Influence of Methacrylic-Acrylic Copolymer Composition on Plasticiser-free Optode Films for pH Sensors

Abstract

Abstract:In this work we have examined the use of plasticiser-free polymeric films incorporating a proton selective chromoionophore for optical pH sensor. Four types of methacrylic-acrylic copolymers containing different compositions of n-butyl acrylate (nBA) and methyl methacrylate (MMA) were synthesised for use as optical sensor films. The copolymers were mixed with appropriate amounts of chromoionophore (ETH5294) and a lipophilic salt before spin coated on glass slides to form films for the evaluation of pH response using spectrophotometry. Co-polymer films with high nBA content gave good response and the response time depended on the film thickness. A preliminary evaluation of the optical films of high nBA content with pHs from 2 -14 showed distinguishable responses from pH 5 -9. However, the adhesion of the pH sensitive film was good for copolymers with higher content of MMA but not for films with high nBA.

A Urea Biosensor from Stacked Sol-Gel Films with Immobilized Nile Blue Chromoionophore and Urease Enzyme

“…The behaviour of the immobilized chromoionophore towards pH changes is close to those observed in similar sol-gel materials reported [8] or that immobilized in plasticizer-free polymers such as methacrylic-acrylic membranes [10]. The linear response range of the pH sensitive sol-gel layer is from pH 4.28 to 10.36 (y = 0.0219x - 0.0782, R 2 = 0.9549) (Figure 2).…”

“…To test the response of the pH, cuvettes containing the a sensing film were first filled with 2 mL of the test solution and then placed in a spectrophotometer with the sensing film nearer to the incoming light source. These films were first scanned in the wavelength range of 400-800 nm to demonstrate the presence of peaks at 550 nm (deprotonation), 600 and 650 nm (protonation) [10]. Absorption peak of 550 nm was selected for optode studies because it was separated from the other two peaks.…”

<strong>Polyaniline-Coated Polysulfone Membranes as Flexible Optical pH Sensors</strong>

“…Polymeric membranes have been widely utilized as immobilization matrices for various types of sensors including optical chemical sensors [1,2], biosensors [3,4] potentiometric sensors [5][6][7], and amperometric sensors [8,9]. Solid polymeric membrane supports offers advantages such as fast response time, minimal calibration requirement, flexibility, low cost and possibility for deposition into various types of substrates [10]. The performance of polymeric membranes can be enhanced by surface functionalization/ grafting with hydrophilic/ hydrophobic sites for obtaining maximum interaction with specific analyte [6,11].…”

Full-range optical pH sensor based on imaging techniques

“…Different types of immobilization techniques for pH indicating dyes have been used [9], including (a) dye entrapment in different materials such as cellulose acetate [10,11], sol-gel [12], PVC [7], methacrylic-acrylic copolymers [13] and different composites like SiO 2 /ZrO 2 -organic polymer (styrene/methyl methacrylate copolymer or Nafion) [14], (b) retention of dye by ion-exchange materials such as Amberlite XAD-2 resin [15] or Dowex l-X10 resin [16], in some instances including the ionexchanger containing dyes in polymeric encapsulated membranes using PVC [17], (c) adsorption of the dye on materials such as non-ionic styrene/divinylbenzene copolymer [18], polyester/lycra blends textile [19], cellulose [20], cellulose acetate [21], or polymer track membranes combining retention in surface and bulk [22], (d) covalent binding of dye by different synthetic strategies to form microparticles or membranes, in some cases formed on glass fibre, using different polymers such as polyacrylamide [8,23], triacetylcellulose [24], cellulose acetate [25,26], agarose [27] or polyamide [28], among others, (e) polymerization of monomers to prepare both membrane and dye, as with aniline [29] or pyrrole [30].…”

“…Thus, the dynamic working range for pH optical sensors is limited to a few pH units (2-3) [13] and even shorter if the linear relationship in the middle of the sigmoidal response is used. This short range is one of the main drawbacks of these optical sensors for pH, along with their nonlinear response, which requires different sensing membranes to cover the whole pH range.…”