Weinfeld R E, Macasieb T C
J Chromatogr. 1979 Sep 11;164(1):73-84. doi: 10.1016/s0378-4347(00)81573-x.
A rapid, sensitive, and specific high-performance liquid chromatographic assay was developed for the determination of trimethoprim in blood, plasma, and urine using normalphase (adsorption) chromatography on a microparticulate silica column and UV monitoring at 280 nm. Trimethoprim is selectively extracted from the biological sample matrix at alkaline pH with chloroform, providng nearly quantitative extraction (greater than 95%) and a sensitivity limit of 0.01 to 0.02 microgram/ml blood or plasma, without interference from sulfonamides.
