Automation of the standard additions method in flame atomic absorption spectrometry.

Two manifolds allowing the automation of the standard additions method in flame atomic absorption spectrometry by using two computer-controlled variable-speed peristaltic pumps operating in a programmed way are presented in this article. One of the pumps increases and the other decreases its turning speed linearly with time, so that the flow-rate supplied to the nebulizer is constant. In the first manifold, one pump moves the sample solution, while the other pump propels a standard solution, so that a continuously changing on-line mixture of both the solutions is obtained. In the second manifold, both pumps, one of which also pumps a standard solution, while the other pumps a diluent solution, propel the sample solution. This second manifold that exactly reproduces the standard additions method, is automatic and allows releaser solutions to be used. Both the procedures present the additional advantage over the conventional batch procedure of the very high number of data that can be acquired by the computer. The theoretical background of both manifolds is presented and their correct operation is experimentally verified.