Abstract: Objective To improve the pretreatment method for determination of docosahexaenoic acid（DHA） in infant formula milk powder by gas chromatography. Methods The improved method adopts hydrolysis，extraction，saponification and methyl esterification of fats in 50 mL polypropylene centrifuge tubes，which avoids the use of traditional heating reflux devices and liquid-liquid extraction and separation funnels. Results The DHA standard solution showed a good linear relationship between 9.54 and 191 μg/mL concentration，and the correlation coefficient r was 0.999 8. The detection limit of the method was 0.001 g/100 g and the quantitative limit was 0.003 g/100 g. The samples were added to the DHA standards of low，medium and high concentration levels，and the recovery rate of the standard was 84.3%-108.0%，and the relative standard deviation（RSD） was <10% for six repeated measurements. The DHA in the quality control sample and examination sample of infant formula milk powder was determined，and the measurement results were within the range of their identified values. Conclusion The improved pretreatment method is simple and fast，and is suitable for the large-scale detection of DHA in infant formula milk powder.

Key words: Fatty acids, Methyl esterification, Docosahexaenoic acid, Milk powder