| There is a high demand of infants for nutrients such as vitamins,proteins and trace elements.L-Carnitine and choline are the necessary water-soluble nutrients of infants,but the newborns can not provide adequate nutrition by themselves.Breast milk can do it,but there are many families can not provide enough breast milk for infants,so it is necessary that L-Carnitine and choline are added to infant formula food.Now we usually determination L-Carnitine and choline by enzyme-chromogenic and reddish salt colorimetric method respectively,however,this shortcoming is that the two methods not only can not accurate confirmation,and the detection limit is higher in the quantitative detection process,but the preparation process is complex and long of the samples,so it is not suitable for fast batch determination.At the above background,this paper research on detection method simultaneously of these water-soluble nutrients by isotope internal standard/liquid Chromatography/Tanderm Mass Spectrometry.The main experimental results are as follow:The sample was dissolved with warm water then was spiked with isotope internal standards(IS),after hydrochloric acid,ultrasonic extraction,the diluentionwas precipitated the protein with aqueous solution of formic acid acetonitrile,filtering through 0.22 ?m filter membrane.Then separating by Agilent HILIC column(3.5 ?m,100 mm×2.1 mm),the column temperature is 35?,The flow rate is 0.3 mL/min,the injection volume is 2 ?L,using gradient elution conditions.The qualitative and quantitative analysis was carried out by the multiple reaction ion monitoring mode(MRM),and the internal standard of the isotopes was corrected.The correlation coefficients of L-Carnitine and it's isotopic internal standard could reach 0.999 in the linear ranges of 0.005~0.100 mg/L,the linear ranger of choline and it's isotopic internal standard was 0.025~0.500 mg/L with square of the correlation coefficient above 0.999(standards).The average recoveries rate of L-Carnitine were 87.7%~101.0%,the average recoveries rate of choline were 80.6%~105.0%.And the relative standard deviations(RSD)of L-Carnitine and choline were less than 3.48% and 8.58% respectively.The detection limit(LOD)of L-Carnitine and choline was 1.5 mg/kg and 6.0 mg/kg respectively,and the quantitative limit(LOQ)of L-Carnitine was 4.5 mg/kg and choline was 18.0mg/kg(samples).This paper research on the application of the method that detection the actual content of samples in infant formula food by LC-MS/MS,and carry out the experiment of test experiment of actual sample,the restrictive transport conditions experiment and simulated experiment of infant formula powder.According to the experimental results,in the detected samples,the actual detection value of L-Carnitine and choline were reached about 80% on the label.It is suggested that the best storage temperature is 25? during a long period of transportion,and it could be storage in 0? to 37? during a short period of transportion.The optimum brewing water temperature for infant formula powder is 40?,and it's best to drink immediately,if not,it needs to be stored under refrigerated condition and the storage time should not exceed 72 h. |
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