Jerzy Mierzwa

New method of gold-film electrode preparation for anodic stripping voltammetric determination of arsenic (III and V) in seawater

A new method of efficient rotating gold-film glassy-carbon electrode preparation prior to the determination of As(III) and As(V) in seawater by anodic stripping voltammetry (ASV) is described. Factors affecting sensitivity and precision including pH, deposition time and potential, rotation and scan rate, and the nature of working electrode were investigated. Electroinactive As(V) was reduced to As(III) by gaseous SO(2) prior to ASV determination. For a deposition time of 4 min the determination limit was approximately 0.19 ppb. Precision of the proposed method was very good (RSD=2-0.6% at 1-5 ppb) and a relatively good accuracy determined by analysis of certified reference seawater (CASS-1) and seawater samples spiked with an arsenic standard solution, was also obtained.

Comparative determination of Ba, Cu, Fe, Pb and Zn in tea leaves by slurry sampling electrothermal atomic absorption and liquid sampling inductively coupled plasma atomic emission spectrometry

The comparative determination of barium, copper, iron, lead and zinc in tea leaf samples by two atomic spectrometric techniques is reported. At first, slurry sampling electrothermal atomization atomic absorption spectrometry (ETAAS) was applied. The results of Ba and Pb determination were calculated using the method of standard additions, and results of Cu, Fe and Zn from the calibration graphs based on aqueous standards. These results were compared with the results obtained after microwave-assisted wet (nitric+hydrochloric+hydrofluoric acids) digestion in closed vessels followed by inductively coupled plasma-atomic emission spectrometric (ICP-AES) determination with the calibration by means of aqueous standards. The exception was lead determined after a wet digestion procedure by ETAAS. The accuracy of the studied methods was checked by the use of the certified reference material Tea GBW-07605. The recoveries of the analytes varied in the range from 91 to 99% for slurry sampling ETAAS, and from 92.5 to 102% for liquid sampling ICP-AES. The advantages of slurry sampling ETAAS method are simplicity of sample preparation and very good sensitivity. Slurry sampling ETAAS method is relatively fast but if several elements must be determined in one sample, the time of the whole microwave-assisted digestion procedure and ICP-AES determination will be shorter. However, worse detection limits of ICP-AES must also be taken into the consideration in a case of some analytes.

Determination of chromium, manganese and vanadium in sediments and soils by modifier—free slurry sampling electrothermal atomic absorption spectrometry

Abstract Slurried sediment and soil samples of the certified reference materials with a highly elevated level of the metals of interest (Mn, Cr and V) were analysed by electrothermal atomic absorption spectrometry (ETAAS) with Zeeman effect background correction. The method of slurry preparation and time-temperature programmes were optimized and, finally, the use of chemical modifiers was not necessary. The effect of alternate spectral lines and gas mini-flows on characteristic masses of analytes was studied. The homogeneity of samples and the influence of short sample grinding were also discussed. The simple, aqueous standard based calibration graphs (except Mn at the concentration > 1000 mg kg −1 ) were applied for the quantification of results. The results of determinations obtained by slurry sampling agreed well with the cetified values, and the relative standard deviations (RSDs) for the over-all analytical procedure repeatability (at slurries concentration level about 2 mg/2 ml) were less than 9.5%, except manganese (10.4%).

Slurry sampling hydride generation atomic absorption spectrometry for the determination of extractable/soluble As in sediment samples

Abstract A method combining the sampling of slurry pretreated by ultrasonic agitation and microwave assisted extraction with hydride generation atomic absorption spectrometry (HGAAS) for the determination of arsenic in sediment samples is proposed and evaluated. The pretreatment of slurried samples by ultrasonication enabled the extraction of (approximately) up to 85% of arsenic from the studied sediment samples. The further (slight) improvement of the efficiency of extraction was accomplished by the introduction of a short microwave-accelerated treatment. l -cysteine was used as an efficient pre-reduction reagent. The accuracy and precision of the slurry sampling HGAAS method were studied using the certified reference materials: Sediment GBW 30043 (NRCCRM, Peoples Republic of China), Sediment NIST 2704 (NIST, USA) and Marine Sediment BCSS-1 (NRCC, Canada). The relative standard deviation of the full (overall) analytical procedure was 8.5% and an absolute limit of detection of 2.75 ng was achieved. Factors which influence the reliability of this method are, for example, the choice of slurry liquid phase (extraction medium), sample homogeneity and, in particular, very effective mixing of slurries.

Determination of trace elements in plant materials by slurry sampling graphite furnace AAS — some analytical problems

SummaryThe analytical conditions of cadmium, lead, nickel and cobalt determination in plant material by slurry sampling graphite furnace atomic absorption spectrometry (GFAAS) are presented. The results of stability tests for slurries prepared in different ways are also shown. The ratio of the amount of analyte found in the liquid phase to the total amount of analyte in the slurries is investigated. The determination results are calculated from aqueous standard calibration graphs (cobalt and nickel) or by the standard addition method (cadmium and lead). Statistical evaluation of the results from the certified materials indicate that the slurry method is both accurate and comparable in precision to the conventional wet-ashing procedure.

Study of matrix influence on supercritical fluid extraction of polar mercury species from solid samples

Methods for enhancing the extraction efficiency of mercury ion (Hg2+) and methylmercury (CH3Hg+) from various solid matrices using a home-made supercritical fluid extraction system combined on-line with atomic absorption spectrometric detection were investigated. The extraction of both spiked Hg2+ and CH3Hg+ from various simplified matrices, such as filter-paper, silica gel, aluminium oxide, starch, and cellulose, was achieved with the use of pure and methanol-modified supercritical fluid (CO2). For Hg2+, the effects of different kinds of derivatization and chelating reagents on the extraction efficiency were explored. It was demonstrated that both sodium tetraphenylborate and acetylacetone could be used as derivatization and chelating reagents with high efficiency of extraction from filter-paper using pure supercritical CO2. The effects of material (soil) particle size and a variety of organic substances such as humic acid, ethylenediaminetetraacetic acid and ammonium pyrrolidinedithiocarbamate on the extraction of Hg2+ or CH3Hg+ were also assessed. Some attempts were also made to evaluate the extraction behavior of spiked CH3Hg+ and Hg2+ in a natural soil sample. According to the effects of extraction pressure and time, the variation of the extraction efficiency of the mercury species of interest was found to be strongly dependent on their adsorption behavior on the sample matrix and the applied extraction parameters. Additionally, it was found that the extraction efficiency of CH3Hg+ could not be improved by using methanol-modified supercritical CO2. However, the extraction efficiency of Hg2+ from soil was significantly elevated from approximately 45 to 80%, if a suitable amount of methanol was used as a modifier.

Selective precipitation separation and inductively coupled plasma mass spectrometric determination of trace metal impurities in high purity silver.

A simple and rapid method for the determination of some trace element impurities in high purity silver, combining the isolation of analytes from the silver matrix with selective precipitation followed by ICP-MS determination was developed. On the basis of an extreme difference in the solubilities of the chlorides of silver and the other accompanying trace elements, silver can be separated completely through the addition of hydrochloric acid. The sample of silver was at first dissolved in 7 M nitric acid followed by addition of hydrochloric acid to remove the silver matrix by formation of a silver chloride precipitate, while leaving the trace element impurities in the solution, which was subsequently analysed by ICP-MS. Eleven elements (Al, Au, Cd, Co, Cu, Fe, Mg, Mn, Ni, Pb and Sn) were determined with good accuracy and precision. The limits of detection (based on the 3 sigma criterion) of these elements were 10(-1)-10(-3) ng g-1. The proposed method was successfully applied to the determination of metal impurities in high-purity silver samples (EM9465 and EM 9343) and validated by the analysis of NIST SRM 8171 (Fine Silver FS 14).

Determination of mercury in fluorescent lamp cullet by atomic absorption spectrometry

Two methods for the determination of mercury in fluorescent lamp cullet samples were developed. Cold vapour atomic absorption spectrometry (AAS) was applied to samples that were digested to dissolve the attached, mercury-containing phosphor. In the other method, solid phosphor material stripped from the glass cullet was used in a solid sampling technique employing electrothermal AAS with a specially designed ring chamber graphite tube. The results for the determination of mercury by the two methods were comparable. The relative standard deviations were 3.2–3.5% for the cold vapour AAS technique and 8.5–9.9% for direct solid sampling AAS at mercury levels of about 1.5 and 2.5 µg g–1, respectively. The proposed digestion procedure and mercury determination methods (especially the solid sampling AAS method) can be successfully applied to the rapid monitoring of the mercury level in fluorescent lamp cullet and facilitate its further use as recycled glass.

Investigation of activator (Mn, Sb) speciation in phosphors for fluorescent lamps

Abstract The speciation of antimony and manganese (activators for fluorescent lamp phosphors) in samples of commercial calcium halophosphate phosphors for fluorescent lamps was investigated. The total antimony content was determined by flame atomic absorption spectrometry (FAAS), and the antimony(III) content by controlled-current coulometric titration. A method for examination of manganese speciation was proposed. Manganese forms were investigated by the partial dissolution technique using various agents and by FAAS analysis. The proposed methods can successfully be applied for control of phosphor properties and manufacturing processes.