17th International Mass Spectrometry Conference :: Prague, 2006
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|Session:||Drug Discovery and Development|
|Presentation date:||Tue, Aug 29, 2006|
|Presentation time:||14:30 – 16:00|
Gerard Hopfgartner1,3, Emmanuel Bourgogne1,3, Emmanuel Varesio1,3, Jay Corr2, Jean-Francois Alary21 University of Geneva, Geneva, Switzerland
Correspondence address: Gerard Hopfgartner, University of Geneva, School of Pharmaceutical Sciences, Life Sciences Mass Spectrometry, Bd d'Yvoy 20, Geneva, CH-1211 Switzerland.
Keywords: MALDI; Mass Spectrometry, Quadrupole; Pharmaceutical; Quantitative Analysis.
Novel aspect: New approach for quantitative analysis of low molecular weight compounds in biological matrices with an experimental MALDI source on a triple quadrupole mass spectrometer.
Quantification of low molecular weight (LMW) compounds in biological matrices is mainly performed by liquid chromatography coupled to atmospheric pressure tandem mass spectrometry (LC-MS/MS). Run cycle times are typically in the range of 1 to 5 minutes allowing the analysis of several hundred samples on a daily basis. LC-MS/MS analysis times of 10 seconds have been validated but remains challenging form a sensitivity and robustness point of view. On-line LC-MS has an intrinsic limitation that multiplexing is limited to n= 4-8. Ultra-rapid analysis is not only desirable for high-throughput but also offer unique opportunities for multi-components analysis of small batches of samples. Matrix-assisted laser desorption (MALDI) combined with time-of-flight (TOF) mass spectrometry is widely used for the analysis of proteins and peptides and its potential for the analysis of LMW compounds has also been shown. With high repetition laser, the analysis of one spot can be performed within a few seconds offering really high-throughput capability. Because MALDI requires a matrix for ionization its coupling with separations techniques remains difficult. On the other hand decoupling of sample preparation and separations from MS analysis allows multiplexing approaches.
In the present work, an experimental MALDI source equipped with a high repetition laser was mounted on a triple quadrupole instrument (MALDI-QqQ) and its potential for quantitative bionalysis was investigated. With biological matrices samples preparation remains a very important step to obtain accurate and precise data. Several assays for the determination of pharmaceutical compounds in plasma or urine down to the pg/ml range were developed and validated using in the selected reaction monitoring mode (SRM). For compounds were no metabolites did interfere with the parent compound the chromatographic step could be completely omitted. For those compounds where chromatographic separation remains mandatory automated column-switching approaches were applied. A key advantage of MALDI-QqQ is that sample preparation is completely decoupled from sample analysis and can even be performed on a different location. Also MS re-analysis of selected samples at different conditions is possible. MALDI being a different ionization technique than electrospray, particular attention was given in the study of matrix suppression effects. LC-SRM/MS approaches and opens new doors in the use of mass spectrometric detection for very high-throughput screening.