Coupling device for desorption of drugs from solid-phase extraction-pipette tips and on-line gas chromatographic analysis

Solid-phase extraction-pipette tips were used for micro solid-phase extract ion of lidocaine and diazepam. Off-line desorption was done after in-vial c ollection for reference purposes, whereas with on-line desorption the eluat e was directly introduced in the gas chromatograph. With both methods the t otal eluate (100 mu l) was introduced into the GC system, which was equippe d with a programmed-temperature vaporiser (PTV) for large volume injection. For on-line desorption a laboratory-made coupling device was developed to connect the pipette tips with the injector of the PTV. The coupling device was applied successfully since no leakage occurred at the connection of the coupling device and the pipette tip. No significant differences in recover y of lidocaine and diazepam and in presence of impurities were observed bet ween chromatograms obtained with either off-line or on-line desorption. Pre liminary experiments with standard solutions showed recoveries of about 75% for a concentration level of 1 mu g/ml. The system seems particularly suit able for high-throughput analysis. (C) 1999 Published by Elsevier Science B .V. All rights reserved.