determination of trace vitamin d in milk samples by graphene-based magnetic solid-phase extraction method coupled with hplc

In this paper, a kind of simple and environmental friendly sample pretreatment method was developed for analysis of vitamin d in milk samples. without saponification or protein precipitation, vitamin d2 and vitamin d3 could be captured directly from milk samples by graphene-coated magnetic particle (fe3o4@graphene) and separated by magnetic field with only 0.5-ml desorption solvent. the vitamin d2 and vitamin d3 were then detected by high-performance liquid chromatography (hplc). the main effect parameters including extraction time, solution ionic strength, desorption solvent, and desorption time were investigated. under optimized conditions, this method showed low detection limits (0.03 ng/ml for vitamin d2 and 0.08 ng/ml for vitamin d3), wide linearity, and good precision (2.7–3.6 % for intraday, 2.3–4.5 % for inter-day). the matrix interference-produced milk could be effectively eliminated using this method, and satisfactory recoveries of the spiked samples were 75.5 to 89.3 %. the results indicated that the fe3o4@graphene can be favorably used for the extraction of the vitamin d in milk samples. the reused material displayed a long-term stability after undergoing extraction of 100 times.