RAPID, SPECIFIC AND SENSITIVE METHOD FOR ISONIAZID DETERMINATION IN SERUM

An original simple, specific and rapid high-performance liquid chromat ographic assay for the determination of isoniazid (INH) in human serum is presented. The drug was extracted from the serum by protein precip itation with 30% (w/v) trichloroacetic acid, then the drug was reacted with the coupling reagent, trans-cinnamaldehyde, to form a derivative absorbing at 340 nm. A 20-mu l aliquot was injected into the chromato graph after neutralization with 1 M KOH solution. A liquid chromatogra ph equipped with a reversed-phase 30-mu m C-18 precolumn linked to a 4 -mu m C-18 analytical column was used. The drug was eluted with a mixt ure of acetonitrile-water-triethylamine-acetic acid (400:600:2:1, v/v) , pH value was 5 +/- 1. Flow-rate and wavelength were set at 1 ml/min and 340 nm, respectively. The extraction recoveries from human serum a veraged 100% for INH at concentrations of 1, 2 and 4 mg/l. The coeffic ients of variation for three different concentrations of INH in serum in the within-day study varied between 1.2 and 3.5%, whereas those in the day-to-day study varied between 2.8 and 4.3%.