Analysis of thiophenes in seawater: Molecularly imprinted polymer thin-film extraction with desorption electrospray ionization mass spectrometry

Abstract A new method coupling molecularly imprinted polymer thin-films (MIP thin-films) with desorption electrospray ionization mass spectrometry (DESI-MS) has been developed for indirect analysis of thiophene compounds in water. MIP thin-films were prepared on non-porous glass slides using a simple drop-casting fabrication method. The resulting films were used for indirect quantitative analysis of thiophene compounds in water by sorbing thiophene oxidation products (sulfones) to MIP films, then interrogating the MIP surface by DESI-MS. Oxidation of thiophenes to sulfones in water was achieved by reaction with a mixture of H 2 O 2 /formic acid at 65 °C for 2 h. DESI source parameters were optimized, and the optimal spray solvent composition was found to be MeOH:H 2 O (95:5 v/v) containing 0.5 mM NaCl. Among all sulfones formed, the protonated ion and sodium adduct signals were observed only for dibenzothiophene sulfone. The method was applied to dibenzothiophene in seawater, yielding a limit of detection at 3 ng L −1 and relative standard deviations (RSDs) below 8.0%. DESI-MS response was linear (R 2  = 0.9841) over the range studied 0.1–10 μg L −1 . With limited sample handling and ease of sample processing, many samples can be processed simultaneously making the method suitable for high throughput of screening environmental waters for dibenzothiophene and has the potential for detection its sulfone-metabolite.