Melamine-formaldehyde aerogel functionalized with polydopamine as in-tube solid-phase microextraction coating for the determination of phthalate esters

To improve the extraction performance and stability of the melamine-formaldehyde (MF) aerogel, a melamine-formaldehyde aerogel functionalized with polydopamine (PDA/MF) has been prepared on the carbon fibers (CFs), and it was used as a solid-phase microextraction (SPME) material via packing into a polyetheretherketone (PEEK). The morphological structure of this SPME material was characterized by scanning electron microscope, and its performance was evaluated via coupled it with a high performance liquid chromatography (HPLC). The material exhibited good extraction performance for seven phthalate esters (PAEs). Compared with CFs and MF aerogel coated-CFs, PDA/MF aerogel coated-CFs have the best extraction efficiency for PAEs. Several influence factors were investigated in detail, including extraction volume, sampling flow rate, methanol content in sample and desorption time. Under the optimal conditions, an online in-tube SPME-HPLC analytical method was established with low limits of detection (LODs) (0.02-0.05 mu g L-1) and limits of quantification (LOQs) (0.07-0.16 mu g L-1), wide linear ranges (0.07-30 mu g L-1) and superior correlation coefficients (0.9954-0.9986). The relative standard deviations (RSDs, n = 3) of the method were in the ranges of 1.0-4.9% (infra-day) and 1.6-7.3% (inter-day), respectively. RSDs of preparation repeatability among three tubes ranged from 6.6% to 12.1%. The analysis method was applied to the detection of seven PAEs from three real samples. The proposed extraction material had good durability and chemical stability, and it also exhibited a superior extraction performance than other SPME materials, including lower LODs, higher enrichment factors and shorter extraction time.