Determination of vitamin D3 in daily oily supplements by a two-dimensional supercritical fluid chromatography-liquid chromatography-mass spectrometry system

•A two-dimensional column switching system involving SFC and RPLC-MS is developed.•The system works at SFC-MS or SFC-LC-MS mode through switching two six-port valves.•Vitamin D in oily supplements can be determined simply and fast using this system.•SFC-LC-MS can get more accurate result with better precision even if using ES method. A two-dimensional system composed of supercritical fluid chromatography (SFC) and reverse phase liquid chromatography (RPLC) coupled a tandem mass spectrometry (MS) was developed for the quantitative analysis of vitamin D in daily oily supplements. Two six-port switching valves are configured, allowing four different valve positions. When the valve positions were fixed at Position A, this system worked at SFC-MS mode. When the valve positions switched between Position B and C, this system worked at a SFC-LC-MS switching mode. Vitamin D3 in two kinds of oily drops, Baby Ddrops and Vitamin AD drops, was determined at both SFC-MS and SFC-LC-MS switching modes by using the same system. The linearity, repeatability and recovery were investigated using the internal and external standard methods for the two modes. The results obtained from the internal standard method are better than those of the external standard method at either mode. The coefficient of determination (r2) for the internal standard method is more than 0.999, with a linear range of 20–1000 μg/L. Both Baby Ddrops and Vitamin AD drops were analyzed with good repeatability (0.999), repeatability (Baby Ddrops: 4.45%, Vitamin AD drops: 1.12%) and recovery (86.3%–107.1%). The results indicate that the two-dimensional SFC-MS/SFC-LC-MS system is useful for determination of vitamin D in oily drops. If it works at SFC-MS mode, the internal standard is required. When SFC-LC-MS switching mode is used, external standard method can also obtain the accurate results with good precision.