Spectrex Corporation

Utility of the laser particle counter for determination of drinking-water toxicity

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Particle toxicity in various water samples depends on the mixture of toxicants in each sample. Toxicity values for different samples can be expressed using the new metric: Particle Toxicity.

Use of the Spectrex PC-2000 was the instrument of choice in enumerating the particle concentrations for the calculation of the particle toxicity of drinking-water and reference toxicant suspensions. Generation of Particle Size Distribution Graphics with the PC-2000 also provided information which characterized the particle concentration, surface area %, and volume % for specified particle-size subpopulations (1-2 m, 2-4 m, 4-8 m, 8-16 m, etc.). The parsing of surface area % into specific particle-size subpopulations is especially useful because the surface area of the particles is the parameter which determines the efficiency of toxicant adsorption for a given particle-size subpopulation. Further identification of the specific toxic agents observed in particles from each sample can be determined using EPA TIE Analyses2; the fractionation of toxicities into different chemical classes can be monitored using the Tetramitus Assay. Thus, the PC-2000 is an invaluable tool for whole particle toxicity studies of drinking-water and the identification of contaminants of concern.

Current regulations for water quality assessment express maximal allowable levels of single contaminants as a weight per unit volume metric; i.e., mg/liter. There is no provision for addressing the issue of toxicity of mixtures. Furthermore, there are no regulations which deal with particle toxicity. White, et.al,3 have demonstrated that for 50 industrial effluents, the particle toxicity, as measured by the E.coli SOS assay, is four orders of magnitude (10,000 X) greater than the soluble toxicity. Thus, the use of a particle toxicity metric offers a more relevant standard for the assessment of contaminants in drinking- and source-water.

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