Study of parameters associated to solid sampling electrothermal atomic absorption spectrometry

Author(s)

Cassiana Seimi Nomura

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2006-03-03

Examining board members

Pedro Vitoriano de Oliveira; Érico Marlon de Moraes Flores; Claudimir Lucio do Lago; Ana Rita de Araújo Nogueira; Fábio Rodrigo Piovezani Rocha

• Advisor: Pedro Vitoriano de Oliveira

Abstract

In this work, a systematic study to evaluate the influence of the main parameters associated to solid sampling electrothermal atomic absorption spectrometry was done. The parameters evaluated were the sample drying and grinding, the particle size, the sample size and the homogeneity and their influence on Al, As, Cd, Cr, Cu, Pb, Ni and Zn determinations in bovine liver and muscle. Beyond these studies, methods for As, Cd, Cr and Pb determinations in hair and As, Cd, Cu, Cr, Ni, Pb and Zn determinations in urban particle matter were developed. The heating program optimization and the adoption of some strategies such as the use of chemical modifier allowed, in the most of cases, analyzing solid samples against aqueous calibration. Bovine liver and muscle were prepared following different drying procedures: (1) freeze-drying process and (2) drying in a domestic microwave oven followed by drying in a stove at 60oC until constant mass. Ball and cryogenic mills were used to grind the samples. All prepared materials presented good homogeneity to be applied in analysis of sample mass size lower than 100 µg, except to Pb. In this case, the minimal sample mass size was 600 µg. Bovine liver dried in a microwave oven followed by drying in a stove and ground in a cryogenic mill presented the best homogeneity. For Cu determination, 30 µg of this material could be used. Due to the capacity of SS-ETAAS in analyzing very low sample mass size, it was possible to evaluate the Cd and Pb distribution through the extent of the hair. This study showed that it is possible to retrieve information about past health issues, even if its cause has ceased. In this way, it can be applied in a forensic science. The urban particle matter analysis is related to certification process of the new certified reference material for microanalysis (SRM 1648a) in production process at National Institute of Standard and Technology (NIST). Results of homogeneity evaluation showed sample mass size lower than 50 µg can be used without affecting the precision and accuracy of the results. (AU)