Determination of fentanyl in human plasma and fentanyl and norfentanyl in human urine using LC-MS/MS.

Fentanyl, a potent analgesic drug, has traditionally been used intravenously in surgical or diagnostic operations. Formulations with fentanyl in oral transmucosal delivery system and in transdermal depot-patch have also been developed against breakthrough pain in cancer patients. In this report, LC-MS/MS methods to determine fentanyl in human plasma as well as fentanyl and its main metabolite, norfentanyl, in human urine are presented together with validation data. The validation ranges were 0.020-10.0 and 0.100-50.0 ng/ml for fentanyl in plasma and urine, respectively, and 0.102-153 ng/ml for norfentanyl in urine. Liquid-liquid extraction of the compounds fentanyl, norfentanyl and the deuterated internal standards, fentanyl-d5 and norfentanyl-d5 from the matrixes was applied and separation was performed on a reversed phase YMC Pro C18-column followed by MS/MS detection with electrospray in positive mode. The inter-assay precision (CV%) was better than 4.8% for fentanyl in plasma and 6.2% and 4.7% for fentanyl and norfentanyl, respectively, in urine. The ruggedness of the methods, selectivity, recovery, effect of dilution and long-term stability of the analytes in plasma and urine were investigated. Effect of haemolysis and stability of fentanyl in blood samples were also studied. The methods have been applied for the determination of fentanyl in plasma samples and fentanyl/norfentanyl in urine samples taken for pharmacokinetic evaluation after a single intra-venous (i.v.) dose of 75 microg fentanyl.

Enantiomeric separation of basic drugs using N-benzyloxycarbonylglyclyl-L-proline as counter ion in methanol.

Direct separation of enantiomeric amines using mainly N-benzyloxycarbonylglycyl-L-proline (L-ZGP) but also N-benzyloxycarbonylglyclglcyl-L-proline (L-ZGGP) as the chiral counter ion in methanol is described. The solid phase was Hypercarb porous graphitic carbon. Several amines of pharmacological interest (e.g., alprenolol, sotalol, terbutaline, promethazine and trimipramine) were separated with high enantioselectivity (alpha = 1.16-1.98) using L-ZGP and L-ZGGP as chiral selectors. In accordance with ion-pair chromatography, the retention of the enantiomeric amines was found to increase with increasing concentration of the anionic form of L-ZGP. Addition of a base (sodium hydroxide or an alkylamine) in excess of L-ZGP gave rise to a decrease in retention and enantioselectivity. The enantioselective retention was also affected by adding 2-propanol or acetonitrile to the mobile phase.

Enantioselective high-performance liquid chromatographic determination of (SR)- and (RS)-mefloquine in plasma using N-benzyloxycarbonyl-glycyl-L-proline as chiral counter ion.

A stereoselective HPLC method is described for the determination of (SR)- and (RS)-mefloquine in plasma. The direct chiral separation is carried out on a Hypercarb-S column (porous graphitised carbon) with N-benzyloxycarbonyl-glycyl-L-proline (L-ZGP) as a chiral counter-ion in a reversed-phase system. The sample work-up included protein precipitation by addition of zinc sulphate and acetonitrile followed by liquid-liquid extraction with methyl-tert.-butyl ether. After evaporation of the organic phase, the residue is dissolved in the mobile phase and injected onto the column. Analyses of the enantiomers in plasma after a single oral dose of mefloquine indicates that the pharmacokinetics of the two enantiomers are different. The method is validated by determining the absolute recovery, linearity, accuracy, precision and inter- and intra-assay variation.