Changes in zinc and lead content of rat hippocampus and whole brain following intravital dithizone treatment as determined by flameless atomic absorption spectrophotometry.
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A microtechnique is described for determination of lead and cadmium in blood (0.1 ml) and in urine (0.2 ml) using extraction into methyl isobutyl-ketone after chelation by ammonium pyrrolidine dithiocarbamate. Mineralization, precipitation of proteins or addition of hemolysing reagents are not necessary. Blood is hemolysed by addition of deionised water. pH of urine is fixed by a pH 5 buffer. This microtechnique is simple, rapid, reproducible and suitable for routine analysis. In healthy subjects it gives values comparable to data of other workers: blood 158 microgram/l lead (s = 40, n = 18); 0.7 microgram/l cadmium (s = 0.3, n = 10); urine 16 microgram/l lead (s = 9.4, n = 10); 0.5 microgram/l cadmium (s = 0.3, n = 10).
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A micromethod is described for the analysis of zinc in plasma or serum by electrothermal atomisation and graphite furnace utilising less than 20 microliters sample volume. The sample matrix introduced an error when aqueous standards were used. Therefore standards were made up in serum which had been treated with Chelex 100 to remove as much zinc as possible. The residual zinc (less than 0.125 mg/l) was determined by flame analysis using the method of additions and each standard assigned a value equal to the sum of the residual zinc and the amount added. Furnace analyses using standards made up in Chelex-treated serum compared favourably with flame analyses over the whole range, and recovery experiments gave 98 +/- 2% of the expected value with 95 +/- 6% recovery of the added zinc. The within-batch coefficient of variation was 2.5%, day-to-day variation 5.6%. The mean concentration of zinc in paired samples of plasma and serum from 50 adults analysed by flame with viscosity-matched aqueous standards were: plasma (mean +/- SD) 0.821 +/- 0.085 mg/l; serum 0.821 +/- 0.07 mg/l. The same samples were analysed in the graphite furnace using serum standards, and the results were: plasma 0.812 +/- 0.082 mg/l; serum 0.815 +/- 0.08 mg/l. In contrast to earlier reports we were unable to demonstrate a significant difference between plasma and serum zinc concentration in the paired samples.
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A simple and rapid method, avoiding preliminary extraction, is described for the determination of Co in plant samples. The factors influencing the mineralization steps and the interference of major elements are investigated. The described method gives a recovery in the range 100-110%. Use of the standard addition method avoids interference from Ca and Fe. In the range 0.1-1 ppm (dry basis), Co can be determined with a precision of 5%. The detection limit of the method is 0.02 ppm of Co in forages.
Quality control materials and participation in proficiency testing programmes were used for assessing the long-term performance of our blood lead analysis. The accuracy and precision of the blood controls, Metals 1 and 2 from the Behring Institute, were evaluated over a 1-year period. The accuracy of the method was also monitored by the Centers for Disease Control (CDC) Blood Lead Proficiency Testing Programme over a 3-year period. Nearly 85% (28 out of 33 samples) of our results were within +/- 5% of the CDC reference values. There were excellent correlations between our results and the target values of several proficiency testing samples, with correlation coefficient values of 0.9959-0.9970. The method was used for the screening of blood lead in children in conjunction with microsampling techniques.
Three wet digestion procedures, namely, nitric acid/sulphuric acid, nitric acid/hydrogen peroxide and nitric acid/perchloric acid were compared for their relative efficiency in determining cadmium and lead in marine biological tissues. The nitric acid/perchloric acid procedure was the most efficient, whereas the nitric acid/hydrogen peroxide procedure was the least efficient. The nitric acid/sulphuric acid procedure was also found to be effective but there was a problem with the method as the presence of sulphuric acid in the matrix markedly suppressed the absorbance signals especially for lead analysis and thus reduced sensitivity. The addition of ascorbic acid as matrix modifier improved sensitivity. However, this analysis still required the standard addition method. No apparent interferences were encountered for cadmium analysis.
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