Zeeman Effect Electrothermal Atomic Absorption Research Articles

Selenium measurement in human plasma with Zeeman effect electrothermal atomic absorption spectrometry: sample stability and calibration method

The dual aim of the present study is the investigation of the stability of plasma samples for selenium determination with time and temperature and the assessment of the calibration method. A comparative study is performed, using two calibration methods: standard addition to each sample and matrix matched curve. Our findings show that, in general, significant differences in the selenium content are observed when comparing the results obtained with these two calibration methods. Plasma samples stored at −20 °C are stable relative to the selenium content for a period of at least one year.

Comparison of ultrasound-assisted extraction, microwave-assisted acid leaching and reflux for the determination of arsenic, cadmium and copper in contaminated soil samples by electrothermal atomic absorption spectrometry

Extraction methods for the determination of arsenic, cadmium, and copper in contaminated soil samples by Zeeman effect electrothermal atomic absorption spectrometry have been compared. The determination of cadmium and copper in ultrasound-assisted aqua regia extracts of contaminated soil SRMs by ETAAS, using a mixture of NH4H2PO4 and Mg(NO3)2, for cadmium, and a mixture of Pd and Mg(NO3)2, for copper, as a matrix modifier, was carried out with high accuracy and precision (RSD < 5.1%). The analysis of SRM 2711 failed to obtain the certified concentrations of Cd and Cu by microwave and reflux methods, respectively. The determination of arsenic was performed successfully in low chloride concentrations by using a solution of 0.2% m/v NaNO3 as a matrix modifier. With chloride concentrations higher than 0.07 M the integrated absorbance signals of arsenic decreased significantly and the repeatability observed was as low as 15% for three replicate measurements. The chloride interferences on the determination of cadmium and copper were also tested with the addition of hydrochloric acid concentrations of up to 0.5 M without registering a significant decrease in the absorbance signals of the elements. The detection limits reached by the ultrasound-assisted extraction method were as low as 5, 0.04, and 0.26 mg kg−1 for arsenic, cadmium, and copper, respectively.

Sodium nitrate and tungsten as matrix modifiers for the determination of arsenic in shotgun pellets by electrothermal atomic absorption spectrometry

A method for the determination of arsenic in a complicated sample matrix by Zeeman effect electrothermal atomic absorption spectrometry using tungsten and sodium nitrate as matrix modifiers was developed. The determination of arsenic in SRM C2416 (Bullet Lead) and SRM 2710 (Montana Soil) by ETAAS using a mixture of palladium and magnesium nitrate as a matrix modifier failed to obtain the certified concentrations at the 95% level of confidence using the t-test. Both tungsten and sodium nitrate as matrix modifiers stabilized arsenic so that the certified concentrations of the SRMs were determined with high accuracy and precision (RSD < 4%). The high values of the regression correlation coefficients (r > 0.999), with low detection and quantification limits, were obtained in the calibration range 20–100 µg L−1. Sample matrix interferences can be eliminated by increasing the pyrolysis temperature to 1400 °C with tungsten and to 1500 °C with sodium nitrate matrix modification. The standard additions method was also carried out in the case of SRM C2416 in order to check the linear relationship between integrated absorbance and concentration for the calibration range used. The new method was utilized for the analysis of shotgun pellets.

Determination of tellurium in indium antimonide by slurry sampling electrothermal atomic absorption spectrometry

A method for the determination of tellurium dopant concentration in indium antimonide (InSb) by Zeeman effect electrothermal atomic absorption spectrometry using the slurry sampling technique was developed. The effects of chemical modifier type and mass on the absorbance-peak characteristics of tellurium in InSb slurried samples were studied. The atomization behavior of tellurium in InSb slurries could be greatly improved by the use of palladium nitrate as a chemical modifier. The detection limit of the optimized procedure was 0.4 µg g –1 . In the determination of tellurium at the concentration level of 16 µg g –1 , a relative standard deviation of 7% was obtained. Good agreement of the results obtained by the slurry sampling technique with those obtained by solution electrothermal atomic absorption spectrometry and inductively coupled plasma mass spectrometry was found.

Noise studies for detection limits for some electrothermal atomic absorption determinations and calculation of the optimal detection limit from one atomization

A simple statistical calculation, confirmed experimentally, shows that in Zeeman-effect electrothermal atomic absorption spectrometry the value of the integrated absorbance [graphic omitted] measured during a time t in the absence of neutral atoms can be broken down into two terms according to [graphic omitted] In this relationship mi is a constant, different for each atomization indicated by the index i, and x is a random value whose standard deviation can be calculated from the standard deviation and the number of measurements of the instantaneous absorbance. The calculation of mi allows one to decrease the error due to the integration of the blank signal and, therefore, to decrease the detection limit. If a non-negligible variation of the mi value is induced in the atomization step, calculation of mi after this step is more advisable. For the tested apparatus, the proposed post-atomization correction improves the accuracy of measurements and reduces the instrumental detection limit (IUPAC). An improvement by a factor of 5 is obtained, for example, for the detection limit of aluminium with an integration time of 3 s. Moreover, it has been shown for manganese and aluminium that the value of the detection limit obtained after correction is very similar to that calculated from a single atomization using the following equation resulting from statistical approximations: [graphic omitted] where s is the standard deviation of the instantaneous blank absorbances, Ts the sampling rate, tint the integration time, m the mass of metal injected and QA the corresponding measured integrated absorbance. The use of this equation, which is based on the measurement of the real experimental noise from one atomization, can offer an important saving of time.

Detection limits in Zeeman-effect electrothermal atomic absorption spectrometry

A theoretical and experimental study was made of the effect of photometric measurement error on the detection limits in Zeeman-effect electrothermal atomic absorption spectrometry. The results were used to develop a simple method for calculating the detection limits using four experimentally determined parameters, namely the baseline offset compensation time, the integration time, the light flux ‘energy’ and the background absorbance. A comparison was made of the calculated and measured detection limits for a number of elements in pure water solutions, and also in NaCl, blood and sea-water matrices. The calculated detection limits were found to be in agreement with the experimental data for all the elements studied. The performance of the method was demonstrated by optimizing the conditions for the determination of cadmium in blood.

Determination of impurities in germanium tetrachloride, germanium dioxide and high-purity germanium by Zeeman-effect electrothermal atomic absorption spectrometry

A procedure is reported for the determination of intermediate and final products obtained during the multi-stage process of germanium purification. Zeeman-effect electrothermal atomic absorption spectrometry was used and the optimum operating conditions were found to be the same for germanium tetrachloride, germanium dioxide and elemental germanium. The matrix was easily removed by evaporation, e.g., as germanium chloride, without loss of most of the impurities. Results are presented for 18 elements commonly present at trace levels. The detection limits are as low as 1 × 1014–1 × 1016 atoms cm–3.

Comparison of chemical modifiers for simultaneous determination of different selenium compounds in serum and urine by Zeeman-effect electrothermal atomic absorption spectrometry

The thermal stability of selenite, selenate, selenomethionine and trimethylselenonium was studied using different chemical modifiers in various amounts. The normally recommended amounts of nickel nitrate, magnesium nitrate, copper nitrate, copper nitrate mixed with magnesium nitrate, palladium nitrate and palladium nitrate in combination with magnesium nitrate were investigated. None of the studied modifiers stabilized the four species to the same extent. In aqueous solutions, addition of 2.7 µg of Pd or 7.5 µg of Pd + 5 µg of Mg(NO3)2 stabilized selenite, selenate and selenomethionine equally, while the sensitivity of trimethylselenonium was only 55% using palladium and 85% using palladium and magnesium nitrate. These chemical modifiers were used for the determination of selenium in serum. In aqueous solution, addition of 11 µg of Pd + 1128 µg of Mg(NO3)2 resulted in an equal stabilization of selenite, selenate and trimethylselenonium, while the sensitivity of selenomethionine was 15% higher. This chemical modifier was not applicable to serum and urine, as a white layer accumulated in the graphite tube during the experiments. Using the modifier containing 7.5 µg of Pd + 5 µg of Mg(NO3)2 for analysis of National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) Freeze-dried Urine the selenium concentration was 27.2 ± 1.3 µg l–1(certified value, 30 ± 8 µg l–1). The result of the analysis of the serum reference material. Seronorm, was 96.6 ± 1.8 µg l–1 of Se (recommended value 96 µg l–1). This chemical modifier is proposed as the best choice among the examined modifiers for determination of selenium in serum and urine.

Determination of urinary arsenic by electrothermal atomic absorption spectrometry with the l'vov platform and matrix modification

Total arsenic can be determined rapidly and simply in urine by dilution with a matrix modifier containing nickel and magnesium nitrate in nitric acid. The background correction capability of Zeeman-effect electrothermal atomic absorption spectrometry effectively nullifies nonatomic absorption by urine concomitants. Accuracy and precision of the method were evaluated by the determination of total arsenic in the National Bureau of Standards' SRM 2670, Toxic Elements in Freeze-Dried Urine, and commercially available lyophilized urine material. Deviations of determined concentrations from expected values ranged from about 4 to 18 ng ml −1 with standard deviations ranging from about 5 to 31 ng ml −1.

Semi-automated determination of chromium in whole blood and serum by Zeeman electrothermal atomic absorption spectrophotometry

Direct determination of normal and elevated levels of chromium in whole blood and serum can be achieved using Zeeman effect electrothermal atomic absorption spectrophotometry. Whole blood and serum levels of chromium were determined for an apparently healthy population and whole blood chromium levels for renal dialysis patients. Blood and serum specimens were diluted with distilled deionized water and Triton X-100. The analyses were performed utilizing air as the alternate gas to facilitate ashing in one of the char steps. Within-run precision studies for whole blood chromium determinations gave relative sd values of 4.75 and 4.65% for 0.358 and 0.172 μg/l, respectively. Within-run precision studies for the serum chromium analysis yield relative sd values of 5.26 and 2.67% for 0.156 and 0.300 μg/l, respectively. Detection limits were 0.025 and 0.018 μg/l for whole blood and serum, respectively. The mean chromium level found in whole blood and serum specimens from apparently normal individuals were 0.371 μg/l ( n = 37) and 0.130 μg/l ( n = 19), with ranges of 0.120–0.673 and 0.058–0.388 μg/l, respectively.

Zeeman Effect Electrothermal Atomic Absorption of Arsenic with Platinum as a Matrix Modifier

Since the charring temperature of As in environmental samples can be raised to 1320/sup 0/C with Pt, the sensitivity of determining As by ET-AAS is increased about 50% using Ni salt as a matrix modifier. The interference of most foreign ions is avoided, but PO/sub 4//sup =/ and SO/sub 4//sup =/ cause a depression and F/sup -/ and SiO/sup 3//sup =/ produce an enhancement of the As absorption. The method has been applied to pollution control and river sediment samples with satisfactory results. 16 references, 2 figures, 2 tables.

Zeeman effect electrothermal atomic absorption spectrophotometry with matrix modification for the determination of arsenic in urine.

Arsenic was determined in urine by electrothermal atomic absorption spectrophotometry using Zeeman Effect background correction and after matrix modification with 5% nickel nitrate. Mean recovery of urine samples spiked with 100 micrograms . L-1 dimethylarsinic acid was 97.9 micrograms . L-1. Within-run CV was 2.4%, between-run CV was 7.3% and the detection limit was determined to be 10.0 micrograms . L-1. The method can be used for the rapid screening of urine samples for elevated arsenic levels.