Design and Development of a Nano sensor Modified by Molecularly ImprintedPolymers for Determination of Thiourea at Industrial Media

Thiourea (TU) as an organic additive is most commonly used in industrial processes of copperelectro refining from acidified copper sulfate solutions. TU affects the structure of depositedcathodes via the mechanism of electrolytic reduction processes. Smooth and pure copper isobtained in case the reagent is in a proper concentration. An insufficient amount of a smoothingreagent has an equally detrimental effect that causes the nodulation phenomenon of the cathode.Since TU is consumed during electro refining by co-deposition with copper, it must be added tothe electrolyte in a continuous way. Therefore, it is desirable to be able to measure the reagentconcentration in the electrolyte [1]. In food industries, TU is known as a toxic and hazardous, andthese effects seem to arise from a disturbance of carbohydrate metabolism that may be harmfulfor humans. Furthermore, TU has also been screened as allergenic and carcinogenic factors [2].Different analytical techniques such as UV–Vis spectrophotometry, UV reflectance spectrometry,infrared spectrometry, chemiluminescence, Raman spectroscopy, chromatography andelectrochemical methods [3] have been reported for the determination of TU in various samples.Electrochemical methods are suitable for determination of low levels of TU because of their highsensitivity and selectivity and inexpensive instrumentation. Development of various modifiedelectrodes to achieve higher selectivity and sensitivity has been of interest, but there are fewreports so far on the determination of TU using modifiers. Moreover, molecularly imprintedpolymers (MIPs) are tailor made materials with selective recognition properties toward a chosenguest molecule or related compounds similar to that displayed by antibodies but without theirexperimental restrictions [4]. The MIPs were used to modify the carbon ceramic paste electrode (CCE). In the present study, an electrochemical nanosensor based on MIP has been designed anddeveloped for separation and determination of TU in industrial waste of Sarcheshmeh copper Inc.Co. The MIP synthesized by Methacrylic acid as a functional monomer, Ethylene glycoldimethacrylate as cross linker, 2,2-azobis(2-methyl propionitrile) as initiator and TU has beenused as template. In the next stage Multiwall carbon Nano tube, Graphite, MIP and SiO2solutionused for making carbon ceramic electrode. The effect of different parameters such as, solution pHand time for pre-concentration of TU on electrode surface, also MIP and MWCNT amounts inpreparation of electrode were investigated and optimized with statistical method of the RespondSurface Methodology (RSM). Optimized condition determined as MWCNT=3.3 mg, MIP= 12.3mg, pH=8.0 and time of 26 min. Under optimal experimental conditions, DPVs ofMIP/MWCNT/CCE was recorded to estimate the lower limit of detection and the linear range ofTU. As expected, the oxidation TU signal increased upon the increase of TU concentration. Fig 1clearly indicates that the plot of the reduction peak current against the TU concentration waslinear in the two range of 0.05–5.0 nM and 50 -1100 nM. According to the method mentioned inSkoog et al. (1998), the lower detection limit, Cm, was calculated 0.12 pM by using the equationCm=3sbl/m, where sbl is the standard deviation of the blank response and m is the slope of thecalibration plot (0.2883 mA nM). The average voltammetric peak current and the precisionestimated in terms of the coefficient of variation for repeated measurements (n = 15) of 0.12 pMTU at the MIP/MWCNT/CCE were 0.295 ± 0.007 mA and 2.4 %, respectively.Finally, performance of proposed procedure was evaluated to separation and determination of TUin industrial electrolyte of Sarcheshmeh copper Co. (Table 1).

کلیدواژه ها:

Thiourea ، Determination ، Molecular Imprinted Polymer ، Nanosensor ، CarbonCeramic Electrode