Quasi-linear gradients for capillary liquid chromatography with mass and tandem mass spectrometry

Gradient elution, capillary liquid chromatography mass spectrometry was per formed with linear, static gradients constructed by laminar flowing ten, 1. 5 mu L volume steps of decreasing organic concentration into tubing of smal l internal diameter. Sample loading, gradient formation, and sample elution were accomplished entirely by means of a commercially available micro-auto sampler and single-syringe drive pump. The procedure was simple, fast, stab le, and reproducible. Essentially linear gradients were produced without th e use of additional valves, mixers, pumps or software. It took less than 10 minutes to form a gradient and less than 30 minutes to construct the set o f individual buffer vials. The gradients were shown to be stable to storage . One hour after forming, peak retention times were reproduced to +/-0.5%. Long-term retention time reproducibility was found to vary by +/-2%, Chroma tographic resolution was comparable or superior to that obtained by gradien t elution with conventional dynamic mixing and split how, The procedure was adapted with a 'peak parking' method which extended the t ime for generating peptide fragmentation data up to 10 minutes per peptide with the triple quadruple mass spectrometer, Using this technique, collisio n data were collected at the 25 femtomole level on nine of ten tryptic pept ides in a single run. Copyright (C) 2000 John Whey & Sons, Ltd.