DETERMINATION OF DIHYDROSTREPTOMYCIN SULFATE IN MILK BY HPLC USING ION-PAIR AND POSTCOLUMN DERIVATIZATION

An isocratic, paired-ion reversed-phase high-performance liquid chroma tographic method for the determination of dihydrostreptomycin sulfate in milk by postcolumn derivatization has been developed. The milk was treated with 85% trichloroacetic acid to precipitate proteins, and the supernatant clean-up was performed using a tC18 pretreatment column. The correlation coefficients were 0.999. The lower limit of quantifica tion was 25 ng/ml and the limit of detection close to 15 ng/ml. The re covery of dihydrostreptomycin sulfate varying from 82.6 to 82.8%.