It has been developed a fully mechanised procedure for the determination of selenium in waters employing a LED based spectrometer and solenoid multi-pumps as solution propelling devices. The proposed method is based on the reaction of selenium with potassium iodide in an acidic medium to liberate iodine, which oxidizes Variamine Blue to form a violet-colour species which absorb at 530 nm. The system was mechanised using the multicommutation process and a stopped flow strategy in the final step reaction. The analytical curve was linear between 0.010 and 0.500 mg L-1, with an equation ΔA = 0.501 (± 0.004) C and r = 0.999. The limit of detection (3σ/S) obtained for the proposed method was 0.004 mg L-1. The relative standard deviation for Se solutions of 0.050 and 0.200 mg L-1 (n = 4) were 1.6 and 1.8% respectively, the sampling throughput was 23 determinations per hour, and accuracy was 95% probability level.
selenium; water; multi-pumping; mechanised flow system; LED-photometry; multicommuted flow system
