In situ modification of silica with poly(vinyl alcohol) for normal-phase liquid chromatographic separation of bioactive compounds in traditional Chinese medicines

Abstract

Porous silica beads were coated with poly(vinyl alcohol) by using an in situ coating process. This system has been developed for use as a stationary phase in normal phase high performance liquid chromatography. In the conditions, the coating efficiency was controlled by the initial concentration of poly(vinyl alcohol). The polymer coating has been characterized by scanning electron microscopy, the nitrogen adsorption/desorption method, and infrared spectra analysis. The performance of the developed stationary phase was evaluated by separation of 5 nucleosides (thymidine, thymidine, uridine, adenine, and 2′,3′-dideoxyadenosine), 2 anthraquinones (rhein and emodin) and 1 terpenoid (oleanolic acid) in 10 traditional Chinese medicines. Comparison studies showed that the poly(vinyl alcohol) coated silica stationary phase showed better separation performance than bare silica beads. The obtained limits of detection for these analytes varied from 0.02 to 0.64 mg L⁻¹. The linear ranges were from 1 to 1000 mg L⁻¹ with the correlation coefficient (r) from 0.9990 to 0.9999. The average recoveries were in the range of 95.60–103.12%. This preparation process did not require chemical synthesis processes and techniques. The developed column offered a simple and convenient approach to obtain normal phase liquid chromatographic columns with satisfactory separation efficiency.