Die vloei-inspuitanalise van sekere determinante in oppervlak- en grondwater

Abstract

Flow injection analysis (FIA) is a continuous flow technique, similar to segmented flow analysis (SFA). FIA is based on reproducible sample injection, accurate timing and controlled dispersion. This technique is very versatile due to the control of the variables on the dispersion of the flow system and can be applied to a number of applications. It is especially suitable for pharmaceutical and water samples. A comparative study has shown that the sample frequency of FIA methods significantly higher than that of the correspond i ng SFA methods. SFA, however, is an established method that has been successfully used in routine water laboratories for the past three decades. FIA methods were developed for the determination of phosphate, silica, nitrate, nitrite and ammonium in surface and ground waters. Standard Auto Analyzer modules were used for the colorimetric determination of the above-mentioned constituents. The colorimeter was equipped with a double type flow cell. The advantage of this type of flow cell is the elimination of any air bubbles that may occur in the flow system. The double section, however, causes an increase in the carry over and therefore lowers the sample frequency. A liquid chromatography valve was used for the sample injection. The valve was controlled by a locally constructed timing device. The phosphate and silica determinations were based on the molybdenum blue method using respectively tin(II) chloride and ascorbic acid as reducing agents. A sample frequency of 90 samples/h was maintained for both methods.