[Chlorine covers on skin surfaces. I. Determination of the covering strength with the DPD cuvette method]

A new photometric micro method for the quantitative determination of "chlorine covers" on skin surfaces is presented. It is based on the formation of the dye emerging from the reaction of the bound chlorine with iodide and diethyl-p-phenylene diamine (DPD). In contrast to the already described "glove-method" (Hyg. + Med. 13 (1988) 157) it can be applied to all regions of the body and enables a valuation of the specific chlorine cover (micrograms Cl2/cm2). Further features of the method are a small demand of time and work, and--on grounds of the high sensitivity--only a small measuring area (approximately 1.5 cm2) which allows repeated measurements for improving the statistical safety. However, since the different skin areas take up variable amounts of chlorine this can be done only at limited areas. Founded upon a comprehensive error analysis a precision (calculated variation coefficient) of +/- 3-4% for flat and +/- 8-9% for curved (finger tips) skin areas with not too small chlorine covers (greater than 0.3 microgram Cl2/cm2) has been evaluated. Failing a reference method resp. standard areas with known chlorine covers the accuracy of the method could not exactly be ascertained. Owing to an estimation of the most important systematic errors the method might yield results slightly to low (deviation from the true value: approximately -5 to -10%). In spite of this restriction the DPD-cuvette-method is a very useful analytical procedure and the chlorine cover measured herewith and expressed as microgram Cl2/cm2 represents a new skin related parameter, which not only allows an estimation of persistent bactericidal effects on skin surfaces, but also might be useful as an indicator for the roughness of the skin.