Abstract: A slotted stainless steel tube when used in air-acetylene flame increses the residence time of atoms in the light path of an atomic-absorption spectrometer, thus increasing the analytical sensitivity. With this technique copper and zinc were determined in serum diluted 1:20. Rapid accurate analyses can be achieved by using continuous aspiration. Use of aqueous standards resulted in recovery for copper and zinc of 92-110.9%. Coefficient of variation of 2.7% and 3.6% respectively.