Development of polyacrylic acid-functionalized porous zinc sulfide nanospheres for a non-aqueous solid phase extraction procedure toward alkaloids

A polymer- based cation exchanger and silica-based sorbents are generally used for the conventional solid phase extraction (SPE) toward alkaloids, because they provide both ion exchange interactions and strong hydrophobic interactions between the stationary phase and samples. However, strong hydrophobic interactions could cause the retention of some non-alkaloid compounds, to reduce the selectivity for alkaloids. In this paper, a non-aqueous solid phase extraction (SPE) procedure was developed and optimized utilizing novel polyacrylic acid-functionalized porous zinc sulfide nanospheres (PAA-PZNs) as the sorbents for the enrichment of alkaloids. The SPE sorbents were fabricated by the amidation reaction of the poly-(acrylic acid) homopolymer with amino group modified PZNs, which afforded an abundance of carboxyl groups, to effectively eliminate non-alkaloid compounds and concentrate alkaloids from the extracts. They exhibited not only high extraction efficiency, high selectivity and high recoveries for alkaloids, but also good chemical and mechanical stability. Therefore, the PAA functionalized porous zinc sulfide nanospheres and subsequently prepared non-aqueous solid phase extraction (SPE) procedure may prove to be a strong tool for selective enrichment of alkaloids from extracts.