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Anal Chem. 2012 Jul 17;84(14):6116-21. doi: 10.1021/ac300926h. Epub 2012 Jun 27.

Quantitative multiple reaction monitoring of peptide abundance introduced via a capillary zone electrophoresis-electrospray interface.

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Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States.


We demonstrate the use of capillary zone electrophoresis with an electrokinetic sheath-flow electrospray interface coupled to a triple-quadrupole mass spectrometer for the accurate and precise quantification of Leu-enkephalin in a complex mixture using multiple-reaction monitoring (MRM). Assay time is <6 min, with no re-equilibration required between runs. A standard curve of Leu-enkephalin was performed in the presence of a background tryptic digest of bovine albumin. We demonstrate reasonably reproducible peak heights (21% relative standard deviation), retention times (better than 1% relative standard deviation), and robust electrospray quality. Our limit of detection (3σ) was 60 pM, which corresponds to the injection of 335 zmol of peptide. This is a 10-20-fold improvement in mass sensitivity than we have obtained by nano HPLC/MRM and substantially better than reported for LC/MS/MS. Further quantification was performed in the presence of stable-isotope-labeled versions of the peptides; under these conditions, linearity was observed across nearly 4 orders of magnitude. The concentration detection limit was 240 pM for the stable-isotope-labeled quantification.

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