Effects of phenylbutazone and oxyphenbutazone on basic drug detection in high performance thin layer chromatographic systems*,†

Abstract

Interference or masking in TLC occurs when the presence of one drug on a TLC plate physically obscures or interferes with the detection of another drug. The ability of phenylbutazone and oxyphenbutazone to make or interfere with the detection by high performance thin layer chromatography (HPTLC) of basic drugs used illegally in horse racing. Of fifty-five basic drugs called positive since 1981 by laboratories affiliated with the Association of Official Racing Chemists (AORC), 40 did not comigrate with phenylbutazone or oxyphenbutazone and could not, be masked. When 75 .mu.g/ml of oxyphenbutazone was spiked into urine samples, subjected to an extraction procedure for basic drugs, and then run in routine HPTLC systems, no spots due to oxyphenbutazone appeared. Masking by oxyphenbutazone, therfore, did not and could not occur in this test systems. When phenylbutazone at a concentration of 30 .mu.g/ml was spiked into urine samples and run in the routine HPTLC system, phenylbutazone spots were visible under ultraviolet light and after certain specific oversprays were used to visualize basic drugs. These spots did not interfere with routine thin layer testing for basic drugs. Apparently, phenylbutazone and oxyphenbutazone had no significant ability to interfere with detection of the parent forms of these basic drugs under the conditions described in these experiments.