Quantification of ropivacaine and its major metabolites in human urine samples utilizing microextraction in a packed syringe automated with liquid chromatography-tandem mass spectrometry (MEPS-LC-MS/MS).

The determination of ropivacaine and its major metabolites in urine was performed using microextraction in a packed syringe as an on-line sample preparation method with LC and MS/MS. The sampling sorbent utilized was polystyrene polymer. [2H7]ropivacaine was used as the internal standard. The lower LOQ was 5.0 nmol/L. The calibration curves were obtained within the concentration range 5-2000 nmol/ L in urine. The regression correlation coefficients for urine samples were > or = 0.999 for all runs. The between-batch accuracy and precision values were determined from six replicates of quality control (QC) samples at three different concentrations in human urine. The mean accuracy values for the QC samples, reported as the percentage difference from the nominal value, were in the range of 99-115%. The precisions, given as the RSDs, were in the range 1.9-11%. The present method is miniaturized and fully automated and can be used for pharmacokinetic and pharmacodynamic studies.