DEVELOPMENT OF AN ELECTROTHERMAL METHOD F OR RAPID-DETERMINATION OF TRACE-METALS IN BUTTER BY ATOMIC-ABSORPTION SPECTROSCOPY - APPLICATION OF THE EXPERIMENTAL-DESIGN THEORY TO THE DETERMINATION OF COPPER

A rapid method of determination of metal traces in butter has been dev eloped by atomic absorption spectrometry with electrothermic atomisati on. Complete solubility at room temperature has been obtained with dis solving agent composed by butylamin/water/tetrahydrofuran (48/12/40). The solubility of butter in this solvent avoids the step of mineraliza tion, therefore a rapid assay could be performed by direct injection o f sample in the furnace. The selection of the significant factors is a llowed by application of experimental design. Factors for copper deter mination were optimized by means of a central composite plane in order to determine the response area. Optimization of thermic programmation lend to the optimal conditions: time of mineralization ramp temperatu re, 40 s; atomization temperature, 2450 degrees C. The detection limit is about 5 ppb and the lineary response is obtained to 200 ppb with a proportion of 15% butter in solvent (w/v).