A method for air sample analysis of ethylene-thiourea (96457) (ETU), and tetramethyl-thiourea (2782914) (TMTU), was tested. ETU was collected on 37 millimeter (mm) polyvinyl-chloride membrane (5 microns pore size) and 37mm mixed cellulose esters membrane (0.8 micron pore size) filters. TMTU was sampled with standard size midget impingers containing 15 milliliters of distilled water. Pentacyanoaminoferrate reagent was added to the filter extracts and impinger contents. The complexed sample solutions were analyzed after 30 minutes with a spectrophotometer at 590 nanometers, using 5 centimeter quartz cells. Correlations with a calibration curve were linear for both compounds up to 150 micrograms per 16.5 milliliters. Color was stable up to 3 hours. Recovery of ETU was good on both filters, but TMTU could not be extracted with water or methanol. The detection limit was 0.75 micrograms per sample for ethylene- thiourea and 3 micrograms per sample for tetramethyl-thiourea. The author concludes that TMTU probably reacted with the filter and prevented extraction. This test method can be used for other thiourea based compounds.
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