Leo Wang and William C. Schnute. Mass Spectrometry Technical Center, Dionex Corporation, 1214 Oakmead Parkway, Sunnyvale, CA 94087
Organic acids, especially low molecular mass organic acids (LMMOAs), play crucial roles in plant life, and are associated with fundamental functionalities including energy production, metals absorption, and plant tolerance to environmental stress, supported by increasing experimental evidences. Their importance was recently discovered in biofuel conversion that they account for 7~ 21% dry weight of aqueous extractives from corn stover, and they were also discovered of their inhibitory effects for bioconversion efficiency to ethanol from lignocelluloses. To better understand and optimize the biofuel conversion process, it is paramount to monitor LMMOA in biofuel production.Chromatographic methods with various detection techniques provide the most thorough information to profile and monitor LMMOA. Many reported methods focus on limited number of LMMOAs and are incapable of providing a complete LMMOA profile. This paper describes an ion chromatography mass spectrometric method for profiling analysis of LMMOAs in biomass. 32 LMMOAs were successfully separated and detected. Coefficient of determination greater than 0.99 was achieved for all analytes through the range from low ppb to 2000 ppb (MS/MS) or 5000 ppb (MS). Sensitive MS detection ensures the detection limit reaches to low ppb level except for formic and acetic acid. This method has been applied for analyzing biomass samples obtained from biofuel production process. Seventeen LMMOAs were confirmed of their presence in biomass. Succinic acid presented as the most prominent LMMOA with concentration greater than 200 ppm. Mucic acid, α-ketoglutaric acid, oxalic acid and citric acid also presented at large amount (> 5 ppm).
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