Silver ion functionalized covalent organic polymer for selective online solid phase microextraction of unsaturated fatty acid methyl esters

Abstract

In this work, silver ion functionalized covalent organic polymer (COPTAPB-BPDA@SA@Ag+) was fabricated via the introduction of silver ion to COP, and utilized as selective sorbent for online SPME of unsaturated fatty acid methyl esters (UFAMEs). The synthesis of COPTAPB-BPDA@SA@Ag+ was confirmed by using the SEM, EDS, FT-IR, XRD and XPS characterization techniques. Due to the charge-transfer interaction between silver ion and C = C double bonds, COPTAPB-BPDA@SA@Ag+ displayed satisfactory extraction ability towards UFAMEs. Several SPME factors, such as ACN content in the sampling solution and eluent, sampling and elution flow rate, were investigated with respect to the extraction efficiency of UFAMEs. Under the optimized conditions, an online Ag+-SPME-Ag+-HPLC method for analysis of target trans-UFAMEs was proposed. A good linearity was established in the range of 0.04 ∼ 2 mg/kg for two target trans-UFAMEs in milk tea samples. The limits of detection (LODs) and limits of quantitation (LOQs) were not more than 8.8 μg/kg and 19 μg/kg respectively, while the intra-day RSDs (n = 3) and the inter-day RSDs (n = 3) were less than 2.1% and 2.9% respectively. The recoveries for the proposed method was ranged from 82.3% to 93.5% with RSDs (n = 4) less than 5.9%. The above results demonstrated the selective extraction of COPTAPB-BPDA@SA@Ag+ towards UFAMEs from complex real samples, as well as the satisfactory detection sensitivity for trans-fatty acids of the proposed method. This study provided a facile approach for the preparation of metal ion functionalized COP sorbent and showed its wide potential for sample preparation.