Sheila Alves

Determination of Cd and Pb in biological reference materials by electrothermal atomic absorption spectrometry: A comparison of three ultrasonic-based sample treatment procedures

Three different ultrasonic-based sample treatment approaches, the automated ultrasonic slurry sampling, the ultrasonic assisted acid solid-liquid extraction (ASLE) and the enzymatic probe sonication (EPS) were compared and discussed for the determination of Cd and Pb by ET-AAS in biological reference materials. The sample mass chosen to perform the analysis was 10mg and the liquid volume was 1ml of nitric acid 1M. The best results were obtained with the slurry procedure with which it was possible accurate and precise determination of the Cd and Pb content in four of the five reference materials studied. Optimum performance (total metal extraction) of ASLE assisted by ultrasound for Cd was only achieved in two of the four materials assessed whereas total Pb recovery was only possible in three of the five samples. Total extraction with the enzymatic probe sonication was only obtained for Cd in oyster tissue. Neither ASLE nor EPS were able to extract Cd or Pb from spruce needles. Pb concentration obtained after EPS was found to be highly dependent from sample centrifugation speed and time.

Determination of nickel, calcium and magnesium in xylem sap by flame atomic absorption spectrometry using a microsampling technique.

INTRODUCTION Knowledge of xylem sap chemical composition is important to the understanding of translocation, detoxification and tolerance mechanisms. However, the small amount of sample available often hampers its characterisation. Hence, low volume consumption techniques are needed for xylem sap analysis. OBJECTIVE To develop a microsampling technique for the determination of elements in xylem sap from different plants by flame atomic absorption spectrometry (FAAS). METHODOLOGY The microsampling device was optimised in terms of sample volume and integration time. The analytical characteristics of the microsampling technique (micro-FAAS) were established and compared with those of FAAS with traditional continuous nebulisation. The method was validated by means of an independent technique. RESULTS Ca, Mg and Ni were determined in a 50 microL aliquot of xylem sap solution/element that was introduced directly into the flame via the microsampling accessory. Good precision was obtained with relative standard deviations of 1.1, 0.6 and 2.3% for Ca, Mg and Ni, respectively. Matrix effects resulting from the physical characteristics of the samples and possible chemical interferences caused by phosphate and/or sulphate were ruled out. CONCLUSION A simple, rapid and reproducible microsampling technique coupled to FAAS was developed and successfully applied in the determination of Ca, Mg and Ni in xylem sap.