Vitamin determination in pet food: A fast and sensitive online solid-phase extraction and heart-cutting 2D liquid chromatography method

An automatic method that combines online solid-phase extraction (online SPE) and heart-cutting two-dimensional liquid chromatography (2D-LC) was developed to determine seven fat-soluble vitamins simultaneously and was validated in pet food. The saponified sample solution was injected directly into our combined online SPE and heart-cut 2D-LC system for enrichment, purification, separation, and quantification. Vitamin A and E isomers were analyzed using pentafluorophenyl (PFP) as the first column. Vitamins D 2 and D 3 were analyzed using C 18 as the second column. The results showed good linearity (R 2  > 0.9964) for the analytes and good reproducibility (RSD < 3 %, n = 3). The limits of quantification for vitamins A, D 2 , and D 3 , and α −, β-, γ-, and δ-E (calculated using S/N = 10:1) were 0.24, 0.09, 0.09, 2.4, 2.4, 2.4 and 2.4 μg/g, respectively. The spiked recoveries were from 80.6 to 104.0 %. The proposed method considerably simplifies the analytical workflow of standard methods for the analysis of fat-soluble vitamins and improves efficiency.