Electrochemical detection of TNT with in-line pre-concentration using imprinted diethylbenzene-bridged periodic mesoporous organosilicas

We examined the adsorption and release of TNT using diethylbenzene-bridged (DEB) periodic mesoporous organosilica sorbents under varying conditions. The sorbents were applied for in-line target pre-concentration in conjunction with an electrochemical flow cell containing a glassy carbon electrode. Square wave voltammetry was employed for TNT detection. TNT sample volumes between 2 and 480 mL at concentrations ranging from 0.5 to 500 ppb were passed through the DEB sorbents (imprinted or not imprinted for TNT) at pH 6 (sodium acetate) or at pH 7.4 (PBS). Release of target was accomplished using solvent mixtures of methanol/water with sodium acetate as electrolyte or acetonitrile/water with PBS components as electrolyte. Under these conditions, the TNT was released in <200 μL of the solvent mixture, and pre-concentration factors of >3000 can be achieved when using large volumes of trace TNT samples. When sample volumes of 2 mL were utilized, the sensing system gave a linear response between 20 and 500 ppb with an estimated limit of detection of 13 ppb. When pre-concentrating 480 mL of sample in either buffered solution or seawater, detection of 0.5 ppb TNT was achieved with a signal to noise ratio of 20.