Quantitative determination of piritramide in human serum applying liquid chromatography-two-stage mass spectrometry

A method for the determination of the synthetic narcotic analgesic piritramide in human serum utilizing high-performance liquid chromatography with atmospheric pressure chemical ionization two-stage mass spectrometry (HPLC-APCI-MS-MS) is presented. Pipamperone is used as the internal standard. Serum samples are prepared by liquid-liquid extraction under basic conditions with 1-chlorobutane. The chromatographic separation is achieved on an RP-18 stationary phase applying gradient elution with methanol-0.02% trifluoroacetic acid in water. Detection is carried out in the MS-MS single reaction monitoring mode of the ion-trap mass spectrometer. The limit of detection is 0.3 ng/ml and the calibration covers the range of 1-80 ng/ml. The intra-day RSDs are 6.1 to 7.3% over the calibration range, whereas the inter-day RSDs are 9.6 to 12.8%.