A Flow System for Spectrophotometric Multidetermination in Water Exploiting Reagent Injection

Abstract

A flow system for spectrophotometric multidetermination in waters is proposed. Reagent aliquots (25-75 muL) 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 fraction three-quarters 5.0 mg L-1), phenols (0.10 fraction three-quarters 1.0 mg L-1), nitrite (0.050 fraction three-quarters 0.50 mg L-1), sulphide (0.10 fraction three-quarters 1.0 mg L-1) and total iron (1.0 fraction three-quarters 5.0 mg L-1) without changing the flow manifold. Detection limits of 150 mug L-1 PO4(3-), 10 mug L-1 phenol, 2 mug L-1 NO2-, 20 mug L-1 sulphide and 15 mug 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.

Keywords

• water analysis
• flow analysis
• reagent injection
• multidetermination
• multi-element analysis
• cleaner analytical method