Application of Green Chemistry: A Miniaturized Procedure for Analysis of Dissolved Phosphate

Abstract

The objective of this study was to determine if the volume of sample used for analysis of soluble reactive phosphate (SRP) could be reduced from 100 mL (as per a widely used standardized procedure) to 50 or 10 mL to reduce the amount of hazardous waste generated from routine analysis of SRP in water samples from rivers, streams, and ponds in an urbanized landscape, in accordance with the principles of “green chemistry” and the Pollution Prevention Act of 1990. The ascorbic acid-molybdate blue method of Murphy and Riley (1962) was used to determine the concentration of SRP in water samples collected from the East Branch of the DuPage River and from two ponds on the campus of Benedictine University. Mean concentration of SRP determined using a 10 mL sample volume of DuPage River water (x = 1,051 μg PO4-P/L) was significantly greater than the 100 and 50 mL sample volumes, which were not significantly different from each other (x = 1,002 μg PO4-P/L); however, the difference in SRP concentration between 10 mL and 100 and 50 mL sample volumes was only 5%. There was no significant effect of sample volume on SRP concentration for slough or storm water pond samples, but these two pond systems had a low SRP concentration (<3 μg PO4-P/L). The relationship between absorbance and SRP concentration in the ascorbic acid-molybdate blue method was examined between 0 and 2,000 μg PO4-P/L; absorbance was asymptotic between 500 and 2,000 μg PO4-P/L. The results of this study show that the sample volume for analysis of SRP in DuPage River water with the ascorbic acid-molybdate blue method can be reduced by 50% (i.e., reduced from 100 mL to 50 mL) without loss of accuracy, but that samples must be diluted to reduce the concentration of SRP to within the limits of the procedure. The reduction in sample volume represents a substantial reduction in the volume of hazardous waste that is generated, and the overall cost per sample, for routine analysis of SRP in the DuPage River.