Determination of steviol glycosides in commercial Soju using UPLC-TQ-MS/MS with product ion confirmation scan (PICS) mode

Steviol glycosides (SGs), derived from Stevia rebaudiana, are of increasing interest as potent low-calorie sweetener. However, there is still unclear regulation for estimating the maximum limit of their usage in food products and daily intakes, due to limited information on quantitative analytical protocols for SGs. In the present study, optimized settings for ultraperformance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) with product ion confirmation scan (PICS) mode for separation and quantitation of all 13 SGs were discussed. As a result, UPLC-TQ-MS/MS method with PICS mode presented excellent linearity (R-2 > 0.999), limits of detection (0.03-0.04 mg/L), and limits of quantitation (0.09-0.12 mg/L), along with high accuracy (recovery 97.4-105.6 %) and precision (RSD 0.35-3.24 %), within 35 min. The validated method was then applied to analyze 10 commercial Korean distilled liquors, Soju. All Soju samples were diluted with a five-fold volume of the acetonitrile (ACN) and deionized water mixture (3:7, v/v) for further analysis. Mostly, rebaudioside A exhibited the highest content with large variation, while both rebaudioside E and O were the lowest content with the smallest variation. The separation and quantitation methods for SGs can be applied for liquid food quality control and the obtained results can be useful to the guideline for daily amounts of drinking Soju for the public.