Continuous sorbent preconcentration for the electrothermal atomic absorption spectrometric determination of ultratrace amounts of cobalt in milled wheat fractions

A method for the rapid determination of cobalt at ultratrace levels was applied in flour and flour byproducts (shorts and bran) obtained from various types of wheat that includes on-line preconcentration and electrothermal atomic absorption spectrometry is proposed. Solutions in 0.1 mol/L HNO(3) of milled wheat fractions subjected to wet ashing are preconcentrated in a straightforward flow-injection system by sorption on a RP-C(18) column following chelation. The eluent, ethanol, is carried by an air stream, and the chelate is eluted and collected in a 500 microL PTFE autosampler cup. The determination of cobalt features a precision (RSD) of 6% for a concentration of 0.2 ng/mL and a sensitivity (slope of the calibration graph) of 0.38 +/- 0.03 A s x ng/mL. The cobalt content in each type of wheat was found to be influenced by its geographical origin and texture. Also, it was found to depend on the amount of bran present in the milled wheat fraction. On the other hand, it is not significantly affected by the technological processes involved in wheat milling at a flour-producing factory.