Evaluation of the Oxidation of Rice Husks with Sodium Hypochlorite Using Gas Chromatography-Mass Spectrometry and Direct Analysis in Real Time-Mass Spectrometry

Abstract

Rice husk powder was oxidized in aqueous sodium hypochlorite solution under mild conditions with different reaction times. Fourier transform infrared spectroscopy, gas chromatography-mass spectrometry (GC-MS), and direct analysis in real time-mass spectrometry (DART-MS) were used to analyze the oxidation products. Results showed that oxidation was a feasible way to depolymerize the macromolecules in the biomass and convert hydroxyl groups to carboxyl groups. In total, 113 organic compounds in oxidation products with molecular mass less than 500 Da were identified using GC-MS. As an ambient ionization technique, DART-MS was applied to the determination of biomass derivatives and revealed mass distribution and molecular structure information for the rice husk oxidation products.

Keywords:

• Aqueous sodium hypochlorite solution
• Direct analysis in real time mass spectrometry
• Gas chromatograph-mass spectrometry
• Oxidation
• Rice husk

Acknowledgments

This work was supported by the Fund from Natural Science Foundation of China for Innovative Research Group (Grant 51221462), the Major State Basic Research Development Program of China (Grant 2012CB215302), the National Natural Science Foundation of China (Grant 21206187 and 21206188), and the China Postdoctoral Science Foundation funded projects (2011M500975, 2012T50501, and 2012M511819). Jiangsu Provincial Natural Science Foundation (Grant BK2011225 and BK2011213), the Program of the University in Jiangsu Province for Graduate Student's Innovation in Science Research (Project CXZZ11_0302), the Priority Academic Program Development of Jiangsu Higher Education Institutions, the Fundamental Research Funds for the Central Universities (China University of Mining and Technology; Grant 2011QNA22 and 2011QN23), and the Fund from Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation (East China Institute of Technology; Grant JXMS201101). We would like to acknowledge ASPEC Technologies Limited for loaning the DART 100S system and Dr. Charles C. Liu for his thoughtful discussions.

Notes

^a daf, dry and ash-free base; M _ad, moisture (air dried base); A _d, ash (dry base, i.e., moisture-free base); VM _daf, volatile matter (dry and ash-free base).

DCDE, dimethyl (2E)-2-chloro-3-(dichloromethyl)but-2-enedioate.

DMOPD, 5-(3,4-dimethoxybenzyl)pyrimidine-2,4-diamine.

MODYP, methyl 5-(5-oxotetrahydrofuran-2-yl) pentanoate.