pec

9 Potentially Explosive Chemicals Chemicals stored beyond the recommended shelf life may be used if testing shows peroxide concentrations less than 100 ppm. Testing results shall be recorded on the container. Test all peroxide formers prior to distillation, regardless of age. If peroxides are detected, at any concentration, the solvent shall be treated (see Appendix 3) prior to distilling. IMPORTANT! Never test containers of unknown age or origin. Undated bottles may contain concentrated peroxides, or peroxides may have crystallized in the cap threads, which may explode when opening the bottle. Call EH&S or ESH for managing undated containers. Dip Strips Dip strips provide the highest sensitivity and the most accurate quantification of peroxide concentration for routine testing. Furthermore, they are easier, faster, and safer to use than other methods, and they detect a wider range of peroxides than other methods. They are, however, somewhat inconvenient to use for testing nonvolatile solvents, and they have a limited shelf life after the container is opened. Repeated cooling and heating cause condensation that will ruin the strips. Storage under dry, inert atmosphere will prolong the shelf life The dip strip method has the advantage of being the most gentle test, an important consideration if the chemical is shock sensitive. It also has another substantial advantage: It can detect, to some extent, dialkyl peroxide, polyperoxides, and cyclic peroxides, compounds that are not efficiently detected by other methods (except, perhaps, the titanium sulfate method) (NOTE: Literature from E. Merck indicates that their test strips will detect hydroperoxides and most higher peroxides, but some polyperoxides may be poorly detected E. Merck and Aldrich Chemical companies make dip strips for the semi-quantitative detection of peroxides in aqueous solutions and organic solvents. The strip incorporates the enzyme peroxidase, which transfers oxygen from peroxide to an incorporated organic redox indicator. The indicator turns blue in the presence of peroxides. The Quantofix Peroxide 100, which has a range of 1-100 mg/l is recommended. Procedures for use are as follows: For volatile organic chemicals: 1. Dip the test strip in the chemical for 1 second, so that the reaction zone is completely wetted. 2. Move the test strip to and fro until solvent has evaporated from the reaction zone. a. dip into distilled water for 1 second, shake off excess water