Analysis of Ascorbic Acid and Isoascorbic Acid in Orange and Guava Fruit Juices Distributed in Thailand by LC-IT-MS/MS

作者：Boonpangrak Somchai; Lalitmanat Sasiwimon; Suwanwong Yaneenart; Prachayasittikul Supaluk; Prachayasittikul Virapong^*

来源：Food Analytical Methods, 2016, 9(6): 1616-1626.

DOI：10.1007/s12161-015-0337-x

• Ascorbic acid
• Isoascorbic acid
• LC-MS/MS
• Ion trap
• ESI
• Fruit juices

This work describes the determination of ascorbic acid (AA) and isoascorbic acid (IAA) in fruit juices by liquid chromatography coupled with ion trap tandem mass spectrometry (LC-IT-MS/MS), with a reversed phase column (C-18) and simple isocratic conditions of 0.1 % formic acid. The negative ion mode of electrospray ionization (ESI) and the MS/MS transition of m/z 175 were used for the quantitation of AA- and IAA-generated product ions with m/z 115. The method was validated in terms of linearity, limit of detection (LOD), limit of quantitation (LOQ), precision, and accuracy. Good linearity was achieved with 0.6 and 1.8 mu g/mL for the LOD and LOQ, respectively. The intraday and intermediate precisions were approximately 4 and 7 %, respectively. Recovery percentages ranged from 88 to 108 %. All validation parameters were found to be within the acceptable range for both AA and IAA. Hence, the proposed method is suitable for simultaneously determining AA and IAA. Fourteen fruit juice samples were analyzed including fruit juices from supermarkets, local markets, and laboratory preparations. Ten fruit juice samples (100 %) from different brands in the supermarkets were investigated for AA and IAA content. AA could be detected in all the samples, ranging from 5.2 +/- 2 to 44.4 +/- 1.3 mu g/mL, and the values of vitamin C in 4 guava samples were less than the values specified by the manufacturer. IAA was observed in 4 of 10 samples ranging from 3.4 +/- 0.9 to 78.3 +/- 3.9 mu g/mL, and the highest value of IAA was approximately two fold higher than the highest value of AA. For freshly prepared fruit juices, AA was detected in both local market- and laboratory-prepared juices. The value ranged from 13.2 +/- 0.9 to 105.1 +/- 1.3 mu g/mL. In addition, the AA stability after opening the package was evaluated. The results showed that after 4 days of storage in the refrigerator, approximately 30 and 15 % losses of AA were observed for the orange and guava juices, respectively. Fresh fruit juices were thus demonstrated to be good sources of AA, with the highest value observed for guava juice prepared in the laboratory.

• 出版日期2016-6