Fundamental aspects of various noise sources in flameless atomic absorption have been considered and the measurement system appeared to be shot noise limited. The influence of time constants of the measurement system, modulation frequency of the primary source, and heating rate of the sample cell on both noise level and signal-to-noise ratio have been experimentally investigated. Furthermore, the effect of the bandwidth of the amplifier-recorder system on analytical parameters, such as detection limit, sensitivity, and linear working range of the calibration curves, has been studied. Detection limits for undistorted signals, optimum signal-to-noise ratio, and highly distorted signals are reported.
Direct determination of gold, cobalt, and lithium in blood plasma at the ppm level was performed by means of flameless atomic absorption using the carbon rod atomizer. The major causes of variability-vir. sample introduction and alteration of the properties of the graphite-have been experimentally investigated. A remarkable gain in precision has been obtained by means of instrumentally controlled sample introduction. Regression analysis has been applied to the calibration curves and confidence limits were calculated. Fluctuations of the absorbance signals proved to be affected not only by the reproducibility errors but also by procedural errors. A comparison of analytical results obtained with both the carbon rod atomizer and a gas stabilized dc arc is given for gold and cobalt analyses in blood plasma.
SUMMARY.Aluminium in human tissues has been determined by flameless atomic absorption spectroscopy (AAS). Tissues were dried at l lff'C and digested with concentrated nitric acid at SO°C overnight. After dilution with distilled water the samples were measured. The aluminium levels of the controls (healthy individuals who died as a result of an accident) appeared to be: grey matter 2·1 ± 1·0 (mean±SD), white matter 1·7±0·S, spinal cord 3·3±1·S, kidney 1·9±0·7, heart 2·1±1·1, vertebral cortex 1·9±1·8, and vertebral trabeculae 3·1±1·8 Ilg/g dry weight. For a patient with dialysis motor neuropathy significantly higher values were found. Comparison with values in the literature shows that our reference values are in agreement with published results obtained by flameless atomic absorption spectroscopy.
SUMMARY.Urinary cobalt was determined by flameless atomic absorption spectroscopy. Three methods were compared: (i) direct analysis with deuterium background correction after l l-fold dilution with distilled water (method D), (ii) analysis with deuterium background correction after extraction of cobalt from the urinary matrix in organic solution (method E), and (iii) direct analysis with Zeeman background correction (method Z). The detection limit of the direct analysis of urinary cobalt with deuterium background correction was 6 Ilg/L, this appeared to be insufficient for the determination of reference values and moderate enlarged cobalt values. Comparison of the extraction method and the Zeeman method revealed that these methods have similar reference values, detection limits, precision and recovery.Cobalt is an essential trace element that is required in the normal diet of man as a component of vitamin B12. In larger doses cobalt is toxic and is associated with a wide spectrum of clinical syndromes such as pneumoconiosis, allergy, cardiomyopathyI and, in animals, cancer. I It is therefore of interest to monitor this metal in the biological fluids of exposed workers. Cobalt is rapidly excreted and concentrations in urine and serum show a close correlation. 2
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