Nickel as a chemical modifier for sensitivity enhancement and fast atomization processes in electrothermal atomic absorption spectrometric determination of cadmium in biological and environmental samples.

A systematic study of the efficiency of protons, Ni, Pd and Th as chemical modifiers for the determination of cadmium by electrothermal atomic absorption spectrometry (ETAAS) using fast temperature programs was made for platform atomization. A comparison was made in terms of the salt type, absorbance-time profiles and elimination of the sodium chloride interference. The results were adapted to develop a method for the ETAAS determination of cadmium in biological and environmental samples. The highest sensitivity to determine cadmium in biological and environmental samples was obtained using nickel (together with protons) as a chemical modifier. The accuracy of the method was tested by the determination of cadmium in different certified reference materials. The best detection limit and the characteristic mass of Cd were found to be 0.03 ng mL(-1) and 0.35 pg, respectively.     

Determination of cadmium in biological and environmental samples by slurry electrothermal atomic absorption spectrometry

The retention of cadmium by the bacteria Escherichia coli and Pseudomonas putida was optimized in order to develop a rapid and selective preconcentration method for cadmium from biological and environmental samples prior to determination by electrothermal atomic absorption spectrometry. Living and lyophilized cells for both bacteria were used, but the method using dead cells shows better analytical capabilities. Cadmium from aqueous solutions is easily retained on the outer membrane of both bacteria in the pH range 4-10, although the selected working pHs for E. coli and P. putida were 5 and 9, respectively. Cadmium retained by the bacteria was dispersed in 3.5 M nitric acid and the slurry was introduced directly into the graphite tube. The best sensitivity and detection limit were obtained for E. coli (0.03 ng ml(-1) and 0.04 ng ml(-1) respectively, in the absence of any chemical modifier). A strong spectral interference from nickel chloride was found and methods to overcome it were developed. The proposed extraction procedure was tested by the determination of cadmium in different standard biological and environmental samples.     

The226Ra/Ba-ratio as indicator for phosphogypsum contributions to226Ra levels in sediments

Phosphogypsum discharges by phosphate-ore processing industries pollute sediments of the Rotterdam harbour area with²²⁶Ra. Direct measurement of this radionuclide in sediments does not provide a reliable indication of the elevation of the levels, since²²⁶Ra levels in sediments depend on the particle size. To eliminate the size effect, the²²⁶Ra/Ba ratio in sediments was tested as a possible indicator for the²²⁶Ra in the discharges. The results indicate almost a doubling of the²²⁶Ra levels in sediment samples due to phosphogypsum discharges. The contribution of phosphogypsum to the sediment mass was calculated in the order of a few percent equivalent.     

Copper and iron interactions with angiotensin-converting enzyme inhibitors. A study by fast-atom bombardment tandem mass spectrometry

Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd.     

Determination of beryllium by electrothermal atomic absorption spectrometry using tungsten surfaces and zirconium modifier

Electrothermal atomization of beryllium from graphite and tungsten surfaces was compared with and without the use of various chemical modifiers. Tungsten proved to be the best substrate, giving the more sensitive integrated atomic absorption signals of beryllium. Tungsten platform atomization with zirconium as a chemical modifier was used for the determination of beryllium in several NIST SRM certified reference samples, with good agreement obtained between the results found and the certified values. The precision of the measurements (at 10 μg L⁻¹), the limit of detection (3σ), and the characteristic mass of beryllium were 2.50%, 0.009 μg L⁻¹ and 0.42 pg, respectively.     

Performance-improvement in57Fe-DCEMS by an optimized scintillation counter

Applications of DCEMS or ICEMS for UHV studies of surfaces and interfaces are often severely limited by long recording times. To clarify the practical means to shorten this time, we introduce the “statistical utility rate” α characterizing the statistical quality of a given measurement. By improving detection efficiency and reducing background contribution simultaneously, we have developed an extremely low-noise scintillation detector (Hamamatsu R1635-02 or R2557 photomultiplier with P-47 thin-layer phosphor). Performance comparison with a channeltron by⁵⁷Fe-DCEMS measurements on an 90% enriched⁵⁷Fe foil with 7.2 keV electrons reveals a measuring time gain over an order of magnitude in favour of the scintillation e-detector. Improvements achievable for samples with normal isotope abundance are higher than for enriched ones.