A test method is described for the verification of proper use concentrations of solutions of straight quaternary ammonium rinses or formulated detergent-quaternary preparations. The simple test kit and direct procedure afford an economical and easily used test method for the sanitarian and the food and beverage worker. The estimation of the quaternary concentration is accomplished by the reaction of the quaternary with a definite amount of bromphenol blue accurately buffered on the acid side. The blue color of the dye-quaternary complex is dominant if 200 ppm. or more of quaternary is present in the solution. If less than 200 ppm. quaternary is present various shades of green are produced by the partial conversion of the dye to its blue complex plus the acidified yellow excess. The test reagent may be used with many proprietary preparations after the dye demand of the specific quaternary at the recommended use concentration is established.

The test described is simpler than related methods in eliminating use of an organic solvent and in its wide adaptability to service conditions. It is simple and accurate and economical enough to encourage greater use of controlled solutions.

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Author notes

Mr. Dwight B. Conklin has been a staff member of the Bacteriological Section of the Research and Development Division of Wyandotte Chemicals Corporation since 1945. He received a Master of Arts degree from Syracuse University where he also served as an instructor in bacteriology. Before going into industry he spent two years as a research assistant in plant biology at the State University of Iowa.