Determination of cobalt in urine by FI-ICP-OES prior on-line preconcentration

FARIAS, GUSTAVO F.; WUILLOUD, RODOLFO G.; MOYANO, SUSANA; GÁSQUEZ, JOSÉ A.; OLSINA, ROBERTO A.; MARTINEZ, LUIS D.

Florianópolis

Simposio; SEVENTH RIO SYMPOSIUM ON ATOMIC SPECTROMETRY; 2002

Universidade Federal de Santa Catarina

Cobalt is considered an essential trace element that is required in the normal diet of man in the form of vitamin B12 (cyanocobalamin). For this reason cobalt has been used in the treatment of anemia. However, the use of cobalt supplementation has been associated with toxic side effects such as cardiomyphathy. As cobalt often occurs in waters and tissues in complicated matrices at extremely low levels, analyte preconcentration and/or matrix separation is required prior to most analytical techniques.Atomic absorption spectrometry with electrothermal atomization (ETAAS) has become the most appropriate technique for its determination. However, ETAAS often suffers from matrix interferences when it is applied to the analysis of biological materials. Besides this technique is very well suited to determine cobalt levels found in the urine of occupationally exposed persons, but for measuring normal urine levels preconcentration steps are required.Inductively coupled plasma optical emission spectrometry (ICP-OES) is widely recognized as a suitable technique for the determination of trace elements. On the other hand, if conventional ICP-OES is used, the low level of cobalt in urine is not compatible with the detection limit of this technique. In order to achieve accurate, reliable and sensitive results, preconcentration and separation are needed when the concentrations of analyte elements in the original material or the prepared solution are too low to be determined directly by ICP-OES. Preconcentration is an effective means for extending the detection limits of ICP-OES methods. However, when practiced manually in the batch mode, the operations are usually too tedious to be compatible with the ICP-OES measurements.In the present work, a method for preconcentation and determination of cobalt using a microcolumn filled with a macroporous resin Amberlite XAD-7 is proposed. Cobalt was retained under the form of Co-(5-Br-PADAP) complex. The determination was performed using ICP-OES associated with a FI methodology.The cobalt was preconcentrated as cobalt-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol [Co(II)-(5-Br-PADAP)] complex, at pH 9.5. The limit of detection (LOD) obtained under the optimal conditions was 50 ng/L. The method was successfully applied to the determination of cobalt in urine samples.