Chen Zuliang, Jin Xiaoyin, Wang Qinqping, Lin Yuman, Gan Li, Tang Caixing
School of Chemistry and Materials Science, Fujian Normal University, Fuzhou, China.
J Sep Sci. 2007 Oct;30(15):2440-6. 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 C(18) 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 microg/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.
由于柱分离效率低以及紫外检测器的非选择性，带有紫外检测的反相液相色谱在羧酸的分离和鉴定方面适用性有限。为了解决这个问题，已探索采用带有电喷雾电离质谱的反相液相色谱来确认和测定植物根系分泌物中的羧酸，电喷雾电离质谱可提供结构信息、高选择性和高灵敏度。在C(18)柱上，使用含有0.1%（v/v）乙酸的洗脱液在10分钟内对10种羧酸（丙酮酸、乳酸、丙二酸、马来酸、富马酸、琥珀酸、苹果酸、酒石酸、反式乌头酸和柠檬酸）进行分离，其中酸性洗脱液不仅抑制了待保留在柱上的羧酸的电离，而且还与电喷雾电离质谱检测兼容。此外，使用了一种额外的标准物来克服基质效应。结果表明，在0.05 - 10 mg/L范围内，峰面积与羧酸浓度呈线性相关。目标酸的检测限（信噪比S/N为3）在20至30 μg/L之间。最后，所提出的方法用于确认和测定植物根系分泌物中的低分子量羧酸，并提供了一个简单的分析程序，包括样品处理、快速分离以及高特异性和高灵敏度。
