Determination of trapidil in human serum and urine by derivative UV spectrophotometry after selective solid-phase extraction.

A novel analytical technique able to determine the anti-ischemic drug trapidil in human serum and urine is proposed. In order to achieve satisfactory sensitivity and selectivity, an extraction procedure was required to isolate the drug from complex matrixes such as serum and urine. A solid-phase extraction procedure was investigated to both increase the analyte concentration and eliminate the interfering molecules present in large amounts in both matrixes. Optimization of the extraction step was realized by selecting a new polymeric sorbent based on a surface-modified styrene-divinylbenzene polymer which provided fast and efficient drug extraction. Drug quantification was performed by using the third-order derivative spectra of the SPE eluates. Absorbance specific signals at (3)D(335,316) and (3)D(316) nm for urine and serum, respectively, were demonstrated to be directly proportional to drug concentration and barely affected by residual matrix interferences. Under the optimized experimental conditions the calibration plots were linear over the concentration range 0.2-50 microg mL(-1). The method was validated by analysis of a series of spiked samples. Accuracy (recovery of 95 and 94% for serum and urine, respectively) and precision (RSD below 4%) were good.