Determination of fatty acids compositions and contents in Chinese mitten crabs by gas chromatography

Determination of fatty acid compositions and contents in Chinese mitten crabs is of great significance to evaluate its nutritional value and quality. However, in the face of a wide range of fatty acid extraction and methyl esterification reagents, the measurement results are uneven, and it is difficult to accurately quantify the rich fatty acids in Chinese mitten crabs. In this paper, four kinds of oil extraction reagents and two kinds of methylating reagents, were investigated. Chloroform-methanol (1∶1, v/v) was used as the extraction solvent, and methanol containing 2% sulfuric acid was used as the derivatization reagent. A method for the determination of fatty acids in the muscle of Chinese mitten crabs by gas chromatography was established. The experiment was carried out under the condition of programmed temperature rise, 37 kinds of fatty acids were separated on a DM-2560 capillary column (100 m×0.25 mm×0.20 μm), detected by hydrogen flame ionization detector (FID) and quantified by external standard method. The linear relationships of the 37 fatty acids were good in the range of 0.5-100.0 μg/mL. The correlation coefficients (R2) were 0.9981-0.9999. The limits of detection (LODs) and limits of quantification (LOQs) were 0.01-0.02 mg/100 g and 0.04-0.06 mg/100 g, respectively. The methodology was validated by palmitic acid and stearic acid. The recoveries were 76.0%-97.5%, and the relative standard deviations (RSD, n=5) were 3.31%-7.90% at the spiked levels of 1, 2 and 10 mg/100 g. The method was applied to the determination of fatty acid compositions and contents in the muscle of Chinese mitten crabs. A total of 31 kinds of fatty acids were detected. The length of carbon chain ranged from 12 to 24, and the total content of fatty acids reached 281.03 mg/100 g. Oleic acid, docosahexaenoic acid and eicosapentaenoic acid were the main fatty acids in the muscle of Chinese mitten crabs. Thus, this method provided accurate and reliable theoretical data for the determination of fatty acids in Chinese mitten crabs. This method has the advantages of simple operation, small amount of reagent and sample, reliable qualitative, accurate quantitative, detection of more fatty acid types. It is suitable for the rapid detection of fatty acid compositions and contents in muscle tissue of Chinese mitten crabs.