Switching-valve--filter technique for the direct injection and analysis of drugs in plasma using high-performance liquid chromatography.
An automated technique involving switching valves and a filter assembly has been developed and evaluated for the on-line precipitation of proteins and peptides from plasma samples. In the set-up, the proteins were precipitated on-line by injecting the plasma sample into a stream of organic precipitating agent. The precipitates so formed are filtered on-line by a set of filter assemblies consisting of ordinary in-line HPLC solvent filters. Evaluation of the technique was performed using ibuprofen and a mixture of three estrogens, estradiol, equilin and estrone, spiked in dog plasma. The coefficients of variation (C.V.) for system suitability parameters were below 10%. Absolute recovery of ibuprofen in plasma ranged from 80% for 100 micrograms/ml to 114% for 5 micrograms/ml spiked concentrations, respectively. Resolution for equilin and estrone, two closely eluting peaks, was 1.79 (C.V. = 5.8%, n = 7). The switching-valve--filter assembly had no significant effect on the efficiency of the HPLC system.
Generic Drugs Research, OGD, CDER, FDA, Washington, DC 20204.
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D000818:Animals; D001322:Autoanalysis; D002851:Chromatography, High Pressure Liquid; D004285:Dogs; D004967:Estrogens / Q000097:blood; D005069:Evaluation Studies as Topic; D007052:Ibuprofen / Q000097:blood; D007202:Indicators and Reagents; D004364:Pharmaceutical Preparations / Q000032:analysis*; D010949:Plasma / Q000737:chemistry*
D004967:Estrogens; D007202:Indicators and Reagents; D004364:Pharmaceutical Preparations; D007052:Ibuprofen