Ernst Lücker

Analytical quality control by solid sampling graphite furnace atomic absorption spectrometry in the production of animal tissue reference materials : bovine liver, teeth, bone, muscle, blood and equine renal cortex

SummaryThe function of solid sampling graphite furnace atomic absorption spectrometry (SS-GFAAS) in the laboratory-internal preparation, production and standardization of several animal tissue reference materials is described. SS-GFAAS is successfully applied in the production of a bovine liver reference material with a low content of Pb and Cd. The lab-internal production of 5 bovine teeth and 2 bovine bone reference materials illustrates some of the basic problems entailed in the analysis of Pb in osseus matrices and in the production of the reference material itself. In the production of muscle tissue reference material focal or generalized calcification is a serious source of endogenous Pb contamination. This is shown, by way of example, in the calcification of the larval states of Taenia saginata (Cysticercus bovis) in the bovine muscle. Finally, as further examples of the application of SS-GFAAS, the lab-internal production of reference material from bovine blood and equine renal cortex is described.

Sources of error in direct solid sampling Zeeman atomic absorption spectrometry analyses of biological samples with high water content

Abstract Analytical errors were quantified in the direct analyses of trace elements in samples with high water content by means of solid sampling atomic absorption spectrometry with Zeeman effect background correction (direct SS-ZAAS). Time versus mass curves for HNO 3 (0.1 mol 1 −1 ), blood, kidney and liver at different temperatures (+20, +4, −20°C) and mass input (0.07 to 42 mg) were observed. Following a stabilization period, mass losses appeared to be nearly linear and independent of input mass. By means of a function using observed stabilization time and mass losses a 10% increase in analyte content was calculated as occurring at and below 0.06 mg. Experimentally, 10% increases were found to occur within a range 0–0.07 mg for weighed Cd solutions (0.1 and 0.2 ng mg −1 in 0.1 mol 1 −1 HNO 3 at 5°C). An automated solid sampling system consisting of microbalance, dispenser, transport system and electronics was integrated in the experiments. Manual working time and the necessity of operator presence were reduced by at least 80%. Performance and capacity compared well to the manual SS-ZAAS mode. Automated SS-ZAAS analysis in fresh animal tissues is proposed for use as a screening and reference method in official residue control.

Distribution of Pb and Cd in the liver of the mallard — direct determination by means of solid sampling ZAAS

SummaryThe distribution of Pb and Cd in livers of the mallard (Anas platyrhynchos) was analysed by means of solid sampling AAS with direct ZEEMAN effect background correction (SS-ZAAS). In the case of Pb the analyses of variance indicated a negligibly low influence of heterogeneity on the final result. In a range of 0.03–1.2 ng/mg fresh matter (sample sizes: 0.4–15.7 mg) the variance due to heterogeneity proved to be distinctly lower than the residual experimental error. The anatomical location of the sampling site remained without significant influence. In the case of Cd (0.09–2.4 ng/mg, sample sizes: 0.05–14.1 mg), however, an increased degree of heterogeneity was observed in 50% of the livers. Here, the influence of heterogeneity can be effectively reduced by means of an adequate sampling scheme, which was shown by a comparison of methods including SS-ZAAS and a sample decomposition method.

Feststoffanalytik mit Autoprobe-GFAAS

SummaryA new graphite system has been developed for GFAAS combining the ‘autoprobe technique’ and solid sampling analysis. Based on previous studies with D2-background corrected solid sampling GFAAS it has been demonstrated that the determination of Pb, Cd, Zn, Mn and Cu in various matrices of mainly biological origin is possible and practicable by means of solid sampling autoprobe GFAAS. Accuracy and precision are comparable to known solid sampling GFAAS systems.

Die Bestimmung von Schwermetallen in nativer Nierenmatrix mittels Feststoffanalytik und Atomabsorptionsspektrometrie

SummarySolid sample analysis by Zeeman AAS is a method which allows rapid determination of lead and cadmium in small amounts of fresh renal tissue without time consuming chemical digestion. The renal cortex is preferable to other tissues or the whole kidney to optimize standardization of sampling, homogeneity, element concentration and microsampling. The analytical quality is sufficient to detect limit concentrations of Pb and Cd in the kidney and ‘normal’ levels as well.

Sampling Strategy and Direct Solid Sampling Electrothermal Atomization Atomic Absorption Spectrometric Analysis of Trace Elements in Animal Tissue

The influence of analyte distribution on analytical results of direct solid sampling and electrothermal atomization atomic absorption spectrometry with direct Zeeman-effect background correction (SS-ZAAS) was studied with the use of nonhomogenized livers of mallards and fallow deer and hierarchic sampling schemes. Significant differences were observed by means of the analysis of variance in lead content of left and right lobes as well as of randomly distributed sampling sites of a deer liver. For the first time SS-ZAAS distribution analysis gave variances dominated by analyte distribution. The distribution analyses of mercury in livers of mallards gave significant effects of sampling sites in 6 out of 10 livers; however, in all cases variance as caused by analyte distribution was observed to be lower than residual variance. Allowing for heterogeneity, the minimal total variance is reached for a given number of replicates when each test sample is taken from a different site of the organ. Despite increased imprecision, the uncertainty of direct solid sampling is thus minimized effectively.

Distribution of Pb and Cd in equine liver : direct determination by means of solid sampling ZAAS

SummaryThe distribution of Pb and Cd in equine livers (n=7) was analyzed by means of solid sampling ZAAS. In all livers the analysis of variance indicated a negligibly low influence of heterogeneity on the final result. The results of solid sampling ZAAS determination of Cd and Pb in fresh non-homogenized livers (n=49) agreed with the results of a conventional sample decomposition method after homogenization of the respective sample material.

Solid sampling ZAAS determination of endogenous Pb contamination in muscle tissue caused by calcification

SummaryFocal endogenous Pb contamination in bovine muscle tissue can be caused by Cysticercus bovis (C. bovis), the larval stage of Taenia saginata. 79 samples of cysts and the respective muscle tissues were analyzed by means of solid sampling Zeeman atomic absorption spectrometry (SS-ZAAS). In calcified cysts of C. bovis, the Pb content was up to 1864 times higher than in the directly surrounding muscle tissue. The maximum Pb content of the cysts was 3.0 mg/kg, that of the muscle tissue 0.02 mg/kg. There is a significant positive correlation between the stage of calcification and the Pb content in the cysts (Spearman rank correlation: r=0.869, P≤0.01). Compared to the surrounding muscle tissue, even in non-calcified early stages of the cysticeri, there is a distinctly elevated Pb content. Non-focal endogenous Pb contamination in muscle tissue can be caused by calcification of the tissue itself or by calcification of its blood vessels. In the latter case the difference in the Pb content of muscle tissue (myocardium) and that of the regions which are prone to calcification (endocardium, endocardial platelets) proved to be highly significant with a ratio of up to <50.SS-ZAAS proved to be well suited for the determination of Pb in endogenously contaminated muscle tissue where sample decomposition methods may lead to incorrect results due to larger sample sizes and sample homogenization.

Solid sampling analysis by means of autoprobe-GFAAS

SummaryA recently developed solid sampling graphite system for automatic probe atomisation (SAP-GFAAS) was applied for the direct determination of Pb and Cd in untreated bovine liver matrix.The study was based on 30 livers with a low content of lead (0.045 to 0.27 μg Pb/g fresh matter) and of cadmium (0.031–0.24 μg Cd/g fresh matter). The basic comparative data for the evaluation of the SAP-GFAAS method were supplied by a standardized GFAAS method with preliminary sample homogenization and matrix decomposition. Additionally, data were obtained by two further solid sampling methods: a front entry graphite system with direct Zeeman effect background correction and a side entry graphite system with high-energy deuterium continuum background correction. The combination of the autoprobe technique and solid sampling was shown to provide analytical results — in terms of handling, accuracy and precision — comparable to those obtained by means of the ‘conventional’ solid sampling systems. Differences between the results of the sample decomposition method and the solid sampling methods, as well as between the three solid sampling methods must be regarded as being of no practical significance.