Potentiometric Sensing of Neutral Species Based on a Uniform‐Sized Molecularly Imprinted Polymer as a Receptor

Abstract

Polymeric membrane ion-selective electrodes (ISEs) have been routinely used for determination of ionic species in clinical applications and for the determination of water quality owing to their attractive features including excellent selectivity, low cost, ease of use, and high reliability. [1][2][3] This well-established analytical technology has undergone a quiet revolution over the last few years. The detection limits of ISEs have been lowered from the micromolar to the subnanomolar range, and the discrimination of interfering ions has been improved by many orders of magnitude.[4] Currently, the application of ISEs has evolved to provide a promising measurement technique for environmental trace analysis and potentiometric biosensing. However, it has remained an open challenge for analytical chemists to develop potentiometric sensors for uncharged molecules, since the prerequisite for the general mechanism of potentiometric response is the occurrence of a charge on an analyte. Very few ISEs have been reported for which the membrane potentials are affected by neutral molecules. Electrodes formulated with plasticized poly(vinyl chloride) (PVC) membranes containing tetraphenylborate salts of barium complexes with given polyethoxylates [5a-c] or hydrogen-ion carriers [5d] show cationic responses to acyclic polyether-based nonionic surfactants, which are attributed to the partitioning of the surfactant/ metal cation complexes coextracted into the membranes. Anionic responses are induced by undissociated neutral phenols using PVC matrix liquid membranes containing lipophilic nitrogen-containing compounds [6a-b] or metal porphyrins [6c] as sensory elements. The net movement of protons from the membrane interface to the aqueous phase stimulated by uncharged phenols is responsible for the anionic response. Although these approaches have made great contributions toward the potentiometric detection of neutral species, the sensors developed show rather poor selectivities because the potential response is governed mainly by the lipophilicity of the neutral molecules, rather than specific molecular recognition. So far, a potentiometric sensor with a synthetic carrier that selectively binds neutral species is still apparently unknown. [2b] As highly suitable receptors, molecularly imprinted polymers (MIPs) have emerged as attractive, simple, and seemingly general materials for the selective binding of a wide range of analytes with affinities and selectivities similar to those of antibodies, enzyme, and hormone receptors. [7][8][9][10] Compared to their biological counterparts, MIPs are more stable, less costly, and easier to produce. Such materials are synthesized in the presence of functional monomers, template molecules, and a cross-linking agent by covalent, [11] noncovalent, [12] and sacrificial spacer methods. [13] Binding sites with molecular recognition properties are formed after template molecules have been removed from the polymerized material, leaving behind cavities for the subsequent rebinding process tha...

Potentiometric Sensor Based on Molecularly Imprinted Polymers for Rapid Determination of Clenbuterol in Pig Urine

“…As shown in Fig.1a, the MIP beads are spherical with a diameter distribution of 0.5-1.0 ȝm. As previously reported by our group [10] , the uniform-sized beads can be well dissolved in the polymeric ISE membrane, which could cause more binding sites available in the membrane and lower membrane impedance. Indeed, the membrane ISE prepared with the uniform clenbuterol MIP beads showed a shorter response time and lower noise levels.…”

Potentiometric sensor for determination of neutral bisphenol A using a molecularly imprinted polymer as a receptor

“…However, very few ISEs have been developed for direct recognition of neutral species [2]. In recent years, it has been found that undissociated neutral phenols could generate anionic potential responses using poly(vinyl chloride) (PVC) liquid membranes doped with lipophilic nitrogen-containing compounds and metal porphyrins [3][4][5].…”

Molecularly imprinted nanoparticles based potentiometric sensor with a nanomolar detection limit

“…The resulting polymer was dried for 10 h in vacuum at 50 • C. Non-imprinted polymer (NIP) was prepared under identical conditions except for omission of the template. Traditional MIP microbeads were prepared according to the precipitation method described before [16].…”

“…As generic and highly successful approaches to chemical sensing, potentiometric sensors have shown to be very promising for trace-level environmental and biological measurements [10,11]. Nowadays, potentiometric sensors based on MIPs have been successfully developed for determination of anions, cations and neutral species [12][13][14][15][16]. However, it should be noted that most of the MIPs based potentiometric sensors developed so far have poor detection limits in the micromolar range, which are unsuitable for trace-level measurements, especially with high levels of electrolyte background.…”