Determination of MDL 201,012 at femtomole/millilitre levels in human plasma by liquid chromatography with electrochemical detection

A sensitive and selective liquid chromatographic method to quantitate MDL 201,012 in human plasma was developed and validated. MDL 201,012 (I), diethyl‐MDL 201,012 (internal standard, II) and desmethyldiol‐MDL 201,012 (masking agent, III) were isolated from basified plasma (2 mL) by solid phase extraction using Bond‐Elut® C‐18 cartridges. Endogenous components were selectively removed prior to eluting the analytes from the sorbent. Components were separated using on‐line LC column switching with a cyanopropyl precolumn and a phenyl analytical column. The analytical column effluent was monitored electrochemically at a glassy carbon electrode at a potential of + 1025 mV vs. Ag/AgCI. Peak‐height ratios were proportional to the amount of MDL 201,012 added to plasma over the range 125–7500 pg/mL MDL 201,012. Absolute recovery of MDL 201,012 from human plasma was >94% across the calibration range. The minimum quantitation limit was 125 pg/mL. Assay precision (%RSD) ranged from 5.2 to 13% based on the analysis of quality control standards containing 125, 250, 500, 1000, 2500, 5000 and 7500 pg/mL MDL 201,012. Corresponding assay accuracy (% relative error) was ±8.5%. The method has been successfully used to quantitate MDL 201,012 in samples from acute dose tolerance studies in human volunteers.