Losses of Explosives Residues on Disposable Membrane Filters

摘要

Filtration of aqueous samples prior to analysis is a required part of many analytical protocols. In general, when a distinction is to be made between components in true solution (dissolved) versus total analyte content (dissolved plus suspended), filtration through a 0.45-micron filter is specified. A number of 0.45-micron disposable filters were tested for sorption of HMX, RDX, TNB, DNB, tetryl, TNT and 2,4-DNT. Both aqueous and mixed aqueous-organic solvent matrices were tested. For aqueous matrices, the Nalgene (green) cellulose acetate filter sorbed significant amounts of HMX, RDX, TNT and 2,4-DNT. The Gelman Acro LC25 filter, described as a naturally hydrophilic fluoropolymer, also sorbed significant levels of HMX, TNT and tetryl. Where sorption was found, losses were greatest for the first portion of filtrate passed through the filter and for filtration conducted slowly. Addition of 50% organic solvent prior to filtration eliminated sorption problems for all filters tested. When aqueous matrices are filtered, the recommended procedure is to discard the first 10-mL portion of filtrate and retain the second 10-mL portion for analysis. Keywords: TNB(1,3,5,-trinitobenzene); DNB(1,3-dinitrobenzene); Explosives; Organic compounds; Water pollution; Laboratory analyses.