GAS CHROMATOGRAPHY OF METHYLENE CHLORIDE 123 A R E 2.0 A 1.0 Me CL z/n, - PROPANOL I.O 2D 5.0 WEIGHT Figure 4. Response of detecto,' to methylene chloride relative to n-propanol over range ooe ale, proximately 3 to 20% in hair spray It was observed that samples in the serum bottles could be inverted in a small beaker and held several hours at room temperature without change in composition. Maintaining these samples overnight, either at room temperature or at refrigerator temperature, was not successful. •towever, a series of samples held overnight in a freezer gave identical results when reanalyzed the following day. After 30 or 40 samples were run through the column, a slight distor- tion of the n-propanol peak and deteriorating resolution were observed. This was atributed to a build-up of plasticizer and other higher boiling ingredients in hair spray on the column. Conditioning the column at 200øC for 1/2 hour at the start of a day's run was found to eliminate this problem. There has been no indication as yet of any failure of the column after almost 500 analyses. SUMMARY A new gas chromatographic method for determining methylene chloride in hair sprays in less than 10 min has been developed. The reproducibility of commercial samples containing 7-8% methylene chlo- ride has been shown to be better than --2% relative. Expensive sample equipment or instrument modifications are not required and training of personnel is minimal. (Received October 1, 1971)

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