Miniaturization of the Molybdenum Blue Method for the Spectrophotometric Determination of Phosphate in Water

Abstract

In aquatic environments, phosphorus is an essential nutrient, particularly in oligotrophic waters. This study evaluated the use of half the reagent concentration in the ascorbic acid method for determining phosphate in natural waters containing low levels of this analyte. In this work two procedures were tested on water samples and two analytical curves containing phosphate: the first using half the reagent concentrations of the ascorbic acid method (curve 1) and the second using the conventional reagent concentration (curve 2). Water samples were collected from various locations, including a lake, artesian wells, and drinking fountains, as well as from three different mineral water brands. Both calibration curves for phosphate demonstrated good linearity and sensitivity. Curve 1 showed higher sensitivity than curve 2. The detection limit was 0.026 mg L^-1 for curve 1 and 0.028 mg L^-1 for curve 2. The results indicated that using half the concentration of the reagents is sufficient for the determination of phosphate in waters with low concentrations (< 0.1 mg L^-1). Although the volume of waste produced is the same, the reduction in the amount of chemical reagents represents a decrease in the costs of the procedure.