Determination of Ketorolac in Human Plasma by High Performance Liquid Chromatography After Automated On-Line Solid Phase Extraction

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Abstract
An automated solid phase extraction-based procedure for the determination of ketorolac in human plasma was developed and validated. Solid phase extraction of ketorolac tromethamine and ketoprofen (internal standard) was performed on disposable C-18 cartridges directly from plasma samples spiked with the corresponding standards after dilution with saline. All operations were performed automatically by means of a switching-valve assembly in the sample preparation module (Prospekt system), and sample analysis were carried out by on line connection with the HPLC system. Linearity of the analytical methodology was assessed at the concentration range 25–2500 ng/mL ketorolac tromethamine. However, accurate and precise determinations at 5 and 10 ng/mL were obtained by the use of weighing in calibration curve fitting. The mean absolute recoveries for ketorolac tromethamine and the internal standard were 87.7% and 72.9% respectively. Respective intra- and inter-assay precision values were below 7.2 and 18.0%, the later at the 5 ng/mL concentration level of ketorolac tromethamine which was considered as the lower limit of quantitation (3.4 ng/mL in terms of free acid form). Intra- and inter-assay accuracy, expressed as relative error in percentage, were less than 9.5 and 8.8% respectively. The minimal sample handling and the obtained precision and accuracy at the wide range of concentration levels tested make this method suitable for routine quantitations of ketorolac in human plasma.