Dynamic changes in water-soluble vitamin components in the leaf extracts of sea buckthorn (Hippophae rhamnoides L.) via solid-phase extraction-ultra performance liquid chromatography and two-dimensional correlation analysis†

The extraction of B-series water-soluble vitamins from sea buckthorn leaves was studied using solid-phase extraction-liquid chromatography. The adsorption rates of water-soluble vitamins on amine-modified GO prepared from different amine compounds were compared, and the reaction product of triethylamine and GO was selected as an adsorbent with a high adsorption rate. The optimized solid phase extraction conditions for water-soluble vitamins using amine-modified GO included the use of methanol as the conditioning solvent, a pH 5.0 sample solution, and 0.2% formic acid-methanol solution as the desorption solvent. The sample was concentrated with the established solid-phase extraction method and measured using ultra-performance liquid chromatography (UPLC). The detection limits were 0.0016, 0.0033, 0.0021, 0.0050 and 0.0048 μg mL⁻¹ for vitamins B₁, B₂, B₃, B₆ and B₁₂, respectively, with relative standard deviation (RSD) less than 4.5%. The 2D chromatograms of the extracts of sea buckthorn leaves with different hot water extraction times were analyzed using the generalized 2D correlation method and the perturbation correlation-moving window 2D correlation method. The SPE method using amine-modified GO enhanced the vitamin component peaks in the sample and removed interfering components. The 2D correlation analysis results allowed visualization of the relationship between changes in the group B water-soluble vitamin components in the extract of sea buckthorn leaves with heating time.