ABSTRACT
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%.
ABSTRACT
Novel biomimetic potentiometric ion-selective electrodes (ISEs) were fabricated and designed for the assessment of aminoacridine (ACR) based on newly synthesized imprinted polymer (MIP) membranes. Thermal polymerization of methacrylic acid (MAA) or acrylamide (AM) as function monomer, aminoacridine as a template and ethylene glycol dimethacrylate (EGDMA) as across-linker, were utilizedto give the molecular recognition part. The membranes of sensors I andII consist of MIP based MAA and AM, respectively, dispersed in a poly(vinyl chloride) membrane plasticized with dioctyl phthalate (DOP) in the ratio of 3.0 wt%, 32.2 wt% and 64.8 wt%, respectively. Sensors III and IV were similarly prepared with added 1.0 wt% tetraphenyl borate (TPB-) as an anionic discriminator. Sensors I and II exhibited near-Nernstian potential response to ACR+ with slopes of 51.2 ± 1.3 and 50.5 ± 1.4 mV/decade in a 0.01 M phosphate buffer of pH 6.0. The linear response coversthe concentration range of 5.2 × 10-6 to 1.0 × 10-3 M with a detection limit of 0.05 and 0.17 µg/mL for sensors I and II, respectively. The performance characteristics of these sensors were evaluated under static and hydrodynamic mode of operations. They were used for quality control assessment of aminoacridine in some pharmaceutical preparations and biological samples.
ABSTRACT
Molecularly imprinted polymer (MIP) receptors have been synthesized, characterized, and applied as new selective receptors in solid-contact ion selective electrodes (ISEs) towards non-dissociated 3,5-dihydroxytoluene (orcinol). Two monomers, namely methacrylic acid (MAA) and acrylamide (AA), were used in the preparation of MIP receptors. Graphene (Gr) was used as the solid contact material between the sensing membrane and the electrical contact substrate. Based on non-equilibrium sensing mechanism, the proposed sensors reveal observably enhanced detection sensitivity towards orcinol with detection limits 1.7 × 10-5 and 3.3 × 10-6 M for sensors based on MIP/MAA and MIP/AA, respectively. The selectivity coefficients measured by the modified separate solution method (MSSM) for the proposed sensors showed good selectivity towards orcinol over most common other phenols and inorganic anions. All measurements were made in the presence of 30 mM phosphate buffer solution (PBS) with a pH of 7.0. Potential stability for the proposed sensors was tested by constant-current chronopotentiometry. No water films were formed between the sensing membrane and the electron conductor substrate. The applicability of MIP/MAA incorporated ISE has been checked by recovery test of orcinol in the presence of soil matrix and by standard addition method.
ABSTRACT
Two novel all-solid-state potentiometric sensors for the determination of azide ion are prepared and described here for the first time. The sensors are based on the use of iron II-phthalocyanine (Fe-PC) neutral carrier complex and nitron-azide ion-pair complex (Nit-N3-) as active recognition selective receptors, tetradodecylammonium tetrakis(4-chlorophenyl) borate (ETH 500) as lipophilic cationic additives and poly(octylthiophene) (POT) as the solid contact material on carbon screen-printed devices made from a ceramic substrate. The solid-contact material (POT) is placed on a carbon substrate (2 mm diameter) by drop-casting, followed, after drying, by coating with a plasticized PVC membrane containing the recognition sensing complexes. Over the pH range 6-9, the sensors display fast (< 10 s), linear potentiometric response for 1.0 × 10-2â»1.0 × 10-7 M azide with low detection limit of 1.0 × 10-7 and 7.7 × 10-8 M (i.e., 6.2â»4.8 ng/ml) for Fe-PC/POT/and Nit-N3-/POT based sensors, respectively. The high potential stability and sensitivity of the proposed sensors are confirmed by electrochemical impedance spectroscopy (EIS) and constant-current chronopotentiometry measurement techniques. Strong membrane adhesion and absence of delamination of the membrane, due to possible formation of a water film between the recognition membranes and the electron conductor are also verified. The proposed sensors are successfully applied for azide quantification in synthetic primer mixture samples. Advantages offered by these sensors are the robustness, ease of fabrication, simple operation, stable potential response, high selectivity, good sensitivity and low cost.
