Abstract:
Direct coupling of porous polymer thin film microextraction (TFME) devices to either benchtop or hand-held mass spectrometers presents a unique opportunity to streamline contaminant screening protocols for water and food. With a wide variety of monomers available, porous organic covalent networks can be tailored for selectivity, porosity, surface area, and sample compatibility; they can also be prepared as a stand-alone membrane or as a coating on almost any substrate. In a process that has come to be known as molecular imprinting, addition of a template molecule provides a scaffold for functional monomers to yield cavities with favourable orientation of functional groups to increased binding affinity for low analyte concentrations. Through careful control of the porogenic solvent loading, imprinting can be enhanced and polymer porosity tuned to balance the surface area needed for high extraction efficiency (microporous) against desirable mass-transfer dynamics (macroporous), the latter being of particular concern during direct MS interrogation where quick desorption is crucial. In this talk the details of two formats of porous imprinted polymers will be presented. The first is a coated blade format for extraction of bioactive molecules from a range of aqueous matrices. The coated blade performance as an extraction device for natural and synthetic samples was confirmed with Waters Acquity ultra high performance liquid chromatography system coupled to a Waters Xevo TQ-S MS/MS (UHPLC-MS/MS). The second format is a coated mesh device designed with higher surface area than the blades. This device was first validated using UHPLC-MS, then tested with the thermal desorption accessory of a MX908 hand-held mass spectrometer. Data on the polymer and method optimizations will be presented along with preliminary data from the MX908. The challenges associated with ultra-trace analysis using small hand-held MS and future prospects will be discussed.