Capillary diameter and rate of aspiration as factors affecting the accuracy of zinc analysis in serum by atomic absorption spectrophotometry

The importance of the internal diameter of the capillary tubing used for aspiration of samples into the atomizer-burner of an atomic absorption spectrophotometer has been demonstrated particularly for analysis of serum or plasma. The concentration of zinc in serum diluted 1 2 was significantly underestimated when aspirated through the commonly used capillary of 0.38 mm internal diameter. Substitution of a capillary having an internal diameter of 0.58 mm or increasing the dilution to 1 3 gave accurate measurements. Air and fuel flow settings affected the performance of the smaller capillary to a greater extent than the larger. Direct measurements of zinc in serum diluted 1 2 thus are feasible when made by aspiration through a capillary of 0.58 mm internal diameter with appropriate fuel and air flow setting.