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Sensitive ionization of non‐volatile analytes using protein solutions as spray liquid in desorption electrospray ionization mass spectrometry
Author(s) -
Zhu Zhiqiang,
Han Jing,
Zhang Yan,
Zhou Yafei,
Xu Ning,
Zhang Bo,
Gu Haiwei,
Chen Huanwen
Publication year - 2012
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.6387
Subject(s) - chemistry , desorption electrospray ionization , mass spectrometry , extractive electrospray ionization , chromatography , electrospray ionization , analyte , ambient ionization , analytical chemistry (journal) , detection limit , desorption , acetic acid , electrospray , ionization , chemical ionization , sample preparation in mass spectrometry , ion , organic chemistry , adsorption
RATIONALE Desorption electrospray ionization (DESI) is the most popular ambient ionization technique for direct analysis of complex samples without sample pretreatment. However, for many applications, especially for trace analysis, it is of interest to improve the sensitivity of DESI‐mass spectrometry (MS). METHODS In traditional DESI‐MS, a mixture of methanol/water/acetic acid is usually used to generate the primary ions. In this article, dilute protein solutions were electrosprayed in the DESI method to create multiply charged primary ions for the desorption ionization of trace analytes on various surfaces (e.g., filter paper, glass, Al‐foil) without any sample pretreatment. The analyte ions were then detected and structurally characterized using a LTQ XL mass spectrometer. RESULTS Compared with the methanol/water/acetic acid (49:49:2, v/v/v) solution, protein solutions significantly increased the signal levels of non‐volatile compounds such as benzoic acid, TNT, o ‐toluidine, peptide and insulin in either positive or negative ion detection mode. For all the analytes tested, the limits of detection (LODs) were reduced to about half of the original values which were obtained using traditional DESI. The results showed that the signal enhancement is highly correlated with the molecular weight of the proteins and the selected solid surfaces. CONCLUSIONS The proposed DESI method is a universal strategy for rapid and sensitive detection of trace amounts of strongly bound and/or non‐volatile analytes, including explosives, peptides, and proteins. The results indicate that the sensitivity of DESI can be further improved by selecting larger proteins and appropriate solid surfaces. Copyright © 2012 John Wiley & Sons, Ltd.