Analytical Sciences

Determination of Cobalt in Animal Feces by Tungsten Coil Atomic Absorption Spectrophotometry

Gisele S. LOPES*, Ana Rita A. NOGUEIRA** * , Pedro V. OLIVEIRA* and Joaquim A. NOBREGA*

*Departamento de Quimica, Universidade Federal de Sao Carlos, P. O. Box 676, 13560-970 Sao Carlos/SP, Brazil
**Centro de Pesquisa de Pecuaria do Sudeste, Empresa Brasileira de Pesquisa Agropecuaria, P. O. Box 339, 13560-970 Sao Carlos/SP, Brazil

An alternative analytical procedure for cobalt determination by tungsten coil electrothermal atomic absorption spec trophotometry (TCAAS) was developed to determine the liquid ruminal passage rate (turnover) of Co-EDTA in sheep feces. A matrix-matching procedure and a selective extraction of Co in 1.0 mol l^-1 HCl were evaluated in order to correct and minimize the interference effects caused by sample matrices. As application, six sheep received at the same time one dose of the marker (Co-EDTA); thier fecal samples were collected in intervals of 6 h during 90 h. The Co amounts determined in the dry sheep feces by TCAAS were compared with those obtained by a flow injection catalytic spectrophotometric method. The characteristic mass and the detection limit, both based on peak height absorbance, were 23.1 and 19.1 pg, respectively, for 10 ml of sample volume in the samples of sheep feces. The rsd was 0.5% for 10 consecutive injections of 20.0 mg Co l^-1. The accuracy was assessed by employing the paired t-test at 95% confidence level; there was no significant difference for Co content determined by TCAAS and by flow injection spectrophotometry. (Keywords: Tungsten coil atomizer, electrothermal atomic absorption spectrophotometry, cobalt, animal feces, animal nutrition)

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