Linear working graphs in blood lead determinations with the Beckman flameless atomic absorption cuvet

Working graphs are generally nonlinear when the longitudinal flameless atomic absorption cuvet is used. Such nonlinear curves make it difficult to determine the amount of lead in blood by the method of additions, because of inaccuracies in extrapolating the graph to zero absorbance. This paper describes a method for obtaining linear graphs by making use of opacity (the reciprocal of transmittance, or antilog of the absorbance) instead of absorbance. Because no deuterium arc background corrector is available for the Beckman Model 444, background was correlated by reading the opacity at a nonabsorbing line, 287.3 nm, and subtracting the opacities. A separate reagent-blank correction for lead must also be made.