Dual Electrospray Ionization Source for Confident Generation of Accurate Mass Tags Using Liquid Chromatography Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

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• 作者：Angelito I. Nepomuceno ; David C. Muddiman ; H. Robert Bergen ; III ; James R. Craighead ; Michael J. Burke ; Patrick E. Caskey ; and Jonathan A. Allan
• 刊名：Analytical Chemistry
• 出版年：2003
• 出版时间：July 15, 2003
• 年：2003
• 卷：75
• 期：14
• 页码：3411 - 3418
• 全文大小：154K
• 年卷期：v.75,no.14(July 15, 2003)
• ISSN：1520-6882

文摘

Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) has rapidly established a prominentrole in proteomics because of its unparalleled resolvingpower, sensitivity and ability to achieve high mass measurement accuracy (MMA) simultaneously. However,space-charge effects must be quantitatively, routinely, andconfidently corrected because they are known to profoundly influence MMA. We argue that the most effectiveway to account for space-charge effects is to introduce aninternal mass calibrant (IMC) using a dual electrosprayionization (ESI) source where the IMC is added from aseparate ESI emitter. The major disadvantage of our initialdual ESI source to achieve high MMA, and arguably theonly one, was the time required to switch between theanalyte emitter and IMC emitter (i.e., >300 ms). Whilethis "switching time" was acceptable for direct infusionexperiments, it did not lend itself to high-throughputapplications or when conducting on-line liquid separations. In this report, we completely redesigned the dualESI source and demonstrate several key attributes. First,the new design allows for facile alignment of ESI emitters,undetectable vibration, and the ability to extend to multiple emitters. Second, the switching time was reducedto <50 ms, which allowed the analyte and IMC to beaccumulated "simultaneously" in the external ion reservoir and injected as a single ion packet into the ioncyclotron resonance cell, eliminating the need for aseparate accumulation and ion injection event for the IMC.Third, by using a high concentration of the IMC, theresidence time on this emitter could be reduced to ~80ms, allowing for more time spent accumulating analyteions of significantly lower concentration. Fourth, multiplexed on-line separations can be carried out providingincreased throughput. Specifically, the new dual ESIsource has demonstrated its ability to produce a stableion current over a 45-min time period at 7 T resulting inmass accuracies of 1.08 ppm ± 0.11 ppm (mean ±confidence interval of the mean at 95% confidence; N =160). In addition, the analysis of a tryptic digest ofapomyoglobin by nanoLC-dual ESI-FT-ICR afforded anaverage MMA of -1.09 versus -74.5 ppm for externallycalibrated data. Furthermore, we demonstrate that theamplitude of a peptide being electrosprayed at 25 nM canbe linearly increased, ultimately allowing for dynamicanalyte/IMC abundance modulation. Finally, we demonstrate that this source can reliably be used for multiplexingmeasurements from two (eventually more) flow streams.