School of Science and Technology, Chemistry Division, University of Camerino, Via Madonna delle Carceri 9/B, 62032 Camerino, Italy.
Department of Agricultural, Food and Environmental Science, Polytechnic University of Marche, 60131 Ancona, Italy.
Molecules. 2022 Nov 24;27(23):8195. doi: 10.3390/molecules27238195.
A new analytical method for the determination of six volatile short and medium-chain fatty acids (acetic, propionic, isobutyric, isovaleric, hexanoic, and octanoic acids) through liquid-liquid extraction with diethyl ether, followed by GC-FID analysis, was developed and validated. The extraction conditions were optimized by evaluating the effect of the number of extractions (1 to 3) and the effect of the addition of salts (NaHPO, (NH)SO, NaCl, (NH)SO/NaHPO) to increase the concentration of the analytes in the ethyl ether phase. Results showed that a single extraction allows obtaining the highest sensitivity (due to the impossibility of evaporating the solvent to avoid losses of the analytes). The use of salting out agents, in particular, NaHPO, showed an important increase in the extraction extent, on average, 1.5 times higher as compared to the extraction performed without salt. The proposed method is rapid, requiring a total of 30 min for preparation and analysis, and it makes use of small amounts of sample (500 µL) and solvent (400 µL). The method was then applied to quantify the analytes in 5 white wines and 5 red wines, allowing to highlight some clear differences between red and white wines, with the red ones having a significantly higher amount of acetic acid (715.7 ± 142.3 mg/L in red wines and 351.5 ± 21.2 mg/L in white wines) and the white wines having a significantly higher amount of hexanoic and octanoic acid (6.1 ± 3.0 mg/L and 2.6 ± 0.8 mg/L, respectively, are the mean concentrations in white wines, and 4.7 ± 0.8 and 2.4 ± 0.4 mg/L, respectively, are the mean concentrations in red wines).
一种新的分析方法，通过乙醚液液萃取，随后进行 GC-FID 分析，用于测定六种挥发性短链和中链脂肪酸（乙酸、丙酸、异丁酸、异戊酸、己酸和辛酸）。通过评估萃取次数（1-3 次）和添加盐（NaHPO、(NH)SO、NaCl、(NH)SO/NaHPO）的效果来优化萃取条件，以增加分析物在乙醚相中的浓度。结果表明，单次萃取可获得最高的灵敏度（由于不可能蒸发溶剂以避免分析物的损失）。使用盐析剂，特别是 NaHPO，可显著提高萃取程度，与不使用盐的萃取相比，平均提高了 1.5 倍。该方法快速，制备和分析总共需要 30 分钟，且仅需 500µL 样品和 400µL 溶剂。该方法随后用于定量分析 5 种白葡萄酒和 5 种红葡萄酒中的分析物，能够突出红葡萄酒和白葡萄酒之间的一些明显差异，红葡萄酒中乙酸的含量明显较高（715.7±142.3mg/L，而白葡萄酒中乙酸的含量为 351.5±21.2mg/L），而白葡萄酒中己酸和辛酸的含量明显较高（6.1±3.0mg/L 和 2.6±0.8mg/L，分别为白葡萄酒的平均浓度，4.7±0.8mg/L 和 2.4±0.4mg/L，分别为红葡萄酒的平均浓度）。
