Determination of p-chloronitrobenzene in plasma by reversed-phase high-performance liquid chromatography

A simple, accurate and precise isocratic reversed-phase high-performance liquid chromatographic method was developed and validated for the determination of p-chloronitrobenzene (p-CNB) in rat plasma. A plasma sample was deproteinized with methanol containing the internal standard (p-bromonitrobenzene). The resulting methanol eluate obtained after centrifugation was filtered and injected into a high-performance liquid chromatograph (50 microliters each). A column packed with 5 microns octadecylsilane (ODS) spherical particles was used with isocratic elution of methanol-water (45:55, v/v) at a flow-rate of 1.0 ml/min. The compounds were detected by ultraviolet absorbance at 280 nm. The retention times of p-CNB and the internal standard were 12.5 and 15.5 min, respectively, at a column oven temperature of 30 degrees C. The results were linear from 0.05 to 100 micrograms/ml (r = 0.999), and the detection limit was 0.01 microgram/ml. The relative error and the coefficient of variation on replicate assays were less than 7 and 10%, respectively, for all concentrations studied. The overall recoveries of p-CNB were between 97 and 105%. Plasma samples could be stored for up to one month at -20 degrees C.