-immunoassay, where the humic acid antibody was substituted by basic proteins. More sensitive calibration curves with higher signal intensities were achieved. This new immunoassay seems to be the method of choice for further immunological investigations of bound residues.
Mercury analysis in environmental samples by EDXRF and CV-AAS by T. H. Nguyen; J. Boman; M. Leermakers; W. Baeyens (pp. 199-204).
The analysis of total Hg in various environmental matrices was investigated using energy dispersive X-ray fluorescence (EDXRF) for both powdered and digested samples and cold vapor atomic absorption (CV-AAS) for digested samples. Several microwave decomposition procedures were evaluated with respect to the determination of Hg by CV-AAS and EDXRF. The use of different acid mixtures, microwave power settings and decomposition times were compared as well as the analysis on wet and freeze-dried samples. A set of standard reference samples were used to evaluate the procedures: NBS Citrus leaves (1572), NRC Pine needles (1575), NRC Dogfish muscle tissue (DORM-2), NRC Dogfish liver tissue (DOLM-2), BCR Human hair (397), BCR Coking coal (181) and NRC Marine sediment (PACS-1). An H2SO4/HNO3/H2O2 acid mixture was found to be optimal for the complete mineralization and digestion of biological samples for Hg by CV-AAS whereas for EDXRF both the HNO3/H2O2 and H2SO4/HNO3/H2O2 acid mixture gave good results. The detection limit of EDXRF could significantly be decreased (from 0.2 μg/g to 0.058 μg/g) by performing the analysis with digested samples. A good agreement was obtained between CV-AAS and EDXRF analysis. The obtained results were also in good agreement with certified values. The methods were applied to environmental samples (coal, trees, leaves, spinach, fish, sediments) and human hair in a coal mining area and in places where they use coal for cooking in Vietnam.
Liquid-liquid extraction of mercury(II) with triphenylphosphine sulphide: Application to medicinal and environmental samples by D. C. Nambiar; N. N. Patil; V. M. Shinde (pp. 205-207).
A method is proposed for the separation and determination of mercury(II) in environmental samples after its extraction from salicylate solution using triphenylphosphine sulphide (TPPS) as an extractant. The extraction conditions are optimized and reported. The nature of the extracted species is ascertained by a plot of log of distribution ratio versus log of concentration of salicylate and TPPS.
Chromium determination in sea water by electrothermal atomic absorption spectrometry using Zeeman effect background correction and a multi-injection technique by P. Bermejo-Barrera; Jorge Moreda-Piñeiro; Antonio Moreda-Piñeiro; Adela Bermejo-Barrera (pp. 208-212).
Electrothermal atomic absorption spectrometry (ETAAS) applying a Zeeman effect background correction system (ZEBC) and a tranverse heated atomizer was used to directly determine chromium in sea water. Calcium chloride (at a concentration of 20 mg L–1) was applied as chemical modifier with optimum charring and atomization temperatures of 1600°C and 2000°C, respectively. The detection limit was 0.2 μg L–1, by injecting 20 μL aliquot of sea water sample. This detection limit could be reduced further to 0.05 μg L–1, using multiple injections (injection of five 20 μL aliquot of sea water). The accuracy of the methods developed were confirmed by analyses of different certified reference materials. Finally, interferences from major and minor components of sea water are studied.
The determination of chromium, copper and nickel in groundwater using axial plasma inductively coupled plasma atomic emission spectrometry and proportional correction matrix effect reduction by J. L. M. de Boer; Walter van Leeuwen; U. Kohlmeyer; Peter M. Breugem (pp. 213-218).
The performance of a proportional correction matrix effect reduction procedure was investigated for an axially viewed inductively coupled plasma. It was shown that the proportional correction factor (ratio of analyte matrix effect and internal standard matrix effect) was sufficiently stable over the investigated matrix element concentration ranges (0–2000 mg/L of Na and 0–400 mg/L of Ca) for the procedure to be successful. Proportional correction results in the best correction for matrix effects compared to the classical 1 : 1 intensity ratio correction procedure or the approach without any correction, as was shown in recovery experiments using analyte spiked groundwater samples. Matrix effects as high as 18% without correction were reduced to less than 4% applying proportional correction.
Efficiency of decomposition procedures for the determination of some elements in soils by atomic spectroscopic methods by J. Medved’; Vladimír Streško; Jana Kubová; Jozefa Polakovičová (pp. 219-224).
Nine decomposition procedures for soil samples, such as via acid mixtures and fusion in open systems and microwave and autoclave dissolution (in closed systems under elevated temperature and pressure) were assessed using certified soil reference materials. The determination of various elements in solutions was performed by FAAS and ICP-OES and the results were compared with certified values and with direct current arc OES analysis.
Determination of selenium in soil by hydride generation AAS by V. Kos; Marjan Veber; Vida Hudnik (pp. 225-229).
Hydride generation AAS was applied for the determination of total selenium in soil. The influence of various anions and cations present in the sample solution on the generation of selenium hydride was investigated. Special attention was paid to the wet oxidation procedure for the sample dissolution. The proposed procedure involves microwave sample preparation by using a mixture of H2O2/HNO3/H2SO4. The accuracy of the procedure was checked by the analysis of the standard reference material Buffalo River Sediment (SRM-2704, NIST). Satisfactory agreement of the results obtained with the values reported was achieved. The detection limit of the procedure was 25 ng Se/g of soil. The relative standard deviation of the measurements varied from 5.5% for SRM-2704 up to 10% for the real soil samples.
87Sr/86Sr measurements on marine sediments by inductively coupled plasma-mass spectrometry by S. Chassery; F. E. Grousset; G. Lavaux; C. R. Quétel (pp. 230-234).
The application of inductively coupled plasma-mass spectrometry (ICP-MS) is documented for the study of the strontium isotopic composition (87Sr/86Sr) in geological samples, i.e. in the marine lithic fraction of core sediments. Methods for the determination of the isotopic composition, its accuracy and precision are reported. The results obtained simultaneously on 11 samples by both ICP-MS and thermal ionization mass spectrometry (TIMS) reveal a very good correlation (r2 = 0.955).
A highly specific polyclonal antiserum to the environmental contaminant 1,1,1-trichloro-2,2-bis-(4-chlorophenyl)-ethane (p,p′-DDT) by G. Giraudi; Claudio Baggiani; Antonella Cosmaro; Emilio Santià; Adriano Vanni (pp. 235-240).
A very selective polyclonal antiserum against 1,1,1-trichloro-2,2-bis-(4-chlorophenyl)-ethane (p,p′-DDT) was obtained by a careful choice of the haptenic structure (2,2-bis(4-chlorophenyl)-ethanol hemisuccinate). This hapten was conjugated to BSA to prepare the immunogen. The effects of different types of solid phases on the equilibrium reaction between the hapten on solid phase and the polyclonal antiserum were evaluated to obtain a fine tuning of the antiserum performances in terms of specificity for p,p′-DDT and sensitivity to low levels of this pesticide. The calibration curves obtained show that it is possible to set up a sensitive assay for p,p′-DDT, employing a p,p′-dichlorodiphenylacetic acid-based solid phase, with a detection limit of 0.12 ng/mL and a working range of about 0.21–40 ng/mL. Selectivity towards several p,p′-DDT-related substances was good (o,p-DDT 17%, p,p′-DDD 1.2% o,p-DDD 6.3%, p,p′-DDE 6.7%).
Immuno-affinity columns versus conventional clean-up: a method-comparison study for the determination of zearalenone in corn by R. Schuhmacher; R. Krska; M. Grasserbauer; W. Edinger; H. Lew (pp. 241-245).
The efficiency of a modern analytical method employing immuno-affinity columns (IACs) is compared to a well established traditional technique with respect to the determination of zearalenone (ZON) in corn in the μg/kg range. Despite of a constant error of about 4 μg/kg in the examined working range of 10–200 μg/kg, analytical data obtained from the analysis of spiked and naturally contaminated samples showed good correspondence for the compared methods. The performance characteristics of immuno-affinity-chromatography as a new clean-up technique for the determination of ZON in corn is reported for the first time and compared to a conventional clean-up procedure
ETAAS determination of Cd and Pb in plants by I. Karadjova; M. Karadjov (pp. 246-251).
Simple and rapid analytical procedures for the ETAAS determination of Cd and Pb in plant (poplar, clover, plantain) leaves are described. Optimal conditions are presented for the wet digestion of plant matrices with a mixture of nitric acid and hydrogen peroxide along with optimal temperature programmes for subsequent modifier-free electrothermal determination of Cd and Pb. Slurry preparation procedures using tetramethylammonium hydroxide or a mixture of 1 mol/L HNO3 + 1.5 mol/L H2O2 are proposed as another approach for rapid and accurate routine analysis of Cd and Pb in plant leaves. It has been found that single standard addition can be used for quantitative determination in the case of wet digestion ETAAS and standard addition to each analysed matrix is recommended in the case of slurry ETAAS. For all plant leaves investigated good agreement was achieved between the concentrations determined by wet digestion ETAAS and slurry ETAAS. The wet digestion method provides relative standard deviations for Cd ranging from 3% to 17% and for Pb from 2% to 16%. For the slurry method the RSD values are in the range of 4–31% for Cd and 4–30% for Pb, depending for both cases on the magnitude of the measured concentrations. Validity and versatility of the methods are verified by the analyses of standard reference materials.
Gas-chromatographic determination of deltamethrin in crops by Sandro Navickiene; Marta H. Kato; Luciana Polese; E. V. Minelli; Maria L. Ribeiro (pp. 252-255).
A rapid and economical method is described for the determination of deltamethrin in wheat, rice, peanuts and corn. It is based on simultaneous extraction and clean-up on a column packed with alumina and silica gel using n-hexane-ethyl ether (8:2, v/v), followed by a derivatization step and gas-chromatographic analysis. Recoveries from fortified cereal and peanut samples were determined at four concentration levels and ranged from 73 to 109%. The detection limits were 0.01 to 0.03 mg/ kg. This method simplifies the traditional procedures in terms of sample size, solvent consumption and analysis time.
Substrate inhibition in an enzymatic ordered bireactant system: non-linear modelling of the kinetics of hypoxanthine-guanine-phosphoribosyltransferase by Barbara M. Praest; Helmut Greiling; Rüdiger Kock (pp. 256-259).
Hypoxanthine-guanine-phosphoribosyltransferase (HGPRT; EC 2.4.2.8) was determined as an enzyme following an ordered bireaction in the presence of substrate inhibition due to hypoxanthine. This kind of inhibition has not been postulated for HGPRT so far. The mechanism and the kinetic constants of the reaction of HGPRT from Saccharomyces cerevisiae were investigated by initial velocity studies involving a non-linear regression analysis. In addition, two kinds of experimental designs were compared: the variation of hypoxanthine concentrations over wide ranges at different of fixed levels of 5-phosphoribosyl-1-pyrophosphate, and the use of five appropriate sets of experimental conditions each characterized by different hypoxanthine and 5-phosphoribosyl-1-pyrophosphate concentrations. Both experimental designs were consistent with an ordered bi bi mechanism including a dead-end-complex between the enzyme and hypoxanthine.
A simple procedure for the chromatographic analysis of nanoliter samples by Rosanna Toniolo; Alan Valentino; G. Bontempelli; Gilberto Schiavon (pp. 260-262).
A simple method for the analysis of nanoliter droplets is proposed, which is profitable when larger samples cannot be collected as, for instance, in the case of several biological fluids and particularly in clinical chemistry. A glass capillary associated to a micromanipulator is used to collect submicroliter volumes which are partially transferred into transparent polymeric tubings with known internal diameters (120–178 μm), where the volumes sampled are measured by meniscus collimations with a collimator microscope at suitable magnification. Both ends of these tubings are preliminarily equipped with ferrules and fittings, so as to make them suitable for connection as the loop to a conventional high-pressure injection valve. The reliability of this procedure has been tested for the analysis of Na+, K+ and Ca2+ present in minute synthetic standard samples (10–200 nL) by a conventional ion-chromatographic instrumentation. Relative standard deviations in peak area measurements (5–6%) are discussed in terms of the whole approximation affecting volume measurements, which depends on both the inconstancy of the inner diameter of the polymeric tubings employed and the uncertainty characterizing meniscus collimations. The proposed procedure can be easily extended to the determination of any organic or inorganic species present in very small samples, provided that their detection can be achieved by any chromatographic approach or, more generally, by flow injection analysis.
Copper interference on the spectrophotometric determination of iron and their simultaneous determination using bathophenantroline-disulfonic acid disodium salt by B. Baraj; J. L. Cortina; A. Sastre; M. Granados (pp. 263-265).
The interference of copper on the spectrophotometric determination of iron with bathophenantroline-disulfonic acid disodium salt was studied using an experimental design. Copper interferes even below pH 5 [1], forming a yellow complex with bathophenantroline which turned to green after 5 min. This complex showed a maximum at 425 nm with a molar absorptivity of 7.5 × 103 L mol–1 cm–1. Microgram quantities of iron and copper were determined simultaneously in water standard samples using bathophenantroline-disulfonic acid disodium salt at pH 4.8 and measuring the absorbances at two wavelengths. The interference of iron on the copper determination was also estimated. The RSDs of the method for both Cu and Fe were below 1.7%. Recoveries for Cu and Fe were within the ranges 97.2% to 98% and 99.7 to 100.5%, respectively. The method was applied to the determination of copper and iron in the waste water from a water treatment plant. The results obtained by spectrophotometry were compared with those obtained by flame AAS.
Liquid – liquid extraction behavior of V(IV) using phosphinic acids as extractants by A. Saily; S. N. Tandon (pp. 266-270).
The extraction behavior of V(IV) in the presence of Mo(VI), W(VI), U(VI), V(V), Ti(IV), Al(III), Cr(III), Fe(III), Mn(II), Zn(II) and Pb(II) has been studied using two alkylphosphinic acid extractants, Cyanex 272 and 301. The effect of various parameters, such as the nature of diluent, the type of mineral acid and the concentration of the acid, and metal ions has been investigated. The loading and recycling capacity of the extractants has been assessed. Based on the distribution data some binary separations from V(IV) were achieved.
Determination of antimony in rain water at the nanogram level with surfactant and brilliant green by A. N. Tripathi; K. S. Patel (pp. 270-272).
A new, simple, selective and sensitive method for the spectrophotometric determination of antimony in rain water is described. It includes preconcentrating Sb with surfactants (i.e. cetylpyridinium chloride (CPC) and Triton X-100 (TX-100)) into toluene and allowing the extract to react with a dye, i.e. brilliant green (BG). The value of apparent molar absorptivity is 5.55 × 105 L-mol–1· cm–1 at λmax = 620 nm; the detection limit is 3 ng/mL Sb in rain water at 3-fold preconcentration.
Flow-injection analysis based on a membrane separation module and a bulk acoustic wave impedance sensor – determination of the volatile acidity of fermentation products by Xiaoli Su; Lihua Nie; S. Yao (pp. 272-274).
A novel flow-injection analysis (FIA) system has been developed for the rapid determination of the volatile acidity of some fermentation products like vinegars and juices. The proposed method is based on the diffusion of volatile acids, mainly acetic acid, across a PTFE gas-permeable membrane from an acid stream into an alkaline stream, and the acids trapped in the acceptor solution are determined online by a bulk acoustic wave impedance sensor based on changes in the conductivity of the solution. It exhibited a linear frequency response up to 10 mmol · L–1 acetic acid with a detection limit of 50 μmol · L–1, and the precision was better than 1% (RSD) at a through-put of 72 h–1. The effects of operating voltage for the detector, cell constant of the electrode, composition of acceptor stream, flow rates and temperature on the FIA performance were also investigated.