A novel method has been developed for the rapid solid phase extraction of drugs and metabolites from biological fluids, prior to further analysis. The newly designed, 96-tube micropreparation block facilitates high throughput by enabling the extraction of 96 samples simultaneously. The system is described, linked to HPLC/APCI-MS/MS, for the determination of darifenacin in human plasma. The resulting procedure, using deuterated darifenacin as internal standard, is validated over the concentration range 25-2000 pg/mliter; accuracy (0.6-4.6%) and precision (3.6-18.8%) are considered acceptable and overall recovery was determined to be approximately 50%.

A molecularly imprinted polymer has been developed which subsequently demonstrated an ability to selectively retain darifenacin (UK-88,525-S) from aqueous acetonitrile when used as a stationary phase in HPLC columns and as a packing in solid-phase extraction cartridges. The imprinted polymer is applicable to a wide range of analytical methods including extraction from plasma, purification ofradiolabelled UK-88,525, chiral separations and separation of metabolites and structural analogues. The polymer is able to extract darifenacin directly from a protein-precipitated human plasma/ acetonitrile (1:1 v/v) mixture with 100 % recovery. The imprinted polymer can also effect a repurification of 14C-labelled darifenacin. The drawbacks of molecular imprints for ultra-trace bioanalysis (in the sub-nanogram/mL range) are discussed. These centre on the difficulty of removing all the template from the polymer and the consequent effects of template bleed on assay precision and accuracy when used as solid-phase extraction cartridges. Possible solutions to this problem are considered. 0.~. NH2~"'~,, 0 9 ) 9 indicates a chiral centre Figure 1 Structure of darifenacin

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Turbulent flow chromatography coupled to tandem mass spectrometry (TFC-MS-MS) has recently emerged as a potentially fast, sensitive and specific technique for the direct analysis of pharmaceutical compounds from crude plasma. TFC-MS-MS removes the need for time-consuming sample preparation procedures such as solid-phase extraction (SPE) or liquid-liquid extraction (LLE). A relatively high flow rate combined with the use of an HPLC column with large porous particles allows the on-line clean up and quantification of compounds in plasma samples. Until now, the amount of plasma directly injected into TFC systems has rarely exceeded 30 IxL in order to prevent rapid column degradation. Increasing the injection volume also induces high carry-over levels, particularly fordrugs with basic and/or hpophilic properties. This paper describes the first generic TFC-MS-MS method developed in a 96-well format, which allows the direct injection of 200 I~L of 1:1 diluted plasma (equivalent to 100 I~L neat plasma). An average of 390 injections was carried out with each extraction column. More than 2000 clog plasma samples were injected into the system without any sign of carryover. The method was fully validated over a 5 -5 0 0 ng mL 1 range for three basic compounds: cloxazosin, CP122,288 and clofetilide. The imprecision was 1.2 to 8.3% for doxazosin, 1.5 to 4% for CP122,288 and 1.6 to 9.2% for dofetilide. The inaccuracy ranged from 6% to 7.9%. This generic methodology was then used to assay l",,vo structurally unrelated development compounds, showing that the method accuracy and sensitivif,/were adequate for the early pharmacokinetic (PK) studies in animals.