An Optical Sensor Based on Polyvinyl Benzyl Malonate Cross-Linked with Divinyl Benzene Dispersed in a Hydrogel Membrane for Detection of Some Heavy Metals

Imad Odeh, Ziad Shakhsher, Suha Jaber, Mahmood Khateeb, Fuad Al-Rimawi

Faculty of Science and Technology, Al-Quds University, East Jerusalem, Palestine.

DOI: 10.4236/ajac.2012.34038                

Abstract

In previous work we have developed a dicarboxylate functionalized polymer that demonstrated chemical sensing. It showed good response to pH changes as well as to varying concentrations of copper and calcium ions. Our recent in-vest- tigations showed interesting results upon testing the functionalized sensing polymer on heavy metals. This sensor is composed of microspheres of polyvinyl benzyl malonate lightly-cross-linked with divinyl benzene dispersed in a hydrogel membrane. The response of the optical sensor is based on the interaction between the metal cations with the deprotonated functional group. The polymer, thus, undergoes shrinking as a result of neutralization of adjacent negative charges on the back-bone of the polymer. This causes significant changes in the optical properties of the sensing element. The optical changes were measured as absorbance vs. wavelength as the sensing membrane is exposed to solutions of varying concentrations of heavy metal ions. The sensor showed significant increase in absorbance up to a concentration of 5 × 10^-3 M to the following metal ions: Ni²⁺, Zn²⁺, and Cd²⁺. Furthermore, the studied capacity of the derivatized microspheres showed close values to Ni²⁺, Zn²⁺, Cd²⁺ (1.20, 1.09, 1.08 mmol/g respectively). These kinds of properly functionalized polymers appear to be suitable, versatile sensing elements for the detection of low concentrations of heavy metal ions. In addition, all of the tested heavy metals showed a similar value of the equilibrium formation constant, (log K_f1 is 2.63). In contrast, the sensor showed no significant response to varying concentrations of K+ and Mg²⁺ metal ions.

Keywords

Shrinking Microsphere Polymer; Polyvinylbenzylmalonate; Optical Chemical Sensors; Heavy Metal Sensing; Equilibrium Formation Constant

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Z. Shakasher, I. odeh and S. Jaber, “An Optical Chemical Sensor Based on Swellable Dicarboxylate Functionalized Polymer Microspheres for pH Copper and Calcium Determination,” Mikrochim Acta, Vol. 144, No. 1-3, 2004, pp. 147-153. doi:10.1007/s00604-003-0077-2
[2]	M. T. V. Rooney and W. R. Seitz, “An Optically Sensitive Membrane for pH Based on Swellable Polymer Microspheres in a Hydrogel,” Analytical Communications, Vol. 36, No. 7, 1999, pp. 267-270. doi:10.1039/a902183c
[3]	W. R. Seitz, M. T. V. Rooney, E. W. Miele, H. Wang, N. Kaval and L. Zhang, “Derivatized, Swellable Polymer Microspheres for Chemical Transduction,” Analytica Chemica Acta, Vol. 400, No. 1, 1999, pp. 55-64.
[4]	I. Oehme and O. S. Wolfbeis, “Optical Sensors for Determination of Heavy Metal Ions,” Mikrochim Acta, Vol. 126, No. 3-4, 1997, pp. 177-192. doi:10.1007/BF01242319
[5]	M. F. McCurley and W. R. Seitz, “Fiber Optic Sensor for Salt Concentration Based on Polymer Swelling,” Analytica Chemica Acta, Vol. 249, No. 2, 1991, pp. 373-380. doi:10.1016/S0003-2670(00)83009-3
[6]	Z. Zhang, Z. Shaksher and W. R. Seitz, “Aminated Polystyrene Membranes for a Fiber Optic pH Sensor Based on Reflectance Changes Accompanying Polymer Swelling,” Mikrochim Acta, Vol. 121, No. 1-4, 1995, pp. 41-50. doi:10.1007/BF01248239
[7]	Z. Shaksher, W. R. Seitz and K. D. Legg, “Single Fiber- Optic pH Sensor Based on Changes Accompanying Polymer Swelling,” Analytical Chemistry, Vol. 66, No. 10, 1994, pp. 1731-1735. doi:10.1021/ac00082a021
[8]	Z. J. Zhang, Y. Zhang, M. Wangbai, R. Russell, Z. M. Shaksher, C. L. Grant, W. R. Seitz and D. C. Sundberg, “Poly(Vinyl Alcohol) as a Substrate for indicator Immobilization for Fiber-Optic Chemical Sensors,” Analytical Chemistry, Vol. 61, No. 3, 1989, pp. 202-205. doi:10.1021/ac00178a003
[9]	T. Hirotsu, S. Katoh, K. Suga-saka, M. Sakurgi, K. Ichimura, Y. Suda, M. Fujishima, Y. Abe and T. Misonoo, “Synthesis of Dihydroxamic Acid Chelating Polymers and the Adsorptive Property for Uranium in Sea Water,” Journal of Polymer Science Part A: Polymer Chemistry, Vol. 24, No. 8, 1986, pp. 1953-1966.