CAPILLARY GAS-CHROMATOGRAPHIC ASSAY OF CAMPHOR AND M-CRESOL IN DERMATOLOGICAL CREAMS

Camphor and m-cresol mixtures are used in antiseptic and anti-itching creams. No compendial method exists for these preparations. This paper reports a capillary gas chromatographic method using FID detection wi th 2,6-di-tert-butyl-4-methylphenol as internal standard on a 30 m x 0 .32 mm Supelcowax(R)-10 column (0.25 mu m film) with helium as carrier gas. Ramped temperature programming was applied. The method allows si multaneous quantitation of camphor and m-cresol in the presence of o- and p-cresols, calamine and zinc oxide. Overall percent recoveries (+/ - SD n = 9) of camphor, o-, p- and m-cresol from spiked placebo creams , at a labeled amount of 10 (w/w)% were 96.9 +/- 0.6, 98.2 +/- 0.6, 99 .2 +/- 0.5 and 101.0 +/- 0.9%, respectively, and at a labeled amount o f 1% were 96.7 +/- 0.6, 97.8 +/- 0.9, 97.8 +/- 0.6, and 100.3 +/- 1.0% , respectively. The recovery studies were carried out at +/- 30% of th e labeled amounts. Linear peak area or height ratios were obtained (r > 0.999) for camphor, o-, p- and m-cresol covering a concentration ran ge of 10-200% of the labeled amount. Linearity (I > 0.999) was also ob tained for nz-cresol when the relative concentration of o- and p-creso l was varied from 5 to 100% of the m-cresol concentration. The resolut ion between the 'critical pair' of p- and m-cresol was greater than or equal to 1.1. The limit of quantitation was 23 pg for In-cresol and 9 .3 pg for camphor using an injection split of 1:50. The repeatability (%RSD) for all compounds were < 2% for peak area and < 1.4% for peak h eight ratios. System suitability and robustness of the method were est ablished. The method was successively applied to the assay of availabl e commercial products and allows assay of camphor and the three cresol isomers. (C) 1998 Elsevier Science B.V. All rights reserved.