Confirmation and determination of carboxylic acids in root exudates using LC-ESI-MS

• Published in: Journal of separation science 2007-10, Vol.30 (15), p.2440-2446
• Main Authors: Chen, Zuliang, Jin, Xiaoyin, Wang, Qinqping, Lin, Yuman, Gan, Li, Tang, Caixing
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Carboxylic acids; Chemical constitution; Fundamental and applied biological sciences. Psychology; LC-ESI-MS; Plant physiology and development; Plant root exudates; RP-LC
• ISSN: 1615-9306; 1615-9314
• DOI: 10.1002/jssc.200700234

Reversed-phase liquid chromatography with UV detection is of limited applicability in the separation and identification of carboxylic acids because of the column's poor separation efficiency and the non-selective nature of the UV detector. To address this issue, RP-LC with electrospray ionization mass spectrometry has been explored for the confirmation and determination of carboxylic acids in plant root exudates, with ESI-MS providing structural information, high selectivity, and high sensitivity. The separation of 10 carboxylic acids (pyruvic, lactic, malonic, maleic, fumaric, succinic, malic, tartaric, trans-aconitic, and citric acid) was performed on a C₁₈ column using an eluent containing 0.1% (v/v) acetic acid within 10 min, where the acidic eluent not only suppressed the ionization of the carboxylic acids to be retained on the column, but was also compatible with ESI-MS detection. In addition, an additional standard was used to overcome the matrix effect. The results showed that peak areas correlated linearly with the concentration of carboxylic acids over the range 0.05-10 mg/L. The detection limits of target acids (signal-to-noise S/N ratio of 3) ranged from 20 to 30 μg/L. Finally, the proposed method was used for the confirmation and determination of low-molecular-weight carboxylic acids in plant root exudates, and provided a simple analytical procedure, including sample processing, fast separation, and high specificity and sensitivity.