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Analytical and Bioanalytical Chemistry (v.366, #3)
Improved recovery of trace amounts of gold (III), palladium (II) and platinum (IV) from large amounts of associated base metals using anion-exchange resins by I. Matsubara; Y. Takeda; K. Ishida (pp. 213-217).
The adsorption and desorption behaviors of gold (III), palladium (II) and platinum (IV) were surveyed in column chromatographic systems consisting of one of the conventional anion-exchange resins of large ion-exchange capacity and dilute thiourea solutions. The noble metals were strongly adsorbed on the anion-exchange resins from dilute hydrochloric acid, while most base metals did not show any marked adsorbability. These facts made it possible to separate the noble metals from a large quantity of base metals such as Ag (I), Al (III), Co (II), Cu (II), ¶Fe (III), Mn (II), Ni (II), Pb (II), and Zn (II). Although it used to be very difficult to desorb the noble metals from the resins used, the difficulty was easily overcome by use of dilute thiourea solutions as an eluant. In the present study, as little as 1.00 μg of the respective noble metals was quantitatively separated and recovered from as much as ca. 10 mg of a number of metals on a small column by elution with a small amount of dilute thiourea solution. The present systems should be applicable to the separation, concentration and recovery of traces of the noble metals from a number of base metals coexisting in a more extended range of amounts and ratios.
Oxygen determination in calcium fluoride by deuteron activation analysis by Ch. S. Sastri; G. Blondiaux; P. Hoffmann; H. M. Ortner; H. Petri (pp. 218-220).
Oxygen at trace level in calcium fluoride was determined by instrumental deuteron activation analysis based on the 16O(d,n)17F reaction. The irradiations were performed with 2.5 MeV deuterons for 60 s at currents ranging from 300 to 500 nA. The results obtained for powders and single crystals were compared.
Evaluation of hydrogen line emission and argon plasma electron concentrations resulting from the gaseous sample injection involved in hydride generation-ICP-atomic emission spectrometric analysis by D. A. Batistoni; R. N. Garavaglia; R. E. Rodríguez (pp. 221-227).
The simultaneous injection of volatile hydride species and hydrogen gas, originating in reagent decomposition, was monitored during the operation of a continuous hydride generation manifold employed for the determination of trace arsenic by HG-ICP-AES. Line and background intensities as well as the FWHM of the hydrogen Hγ and Hδ lines were measured, and electron number densities (ne) estimated from Stark broadening of the line profiles. Results were compared with those obtained by conventional pneumatic injection of aqueous solutions. Overlapping with atomic nitrogen lines at 410 nm and 411 nm tends to distort the Hδ line profile for the hydrogen-seeded plasma, rendering unreliable results. The N I lines seem to be quenched by the presence of water aerosol. More consistent results were obtained with the Hγ line. When no solutions are pumped through the hydride generation manifold (“dry” plasma), the measured ne value was (1.57 ± 0.22) × 1015 cm–3. Conversely, when the reducing reagent flow was replaced by pure water (corresponding to the injection of water vapor in equilibrium that is swept by the argon carrier gas passing through the phase separator), the electron concentration is 25% higher. In that case the ne value agrees between the experimental error with that obtained for a plasma in which a water aerosol is introduced at a flow rate of 1 mL/min. An enhancement of 52% relative is observed in ne when the system is operated under optimized conditions for arsine generation, employing sodium tetrahydroborate in acidic medium as reducing agent (i.e. hydrogen seeded plasma). It was also observed that the continuum emission near 410 nm for the hydrogen containing plasma correlates with the measured electron number density, suggesting that the background enhancement under hydride generation conditions may respond to the ion-electron recombination mechanism.
Depth profiling of tin-coated glass by laser ablation inductively coupled plasma emission spectrometry with acoustic signal measurement by Viktor Kanický; Vítězslav Otruba; Jean-Michel Mermet (pp. 228-233).
A pulsed, frequency-quadrupled Nd:YAG laser (266 nm, 10 Hz) coupled to an inductively coupled plasma atomic emission spectrometer (ICP-AES) was employed for depth profiling by ablation of a pyrolytically deposited Sn layer (300 nm) on float glass. The procedure consisted of performing individual ablation cycles (layer-by-layer). A raster with stroke distance of either 50 μm or 200 μm (the raster density) was used as an ablation pattern. The ablation was stopped after each cycle and the peak area of the resulting transient optical signal of the ICP discharge was plotted against the cycle number. The ablation rate of 90 to 20 nm per cycle at a low-energy pulse (6 mJ to 1 mJ) was determined by profilometry. A beam masking was employed to attenuate the laser shot energy and to eliminate the peripheral irregularity of the beam profile. Almost uniform removal of the square area (1 mm × 1 mm) of the coating by ablation was achieved by combining the fitted raster density, beam masking, focusing and beam energy. Different ablation processes were distinguished in cases of the tin coating and the uncoated glass surface. While the coating was mainly evaporated, the uncoated glass surface exhibited a crumbling associated with production of glass powder. This was confirmed by electron microscopy observations. The measured acoustic signal followed the behavior of the emission intensity of the Sn line and was supposed to be proportional to the amount of Sn vapors. The emission intensity depth profile of the Sn coating with graded structure was obtained, which qualitatively corresponded with the depth profile measured by secondary ion mass spectrometry.
Age determination of plutonium material in nuclear forensics by thermal ionisation mass spectrometry by M. Wallenius; K. Mayer (pp. 234-238).
Age is a key parameter when deducing the history of plutonium material, i.e. the plutonium produced in the nuclear reactors. This is of vital importance, when a smuggled plutonium sample has been seized and the origin has to be determined. A methodology is described which allows accurately to determine the age of plutonium material by thermal ionisation mass spectrometry using independent parent/daughter relations. This has been demonstrated for Reference Materials of known ages as well as for real samples. The already established method using gamma spectrometry is compared to this.
Catalytic determination of ultra trace amounts of tellurium by 2.5-order differential oscillopolarography by Lijun Li; Pingang He; Yuzhi Fang (pp. 239-243).
A highly sensitive and selective catalytic method with 2.5-order differential oscillopolarographic detection is described for the determination of tellurium, based on its activation effect on the slow Pd(II)-catalyzed reaction of sodium hypophosphite and methyl red in hydrochloric acid medium at 100 °C. Methyl red exhibited a sensitive 2.5-order differential polarographic wave at –0.35 V ¶(vs. SCE) in the supporting electrolyte of pH 5.0 acetate buffer solution and was chosen as the indicating component for the indirect determination of tellurium. A calibration curve of tellurium in the range of 0.02–2.0 ng mL–1 was obtained by the fixed-time procedure. The detection limit was 0.007 ng mL–1. Possible interferences by co-existing substances were examined. The new method has been used to analyze trace tellurium in organs of white mice with satisfactory results. RSD was 0.54% to 2.10%, recovery 98.4% to 95.7%. The mechanism is also discussed.
Determination of dichloroacetic acid and trichloroacetic acid by liquid-liquid extraction and ion chromatography by Ya-Wen Ko; T. J. Gremm; G. Abbt-Braun; F. H. Frimmel; Pen-Chi Chiang (pp. 244-248).
An extraction technique using MTBE (methyl tert. butyl ether) and reagent water in combination with ion chromatography and conductivity determination was developed to quantify dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) concentrations in raw water after chlorination. The detection limit of the method was 0.45 and 1.50 μg/L for DCAA and TCAA, respectively. Mean values of recovery ranged from 90 to 96% for DCAA and 95 to 108% for TCAA. The evaluation of recovery and precision of the method indicates that the performance characteristics are comparable with gas chromatographic (GC) methods reported in literature. In addition, the procedure is simple, fast, and does not need any derivatization step. Application of the analytical method to the determination of DCAA and TCAA in real samples is shown.
Detection of bioactive surfactants in aqueous solutions on the basis of H2O2-voltammetry by T. Navrátil; L. Novotný (pp. 249-253).
The voltammetric determination of surfactants at the hanging mercury drop electrode in aqueous solutions is described, based on the shift of the peak potential ΔEP or the increase of the peak height ΔiP of the electroreduction of hydrogen peroxide or of the second oxygen reduction step, with increasing concentration of surfactants. Although the selectivity of this method is rather limited, it could be utilized, e.g., for monitoring the absence (or presence) or for the determination of the contents of specified surfactants by comparing the obtained ΔiP (ΔEP) signal with the reference state of the system or with that of ¶a selected reference surface active substance. As model surfactants n-octanol, tetrabutylammonium chloride and sodium dodecylbenzenesulfonate were used, the regular adsorption behavior of which is well known. The method was successfully applied to control the presence of a commercial detergent in water for rinsing bottles for infusion solutions.
Combination of asymmetric flow field-flow fractionation (AF4) and total-reflexion X-ray fluorescence analysis (TXRF) for determination of heavy metals associated with colloidal humic substances by A. Exner; M. Theisen; U. Panne; R. Niessner (pp. 254-259).
To assess the structural variability of colloidal humic substances and the associated heavy metals an off-line coupling of asymmetric flow field-flow fractionation (AF4) with total-reflection X-ray fluorescence analysis (TXRF) is presented. AF4 allows a rather gentle separation of colloids with a minimum of interference and artifacts as no shear forces, drying, or interactions with a stationary phase are involved. After a calibration with suitable polymer particles of known molecular weight, the molecular weight distribution of colloidal humic substances between 1 and 103 kDa can be assessed with AF4. The combination with TXRF permits a simultaneous multielement analysis after preconcentration of samples on the AF4 channel using an optimized buffer. The analysis of seepage and sewage water sample and a sewage sludge sample yielded continuous distributions of the molecular weight and the associated heavy metals. The potential of AF4-TXRF coupling for the study of metal ion exchange equilibria with colloids was demonstrated by spiking seepage water with various heavy metals and subsequent AF4-TXRF analysis of the heavy metals bound to the colloidal fraction (Cu, Cr, Zn, Ni, Co).
Calibrationless flow-through stripping coulometric determination of arsenic(III) and total arsenic in contaminated water samples after microwave assisted reduction of arsenic(V) by L’. Jurica; A. Manová; J. Dzurov; E. Beinrohr; J. A. C. Broekaert (pp. 260-266).
A simple and rapid procedure for the calibrationless determination of trace concentrations of As(III) and total As in contaminated water samples is presented. Arsenic is preconcentrated as As(III) in a flow-through cell with a gold plated porous electrode and is then stripped anodically by a constant current. The stripping chronopotentiogram is registered and evaluated. The As concentration is calculated directly from the combined Faraday’s laws. The total As content was determined after converting all As species to As(III) by microwave-assisted reduction with hydrazine hydrochloride in a closed vessel. The detection limit was found to be 0.15 μg/L and the linear response range was 0.5 to 10 000 μg/L. Tap water, surface water, and waste water samples were analyzed.
Analytical characterization of municipal solid waste incinerator fly ash by P. Fermo; F. Cariati; A. Pozzi; M. Tettamanti; E. Collina; D. Pitea (pp. 267-272).
The synergy of the micro FT-IR (Fourier Transform-Infrared) and SEM-EDX (Scanning Electron Microscopy-Energy Dispersive X-ray) techniques has been shown to be particularly helpful and effective for the characterization of inorganic compounds in fly ashes. The experimental data obtained by these techniques have been interpreted in comparison with those of other techniques. The presence of calcium carbonate, some sulfates, ammonium nitrate, calcium hydrogen phosphate, some chlorides, some oxides and aluminium silicates have been verified.
Determination of trace elements in marine plankton by inductively coupled plasma mass spectrometry (ICP-MS) by Z. Arslan; N. Ertas; J. F. Tyson; P. C. Uden; E. R. Denoyer (pp. 273-282).
A method has been developed for the determination of 23 elements in marine plankton in which inductively coupled plasma (ICP) source mass spectrometry (MS) was used to quantify the elements in the solution after digestion in a mixture of hydrofluoric and nitric acids in sealed PTFE vessels in a microwave field. The procedure was validated by the analysis of a standard reference soil (SRM 2709 San Joaquin Soil) and a standard reference fresh water plankton (CRM 414). The method was applied to the analysis of several marine plankton samples grown under controlled conditions including several whose growth media had been enriched with selenium. Matrix induced signal suppressions and instrumental drift were corrected by internal standardization. The suitabilities of germanium, indium, rhodium, scandium and yttrium as internal standard elements were evaluated. Neither scandium nor yttrium could be used due to the presence of these elements in the samples, germanium was used for the determination of As, Co, Cu, Fe, Ni, Se, Si and Zn, indium was used for Al, Ba, Ca, Eu, Sr, and Tl, and rhodium was used for Cd, Cr, Hg, Mg, Pb, Sb, Sn, and V. For Al, Ca, Cr, Cu, Fe, Mg, Mn, Ni, Si, Sr, V, and Zn internal standardization did not completely compensate for the suppressive effect of the heavier elements and the solutions were diluted. However, for As, Ba, Cd, Co, Eu, Hg, Pb, Sb, Se, Sn and Tl, it was possible to obtain accurate results despite the 35–¶40% suppression in the signals. Isobaric overlap was only a problem in the cases of 42Ca and 78Se; 44Ca and 77Se, respectively, were used. Memory effects were only observed with Hg for which a nitric acid-sodium chloride solution was the most effective wash-out solution. The marine plankton samples were able to tolerate a higher concentration of Hg as the selenium concentration increased.
Optimization of microwave-assisted extraction of hydrocarbons in marine sediments: comparison with the Soxhlet extraction method by E. Vázquez Blanco; P. López Mahía; S. Muniategui Lorenzo; D. Prada Rodríguez; E. Fernández Fernández (pp. 283-288).
Microwave energy was applied to extract polycyclic aromatic hydrocarbons (PAHs) and linear aliphatic hydrocarbons (LAHs) from marine sediments. The influence of experimental conditions, such as different extracting solvents and mixtures, microwave power, irradiation time and number of samples extracted per run has been tested using real marine sediment samples; volume of the solvent, sample quantity and matrix effects were also evaluated. The yield of extracted compounds obtained by microwave irradiation was compared with that obtained using the traditional Soxhlet extraction. The best results were achieved with a mixture of acetone and hexane ¶(1 : 1), and recoveries ranged from 92 to 106%. The extraction time is dependent on the irradiation power and the number of samples extracted per run, so when the irradiation power was set to 500 W, the extraction times varied from 6 min for 1 sample to 18 min for 8 samples. Analytical determinations were carried out by high-performance liquid chromatography (HPLC) with an ultraviolet-visible photodiode-array detector for PAHs and gas chromatography (GC) using a FID detector for LAHs. To test the accuracy of the microwave-assisted extraction (MAE) technique, optimized methodology was applied to the analysis of standard reference material (SRM 1941), obtaining acceptable results.
Collaborative study for the quality control of trace element determinations in paint coatings. Part 2. Certification of alkyd resin paint reference materials for the migratable contents of trace elements (CRMs 620 and 623) by P. Roper; R. Walker; Ph. Quevauviller (pp. 289-297).
This paper describes the preparation, homogeneity studies and certification of a series of two paint reference materials (mild steel coated with alkyd resin paint, CRM620, and comminuted paint from alkyd resin paint, CRM623) which have been produced in support of the EU Toy Safety Directive (88/378/EEC). The reference materials have been certified for levels of toxic element migration using the method specified in European Standard EN71-3:1994 published by the European Committee for Standardization. As such, the certified values, indicative values and range data quoted for the reference materials in this paper are method specific and relate only to European Standard EN71-3:1994. The paper summarizes the analytical work carried out and gives a description of the analytical methods used to measure As, Ba, Cd, Cr, Hg, Pb, Sb and Se, the 8 toxic elements specified in European Standard EN71-3:1994, in the sample extracts. Descriptions of the reference materials, certified values, indicative values together with their associated uncertainties or range of laboratory means as appropriate are given. The preparation of a (not certified) reference material (beechwood coated with nitrocellulose paint, RM621) is also described and assigned values for As, Ba, Cd and Se are given. The Hg content could not be certified in any of the reference materials, owing to a high dispersion of results.
Validated method for the determination of platinum from a liposomal source (SPI-77) in human plasma using graphite furnace Zeeman atomic absorption spectrometry by J. M. Meerum Terwogt; M. M. Tibben; H. Welbank; J. H. M. Schellens; J. H. Beijnen (pp. 298-302).
A sensitive analytical method based on flameless atomic absorption spectrometry with Zeeman correction has been validated for the quantitative determination in human plasma of platinum originating from cisplatin in a liposomal source, SPI-77. The performance of the method was acceptable over a sample concentration range of 0.125–1.25 μmol platinum/L and the lower limit of quantification was determined to be 1.25 μmol platinum/L in undiluted clinical samples. The performance data of the assay were investigated using both a calibration curve with carboplatin in plasma ultrafiltrate and diluted human plasma samples spiked with SPI-77. The recoveries, between-day and the within-day precisions of both methods of calibration were not significantly different allowing carboplatin ultrafiltrate calibration standards to be used to quantify platinum derived from SPI-77 in human plasma. Apparently, the liposomal formulation had no significant influence on the determination of platinum. The usefulness of the presented method was demonstrated in a phase I clinical and pharmacokinetic study. In addition, in vitro experiments were carried out to determine the distribution of SPI-77 in blood. The results indicated that platinum from SPI-77 mainly concentrates in plasma and that binding to and/or endocytosis in red blood cells is negligible.
Application of magdala red as a fluorescence probe in the determination of nucleic acids by H. -H. Yang; Q. -Z. Zhu; Q. -Y. Chen; D. -H. Li; J. -G. Xu (pp. 303-306).
A fluorescence quenching method was developed for the rapid determination of DNA and RNA using magdala red as fluorescence probe. In weakly acidic ¶medium, the fluorescence of magdala red (λex>lem = 54055 nm) can be largely quenched by DNA or RNA. The calibration graphs are linear over the range 0.01–¶1.2 μg/mL for both calf thymus DNA (CT DNA) and salmon DNA (SM DNA), and 0.015–1.0 μg/mL for yeast RNA, respectively. The corresponding detection limits are ¶6.0 ng/mL for CT DNA, 7.0 ng/mL for SM DNA and ¶15.0 ng/mL for yeast RNA, respectively. CT DNA could be determined in the presence of 20% (w/w) yeast RNA, and the relative standard deviation of six replicate measurements is 3.18% for 400 ng/mL of CT DNA. Interference from coexisting substances in the determination of DNA was also examined. Real samples were determined with satisfactory results.
Determination of molybdenum in the presence of 2-(2-benzothiazolylazo)-p-cresol by catalytic-adsorptive stripping voltammetry by I. C. S. Fraga; P. A. M. Farias; A. K. Ohara (pp. 307-309).
The adsorptive collection of the molybdenum (VI) complexed with 2-(2-benzothiazolylazo)-p-cresol (BTAC) coupled with the catalytic current of the adsorbed complex at a static mercury drop electrode yields an ultrasensitive voltammetric procedure for the determination of molybdenum. Optimal experimental conditions were: a stirred acetate buffer ¶0.2 M (pH 3.5) as supporting electrolyte, a BTAC concentration of 1.0 × 10–6 M as ligand, and a concentration of 0.1 M potassium nitrate as the oxidizing agent. In addition, a preconcentration potential of –0.080 V vs Ag/AgCl (3 M KCl), equilibration time of 15 s, a frequency of 30 Hz, a scan increment of 2 mV, a pulse amplitude of 0.050 mV, and a drop area of 0.032 cm2 were used. The cyclic voltammogram was recorded using a staircase wave with a scan rate of 100 mV/s. The forward scan starts at the initial potential of –0.080 V and is reversed at –0.90 V. Using the catalytic current at ∼–0.55 V the response to the Mo(VI) was found to be linear over a concentration range of 1.0–10.0 μg/L. The limit of detection is as low as 6.2 × 10–10 M with 4 min of preconcentration time. The possible interference of other trace ions was investigated. The merits of this procedure are demonstrated using of reference samples.
Generation of a methylbismuth species and its electrothermal vaporization for the determination of bismuth by inductively coupled plasma mass spectrometry by Y. Okamoto (pp. 309-311).
Inorganic bismuth(III) was converted to a methylbismuth species, possibly trimethylbismuth, by a thermochemical reaction with methyllithium. It instantly vaporized and was then introduced into the ICP ion source to detect the 209Bi signal. Utilizing an exchangeable small sample cuvette placed on the tungsten boat furnace for the reaction was very favorable from the viewpoints of easy handling, no memory effect, and maintenance of furnace conditions. In this manner, the analyte was vaporized at quite a low temperature (150 °C). The detection limit (3σ) was 0.13 pg of bismuth and the precision in relative standard deviation for 5.0 pg of bismuth was determined to be 3.8% (n = 7).
Digestion method for silver accumulated in micro-organisms by R. Joerger; T. Klaus; J. Pettersson; C. G. Granqvist (pp. 311-312).
Silver is accumulated to high concentrations in certain microbial strains. Here a bomb digestion method is proposed, using HNO3 and HCl, for the extraction and digestion of silver and silver compounds from the organic matrix. The method is applicable for the quantitative determination of silver by inductively coupled plasma atomic emission spectroscopy.
Comparison of open microwave digestion and digestion by conventional heating for the determination of Cd, Cr, Cu and Pb in algae using transverse heated electrothermal atomic absorption spectrometry by N. N. Meeravali; S. J. Kumar (pp. 313-315).
A comparison between open microwave digestion and digestion by conventional heating was carried out for the determination of Cd, Cr, Cu, and Pb in two algae matrices using transverse heated electrothermal atomic absorption spectrometry (ETAAS). A SRM GBW 08504 cabbage was also analysed. These matrices were digested with HNO3, using a quartz vessel for microwave digestion and PFA vessel for digestion by conventional heating. Cd, Cu and Cr were determined without any modifier, while magnesium nitrate and ammonium phosphate mixed modifier was used for Pb. Results obtained by both the procedures were in good agreement with each other at 95% confidence level, and for SRM GBW 08504 cabbage the values agree well with the certified values. The limits of detection obtained were 0.0004, 0.060, 0.065 and 0.054 mg/kg for Cd, Cr, Cu, and Pb, respectively, using the microwave digestion process. The RSD for Cd was 10–15% and for the other elements 5–10%.
Analysis of phytochelatins in plant matrices by pre-column derivatization, high-performance liquid chromatography and fluorescence-detection by S. Döring; S. Korhammer; M. Oetken; B. Markert (pp. 316-318).
A sensitive method for the determination of phytochelatins in plant matrices by pre-column derivatization with monobromobimane (mBrB) and high-performance liquid chromatography (HPLC) on reversed phases and fluorescence-detection has been developed and applied to cucumber sprouts (Cucumis sativus) treated with cadmium and to the water moss Fontinalis antipyretica (Cd in environmentally-relevant concentrations). Whereas phytochelatins were found in the Cd-treated sprouts, no phytochelatins were detected in Fontinalis antipyretica.
Fourier transform infrared determination of caffeine in roasted coffee samples by J. M. Garrigues; Z. Bouhsain; S. Garrigues; M. de la Guardia (pp. 319-322).
A new procedure has been developed for the FT-IR determination of caffeine in roasted coffee samples. The method involves wetting the coffee samples with a 0.25 M aqueous NH3 solution, extracting the caffeine with CHCl3, and measuring absorbance at 1659 cm–1 using a baseline established between 1900 and 830 cm–1. The procedure proposed is fast, only requiring a total extraction time of 16 min for each sample, and provides a drastic reduction of the organic solvent consumed, from the 200 mL diethyl ether and 50 mL CHCl3 required for each sample by the reference chromatographic UV-spectrometric determination to only 5 mL CHCl3. The method provides a limit of detection of the order of 3 mg L–1 caffeine and a relative standard deviation of 0.4% for 3 independent analyses of a sample containing 18.6%mg/g caffeine. The accuracy of the FT-IR procedure was evaluated from recovery experiments on spiked samples providing values from 94.4 to 100.1% and from the comparison of results found for a series of commercial samples, by both FT-IR and the official reference procedure.