QUALITY-CONTROL OF PHARMACEUTICALS CONTAINING CLENBUTEROL BY THERMAL LENS SPECTROMETRY

An ultrasensitive absorptiometric procedure for the determination of c lenbuterol in pharmaceutical preparations was developed. Clenbuterol w as diazotized with nitrite and coupled with 1-(naphthyl)ethylenediamin e, and the absorbance of the azo dye formed was measured by both spect rophotometry and ultrasensitive thermal lens spectrometry (TLS). The T LS limit of detection was 1.5 ppb, 14-fold lower than with a Hewlett-P ackard diode array spectrophotometer. Thus, the TLS procedure can be a dvantageously applied to quality control of clenbuterol at the individ ual dose level and in small samples. Repeatability as relative standar d deviation was 1.5% (50 ppb, n = 6).