Property And Application Of Poly (N-isopropylacrylamide)-grafted Silica In High-performance Liquid Chromatography

In this study,poly-(N-isopropyl-acrylamide) bonded stationary phase (SI-PNIPAM) was prepared by reacting silica gel with 3-mercaptopropyltrimethoxysilane.Characterization of the prepared packing was carried out with Fourier transform infrared (FT-IR) spectroscopy. The application of SI-PNIPAM was researched by testing with polycyclic aromatic hydrocarbons,basic compounds and xylene isomers using methanol-water as a binary mobile phase in the field of chromatography . The thermal-responsibility of SI-PNIPAM for separating polarity compounds,basic compounds and isomers was also discussed . Practical application of SI-PNIPAM for the determination of preservatives cosmetics and vitamin E was researched finally.The results showed that the stationary phase has excellent chromatographic properties which greatly advanced the retention time and kept the same order for separation of polycyclic aromatic hydrocarbons by comparing with the result on ODS-BP. It also can be seen that SI-PNIPAM has excellent thermal-responsibility as well as PNIPAM. Using methanol-water(30 : 70) as mobile phase ,when a small temperature changed in the vicinity of 32℃, a narrow range of temperature , phase transition behavior of SI-PNIPAM will come to happen by changing the hydrophilic conformation for the hydrophobic conformation which lead to diferent order for separation in 28℃~ 32℃.However,the phase transition behavior responsing to temperature changed slowly,only the polar compounds with distinct difference in polarity had obvious performance in phase transition behavior.Preservatives of p-hydroxybenzoic acid esters could achieve baseline separation as well as symmetrical peaks on SI-PNIPAM in the mobile phase of methanol-water (55 : 45).Preservatives were extracted from cosmetics by the step of ultrasonic extraction and centrifugation,then Alumina column purification. Extraction was discussed by comparing the two extraction agents of methanol and ethanol–water.The results showed that ethanol–water was the better extraction agent for preservatives of p-hydroxybenzoic acid esters.The results for the recovery,reproducibility.the linear range and CV were good.The method which consisted of the preservative extraction and chromatographic separation on SI-PNIPAM could be applied to determine the preservatives in cosmetic preparations.The actual determination of preservatives in cosmetic sales obtained a more satisfactory result by using this new method.Using SI-PNIPAM as stationary phase, a RP-HPLC method has been established for the quantitative determination of Vtiamin E in capsule by.Results showed that the method was convenient,rapid,accurate and reliable. SI-PNIPAM used as a nomal-phase column could be applied for analysis of natural vitamin E with good separation.