Desorption electrospray ionization-mass spectrometry for the detection of analytes extracted by thin-film molecularly imprinted polymers

Desorption electrospray ionization-mass spectrometry (DESI-MS) is a powerful technique for the analysis of solid and liquid surfaces that has found numerous applications in the few years since its invention. For the first time, it is applied to the detection of analytes extracted by molecularly imprinted polymers (MIPs) in a thin-film format. MIPs formed with 2,4-dichlorophenoxyacetic acid (2,4-D) as the template were used for the extraction of this analyte from aqueous solutions spiked at concentrations of 0.0050-2.0 mg L-1 (similar to 2 x 10(-8) to similar to 1 x 10(-5) M). The response was linear up to 0.50 mg L-1, and then levelled off due to saturation of the active sites of the MIP. In MS/MS mode, the signal at 0.0050 mg L-1 was still an order of magnitude higher than the signal of a blank. The MIP DESI-MS approach was also used for the analysis of tap water and river water spiked with 2,4-D and four analogues, which indicated that these analogues were also extracted to various extents. For practical applications of the MIP, a detection technique is required that can distinguish between these structurally similar compounds, and DESI-MS fulfills this purpose.