Hydrodynamically limited precision of gradient techniques in flow injection analysis

Based on the law of error propagation, a general expression is derived to study theoretically the hydrodynamically limited precision associated with each single element of fluid in a concentration profile in flow injection analysis. Convolution of the injection and residence time distribution functions is used to obtain response functions for a homogeneously stirred mixing chamber and for a straight capillary tube. The effects of stochastic variations on overall precision by sample introduction, pumping and timing are elucidated and compared with experimental findings. Resulting practical implications for the use of these two dispersing elements are outlined.