Direct analysis of samples under ambient condition by high-voltage-assisted laser desorption ionization mass spectrometry in both positive and negative ion mode

Authors

  • Xinxin Ren,

    1. Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, China
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  • Jia Liu,

    1. Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, China
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  • Chengsen Zhang,

    1. Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, China
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  • Hai Luo

    Corresponding author
    • Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, China
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Correspondence to: H. Luo, Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China.

E-mail: hluo@pku.edu.cn

Abstract

RATIONALE

With the rapid development of ambient mass spectrometry, the hybrid laser-based ambient ionization methods which can generate multiply charged ions of large biomolecules and also characterize small molecules with good signal-to-noise in both positive and negative ion modes are of particular interest.

METHODS

An ambient ionization method termed high-voltage-assisted laser desorption ionization (HALDI) is developed, in which a 1064 nm laser is used to desorb various liquid samples from the sample target biased at a high potential without the need for an organic matrix. The pre-charged liquid samples are desorbed by the laser to form small charged droplets which may undergo an electrospray-like ionization process to produce multiply charged ions of large biomolecules.

RESULTS

Various samples including proteins, oligonucleotides (ODNs), drugs, whole milk and chicken eggs have been analyzed by HALDI-MS in both positive and negative ion mode with little or no sample preparation. In addition, HALDI can generate intense signals with better signal-to-noise in negative ion mode than laser desorption spay post-ionization (LDSPI) from the same samples, such as ODNs and some carboxylic-group-containing small drug molecules.

CONCLUSIONS

HALDI-MS can directly analyze a variety of liquid samples including proteins, ODNs, pharmaceuticals and biological fluids in both positive and negative ion mode without the use of an organic matrix. This technique may be further developed into a useful tool for rapid analysis in many different fields such as pharmaceutical, food, and biological sciences. Copyright © 2013 John Wiley & Sons, Ltd.

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