Abstract: With the development and utilization of hydrolyzed whey protein raw materials in infant food,it has caused huge difficulties in the detection of pantothenic acid in milk powder. This method was developed to solve the problem of the interference of hydrolyzed proteins on the detection. The milk powder sample was dissolved in warm water,adjusted pH value,and precipitated protein,and was separated by HSS T3 liquid chromatography column method,detected by single quadrupole mass spectrometry after spray ionization,isotope internal standard method for quantification. The results showed that the limit of quantification of the method was 0.0141 mg/100 g,the recoveries of the low,medium and high standard addition levels in the linear range were 92.0%~102.7%,and the relative standard deviations were 0.31%~2.23%. There was no significant difference in the determination results of pantothenic acid in goat milk powder and milk powder matrix samples by the national standard method. The method has simple operation process,short analysis period,high sensitivity and good repeatability,is suitable for the determination of pantothenic acid in special medical formula milk powder and infant formula milk powder,especially for milk powder samples with added hydrolyzed protein,has great prospect.

Key words: liquid chromatography-single quadrupole mass spectrometry（QDA）, pantothenic acid, hydrolyzed protein