DETERMINATION OF SPIRAMYCIN AND NEOSPIRAMYCIN IN PLASMA AND MILK OF LACTATING COWS BY REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

After chloroform extraction, the rapid and sensitive determination of spiramycin and neospiramycin can be performed with AASP-diol clean-up cartridges prior to reversed-phase C-18 high-performance liquid chroma tography. The limits of quantification of spiramycin in plasma and mil k are 0.023 and 0.013 mu g/ml, respectively, and those of neospiramyci n, are 0.058 and 0.006 mu g/ml, respectively. Application of the metho d to the analysis of plasma and milk samples obtained from pharmacokin etic studies is described. Spiramycin has a terminal half-life of 14.2 7 h in plasma and 34.59 h in milk, while neospiramycin has a half-life of 25.62 h in plasma and 105.85 h in milk.