A simple method is described for monitoring nitrogen oxides over a period between one week and a month. The method is based on a piece of chromatographic paper, impregnated with diphenylamine, which is fixed onto a candle and exposed to the air. The nitrogen oxides in the air react with amine to form nitrosamine which is then extracted from the paper and determined by the usual laboratory methods. The results derived from this summation method correlate very well with those obtained from more sophisticated methods such as chemiluminescence.
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