Interdepartmental Centre for Industrial Research "Energy and Environment" and Department of Chemistry "Giacomo Ciamician", University of Bologna, Campus of Ravenna, via S.Alberto 163, I-48123 Ravenna, Italy.
Interdepartmental Centre for Industrial Research "Energy and Environment" and Department of Chemistry "Giacomo Ciamician", University of Bologna, Campus of Ravenna, via S.Alberto 163, I-48123 Ravenna, Italy.
Anal Chim Acta. 2018 Nov 30;1034:92-101. doi: 10.1016/j.aca.2018.06.082. Epub 2018 Jul 3.
Volatile fatty acids (VFAs) are among the most important parameters in process monitoring of anaerobic digestion plants for biogas production. The concentration of single VFA species is typically determined by direct injection of the acidified aqueous phase of digestate samples into GC-FID. Analysis of dimethyl carbonate extracts was investigated as an alternative method consisting of a simple and rapid in-vial procedure of acidification and solvent extraction of the sample, followed by centrifugation and GC-MS analysis. The principal figures of merit resulting from internal standard calibration were comparable to those proposed for the direct analysis of aqueous digestate, while the analysis of real samples did not provide statistically significant differences between the two methods according to parametric and non-parametric tests. Procedural aspects including sample amount and solid removal improved with dimethyl carbonate, while GC contamination was reduced. The method was applied to seventeen samples from fully operating anaerobic digesters fed with various feedstocks and enabled the individuation of high probability of system stress through the values of total VFA, propanoic acid, longer chained VFA concentrations and the ratio between acetic and propanoic acid concentrations. The use of dimethyl carbonate allowed the detection of alicyclic and aromatic acids that could represent new molecular markers in assessing the origin of feed and process conditions.
挥发性脂肪酸（VFAs）是沼气生产厌氧消化厂过程监测中最重要的参数之一。单一 VFA 物种的浓度通常通过直接将酸化的消化物样品的水相注入 GC-FID 来确定。研究了二甲基碳酸酯提取物的分析作为一种替代方法，该方法包括酸化和样品溶剂萃取的简单快速的瓶内程序，然后进行离心和 GC-MS 分析。内标校准得出的主要优点与直接分析水相消化物提出的优点相当，而根据参数和非参数检验，实际样品的分析并未显示两种方法之间存在统计学上的显著差异。包括样品量和固体去除在内的程序方面得到了改善，而 GC 污染则减少了。该方法应用于 17 个来自各种进料完全运行的厌氧消化器的样品，并通过总 VFA、丙酸、长链 VFA 浓度以及乙酸和丙酸浓度之间的比值的值，能够确定系统压力的高概率。二甲基碳酸酯的使用允许检测到脂环酸和芳香酸，它们可能是评估进料和工艺条件来源的新分子标记。
