LC-MS Determination Of Organic Acids In Fruits And Vegetables

The amount and variety of organic acid in fruits and vegetables have a significant influence on the flavor that people taste. Organic acid functions to promote the absorption of calcium and iron, improve immunity, promote the body’s metabolism, improve endocrine disorders and so on. Hereby in this study, by adopting the LC-MS method, thus to develop a new method in order to solve the problems including application scope limitation of the traditional testing method, severe impact caused by impurities, low sensitivity, complicated pre-treatment method, and narrow analyzing and testing scope.In this research, a method called ultra high performance liquid chromatography- mass spectrometria(LC-MS) is developed to test six kinds of organic acids in fruits and vegetables, including tartaric acid, malic acid, citric acid, succinic acid, fumaric acid and maleic acid. In this process, ACQUITY UPLC® HSS T3 chromatographic column separation is adopted, 0.1% formic acid/acetonitrile- 0.1% formic acid/water system as the mobile phase in gradient elution, flow rate of 0.25 mL/min, at the same time through the ESI- scan multiple reaction monitoring mode, in order to determine the mass-to-charge ratio of ion pair, optimize the taper hole voltage, and collision mass spectrometry conditions such as voltage. The linear rangeobtained by drawing standard curve of organic acid in fumaric acid and maleic acid is 0~1000 ng/mL, and in malic acid, citric acid, tartaric acid and succinic acid is 0~2000 ng/mL.The correlation coefficient between R2 is 0.9989~0.9998.The method of the minimum detection limits are 0.02 ug/mL and 0.05 ug/mL, while the minimum quantitative limits are 0.1 ug/mL and 0.25 ug/mL respectively.This research acquires the recycling rates by extracting organic acid of fruits and vegetables from 40% ethanol- water solution twice, SAX solid-phase extraction column for purification, using the capacity, the mobile phase for a 0.22 um filtered water film on, and using standard experimental samples. The range of the average recycling rate of cabbage samples is 81.1% ~102.2%, relative standard deviation between the scope of the RSD is 2.0%~7.3%. The range of the average recycling rate of raspberry is 78.7% ~ 104.0%, relative standard deviation between the scope of the RSD is 2.5%~12.4%.Then mark samples will be added in the fridge and retested after 72 hours and 144 hours respectively, and it turns out to be that no obvious change occur peak area, retention time, and response value. Since the relative standard deviation is between 1.29% ~ 9.99%, it indicates that the method is stable and accurate with high recycling rate.