Abstract
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.
Highlights
Nowadays, the consciousness regarding the use of water has increased due to the limited amounts of unpolluted freshwater sources and the high costs to produce potable water from seawater
The extension of the sample dispersion can be described by the dispersion coefficient (D), defined as the ratio of the sample concentration before (C0) and after dispersion (C): D = C0 / C
A simple and robust flow system was proposed for multiparametric spectrophotometric water analysis, exploiting reagent injection
Summary
The consciousness regarding the use of water has increased due to the limited amounts of unpolluted freshwater sources and the high costs to produce potable water from seawater. Most of the consumed water has been previously used.[1] The Brazilian legislation has established a set of criteria concerning the use of water, including the maximum allowed amounts of toxic species in natural and wastewaters.[2] A recent discussion has been focused on the establishment of taxes on the use of natural resources and disposal of wastewaters. Several analytical methods are available for environmental monitoring. In some circumstances, the chemicals employed are even more toxic than the species being monitored, resulting in some environmental impact.[3] a current trend is the development of methodologies less harmful to humans and to the environment (green analytical chemistry). As the substitution of all toxic reagents employed in chemical analysis is not an easy task, the reduction of the employed amounts should be the initial goal.[4]
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