Determination of fluoride impurities in Leuprolide. Comparison of analytical methods

Fluoride impurities were determined in technical samples of Leuprolide (ant i-cancer drug for prosthetic cancer) using reverse-phase liquid chromatogra phy and derivative spectrophotometry. The chromatographic method was based on the ternary fluoride complex with zirconium(IV) and 2-(5-bromo-2-pyridyl azo)-5-diethylaminophenol (5-Br-PADAP). The analysis was performed on a Nuc leosil C-18 column with LiChrosphere RP-100 end-capped phase, using as elue nt acetonitrile (85%v/v) water mixture at pH 4.1 +/- 0.2. Fluoride content was determined with;se of the method of standard additions (MOSA) as 2.34 m g g(-1) and 0.29 mg g(-1) in two different samples. A spectrophotometric de termination has been carried out by La(III)-F--ALC [ternary complex La(III) -F--alizarin complexone] method with using third derivative spectrophotomet ry. By this method fluoride content was determined as 1.99 mg g(-1) and 0.3 4 mg g(-1) in the samples previously analyzed chromatographically. A valida tion for both (i.e. chromatographic and spectrophotometric) methods was per formed. Statistical analysis showed that spectrophotometric methods could n ot be used for quantitative determination of fluoride in samples containing them in concentration less than 0.5 mg g(-1). (C) 2000 Elsevier Science B. V. All rights reserved.