Ultrasonic-microwave method in preparation of polypyrrole-coated magnetic particles for vitamin D extraction in milk

In this study, a nanocomposite of polypyrrole-coated magnetite nanoparticles (Fe3O4@PPy) was prepared by ultrasonic-microwave technique, and employed as magnetic solid-phase extraction (MSPE) sorbent for extraction of vitamin D from milk samples. The term of the synthesis by ultrasonic-microwave technique was dramatically shortened within 4 h compared to 20 h by conventional stirring-heating method. The resultant composites incorporating the pi-pi bonding (between PPy coating and the analytes) and magnetic separation can be applied for vitamin D analysis in complicated samples. Without saponification or protein precipitation, vitamin D-2 and vitamin D-3 could be captured directly from milk samples by Fe3O4@PPy, and separated by magnetic field with only 0.5 mL desorption solvent. The total preparation time was completed within 15 min. A method for the determination of vitamin D in milk samples by the Fe3O4@PPy extraction coupled with high performance liquid chromatography (HPLC) was developed. The LODs of vitamin D-2 and vitamin D-3, based on signal-to-noise ratio (S/N) of 3, were 0.02 ng/mL and 0.05 ng/mL respectively. The recoveries of vitamin D-2 and vitamin D-3 from milk samples were in the range of 71.9-90.3%, with relative standard deviations ranging between 3.6%-9.9%. The results indicated that the Fe3O4@PPy can be favorably used for the extraction of the vitamin Din milk samples. (C) 2016 Elsevier B.V. All rights reserved.