A simple procedure for hydrodynamic injection in flow injection analysis applied to the atomic absorption spectrometry of chromium in steels

The proposed technique for hydrodynamic injection is based on commutation in a simple flow-injection system with only one peristaltic pump. Precise results (usually r.s.d. < 1%) are attained even when injected volumes are small (1–10 μl). Dead-volume effects are associated with the mechanical flexibility of the system and with diffusion; differences between effective sample size and the dimensions of the injection duct are emphasized, particularly for small volumes. The proposed technique is checked for a spectrophotometric model system and confirmed by the atomic absorption spectrometry of chromium in steels. With a sampling rate of 120 h^?1, the precision is better than 99% for chromium contents in the 0.0–30.0% (w/w) range. The results agree well with those obtained by i.c.p./a/e/s. and conventional a.a.s.