Melamine-formaldehyde aerogel coating for in-tube solid-phase microextraction.

A melamine-formaldehyde (MF) aerogel coating was prepared on basalt fibers (BFs) for in-tube solid-phase microextraction (SPME). MF aerogel-coated BFs were placed in a polyetheretherketone tube to obtain the extraction tube. To build an in-tube SPME-high performance liquid chromatography (HPLC) online system, the extraction tube was connected with HPLC equipment by replacing the sample loop of a six-port valve. The extraction tube was evaluated using eight polycyclic aromatic hydrocarbons (PAHs) as model analytes. After the optimization of important factors, an online analysis method was established. Wide linear ranges (0.03-25 μg L-1, 0.06-30 μg L-1) and low detection limits (0.01, 0.02, and 0.05 μg L-1) were observed. High sensitivity resulted from large enrichment factors ranging from 2070 to 3246. To validate the analysis method, two real water samples were detected. Most of the analytes were not detected in tap water and rainwater, and relative recoveries spiked at 2 and 5 μg L-1 were in the range of 80%-117%. The extraction repeatability on one tube and the preparation repeatability among three tubes were also tested, and their RSDs (n = 3) were in the range of 0.77%-2.04% and 0.88%-9.17%, respectively. As a result of the high surface area of the MF aerogel and π-π interactions with PAHs, the MF aerogel coating exhibits a superior extraction performance than other SPME materials, including wider linear ranges, lower LODs and higher enrichment factors.