A flow system for spectrophotometric multidetermination in waters is proposed. Reagent aliquots (25-75 μL) were inserted into the sample stream, allowing up to 4.5-fold increase in sensitivity and an average 12-fold reduction in reagent consumption. The system allows the determination of phosphate (0.25 – 5.0 mg L-1), phenols (0.10 – 1.0 mg L-1), nitrite (0.050 – 0.50 mg L-1), sulphide (0.10 – 1.0 mg L-1) and total iron (1.0 – 5.0 mg L-1) without changing the flow manifold. Detection limits of 150 μg L-1 PO4(3-), 10 μg L-1 phenol, 2 μg L-1 NO2-, 20 μg L-1 sulphide and 15 μg L-1 Fe3+ were estimated at the 99.7 % confidence level. Coefficients of variation were lower than 4 % (n = 20). Results for river and lake water samples were in agreement with the obtained with flow systems with continuous reagent addition at the 95 % confidence level.
water analysis; flow analysis; reagent injection; multidetermination; multi-element analysis; cleaner analytical method
