A new simple potentiometric sensor is developed and presented for sensitive and selective monitoring of dimethylamine (DMA). The sensor incorporates a molecularly imprinted polymer, with a pre-defined specific cavity suitable to accommodate DMA. The molecularly imprinted polymer (MIP) particles were dispersed in an aplasticized poly(vinyl chloride) matrix. The MIP is synthesized by using a template molecule (DMA), a functional monomer (acrylamide, AM), cross-linker (ethylene glycol dimethacrylate, EGDMA) and initiating reagent (benzoylperoxide, BPO). Using Trizma buffer solution (5 mmol L-1, pH 7.1), the sensor exhibits a rapid, stable and linear response for 1.0 × 10-5 to 1.0 × 10-2 mol L-1 DMA+ with a calibration slope of 51.3 ± 0.3 mV decade-1, and a detection limit of 4.6 × 10-6 mol L-1 (0.37 µg mL-1). The electrode exhibited a short response time (10 s) and stable potential readings (± 0.5 mV) for more than 2 months. Potentiometric selectivity measurements of the sensor reveal negligible interferences from most common aliphatic and aromatic amines. High concentration levels (100-fold excess) of many inorganic cations do not interfere. The sensor is successfully used for quantification of low levels of DMA down to 0.5 µg mL-1. Verification of the presented method was carried out after measuring the detection limit, working linearity range, ruggedness of the method, accuracy, precision, repeatability and reproducibility. Under flow-through conditions, the proposed sensor in its tubular form is prepared and introduced in a two-channel flow injection setup for hydrodynamic determination of DMA. The sampling rate is 50-55 samples h-1. The sensor is used to determine DMA in different soil samples with an accuracy range of 97.0-102.8%.
Keywords: flow injection analysis; method validation; molecularly imprinted polymers; potentiometric dimethylamine sensor; soil samples.