Department of Chemistry and Center of Excellence for Innovation in Chemistry and Flow Innovation-Research for Science and Technology Laboratories (FIRST Labs), Faculty of Science, Mahidol University, Rama VI Rd., Bangkok 10400, Thailand.
National Doping Control Centre, Mahidol University, Rama VI Rd., Bangkok 10400, Thailand.
Talanta. 2017 Apr 1;165:612-618. doi: 10.1016/j.talanta.2017.01.010. Epub 2017 Jan 5.
Short-chain fatty acids, such as acetic, propionic, butyric, iso-valeric and valeric acids, play an important role in methanogenesis activity for biogas production processes. Thus, simple and rapid procedures for monitoring the levels of short-chain fatty acids are requisite for sustaining biogas production. This work presents the development of a sequential injection-liquid microextraction (SI-LME) procedure with GC-FID analysis for determination of short-chain fatty acids. GC-FID was employed for detection of the short-chain fatty acids. Calibration curves were linear with good coefficients of determination (r>0.999), using methacrylic acid as the internal standard. Limits of quantification (LOQ) were in the range of 0.03-0.19mM. The SI-LME procedure employed tert-butyl methyl ether (TBME) as the extracting solvent. Various SI-LME conditions were investigated and optimized to obtain the highest recovery of extraction. With these optimized conditions, an extraction recovery of the five key short-chain fatty acids of 67-90% was obtained, with less than 2% RSD (n=3). The final SI-LME procedure employed two fluidic zones of TBME with a single aqueous fluidic zone of sample sandwiched between the TBME zones, with 5 cycles of flow reversal at a flow rate of 5µL/s for the extraction process. Intra- and inter-day precision values were 0.5-4.0% RSD and 3.3-4.8% RSD, respectively. Accuracy based on percentage of sample recovery were in the range of 69-96, 102-107, and 82-101% (n=4) for acetic, propionic and butyric acids, respectively. The proposed method was applied for the measurement of short-chain fatty acids in palm oil mill effluents used in biogas production in a factory performing palm oil extraction process. The SI-LME method provides improved extraction performance with high precision, and is both simple and rapid with its economical extraction technique. The SI-LME procedure with GC-FID has strong potential for use as a quality control process for monitoring short-chain fatty acid levels in biogas production.
短链脂肪酸，如乙酸、丙酸、丁酸、异戊酸和戊酸，在沼气生产过程的产甲烷活性中起着重要作用。因此，监测短链脂肪酸水平的简单快速程序对于维持沼气生产是必要的。本工作提出了一种顺序注射-液相微萃取（SI-LME）与 GC-FID 分析相结合的方法，用于测定短链脂肪酸。GC-FID 用于检测短链脂肪酸。使用甲基丙烯酸作为内标，校准曲线呈良好的线性关系（r>0.999）。定量限（LOQ）在 0.03-0.19mM 范围内。SI-LME 程序采用叔丁基甲基醚（TBME）作为提取溶剂。考察并优化了各种 SI-LME 条件，以获得最高的萃取回收率。在这些优化条件下，5 种关键短链脂肪酸的萃取回收率为 67-90%，相对标准偏差（RSD）小于 2%（n=3）。最终的 SI-LME 程序采用两个 TBME 流体区，一个含有样品的单一水性流体区夹在 TBME 区之间，在 5µL/s 的流速下进行 5 个流动反转循环进行萃取过程。日内和日间精密度值分别为 0.5-4.0%RSD 和 3.3-4.8%RSD，分别。基于样品回收率的准确度范围分别为 69-96%、102-107%和 82-101%（n=4），分别用于乙酸、丙酸和丁酸。该方法用于测量工厂中用于沼气生产的棕榈油厂废水中的短链脂肪酸。SI-LME 方法具有高精密、简单快速、经济高效的萃取技术，可提高萃取性能。GC-FID 的 SI-LME 程序具有作为沼气生产中监测短链脂肪酸水平的质量控制过程的强大潜力。
