Development of a carbon ceramic electrode for determination and separation of tert-Butylhydroquinone in Edible Oils using molecular imprinted Polymer

Tert-buthyl hydroquinone (TBHQ), a phenolic antioxidant used as a food additive, and its metabolite 2-tert-butyl-1,4- benzoquinone (TBQ) was cytotoxic in human monocytic leukemia U937 cells. Both compounds induced caspase activity towards DEVD-MCA as a substrate and the cleavage of poly (ADP-ribose) polymerase in cells. The inhibition of monooxygenation activity was accompanied by redox cycling due to the tert-butylquinone produced during BHA metabolism, as measured by increased NADPH and oxygen consumption or hydrogen peroxide and superoxide anion production [1]. Accordingly, there is a need for a method to assess and determination of particular drug. Electrochemical sensor may serve the purpose due to its relative simplicity, selectivity, low-cost and fast response time [2]. On the other hand, molecularly imprinted polymers (MIPs) are tailor made materials with selective recognition properties toward a chosen guest molecule or related compounds similar to that displayed by antibodies but without their experimental restrictions [3]. Molecularly imprinted polymer (MIP) were synthesized of TBHQ (template), methacrylic acid as functional monomer, ethylene glycol dimethacrylate as cross-linking agent and 2,20- azobisisobutyronitrile as initiator . Then, the MIPs were used to modify the carbon ceramic paste electrode (CCE). In the present study, an electrochemical nanosensor based on molecular imprinted polymer has been designed and developed for separation and determination of TBHQ antioxidant in edible oil. The MIP synthesized by Methacrylic acid as a functional monomer, Ethylene glycol dimethacrylate as cross linker, 2,2- azobis(2-methyl propionitrile) as initiator and TBHQ has been used as template. In the next stage Multiwall carbon Nano tube, Graphite, MIP and SiO2 solution used for making carbon ceramic 394 electrode. The effect of different parameters such as, solution temperature and time for preconcentration of TBHQ on electrode surface, also MIP and MWCNT amounts in preparation of electrode were investigated and optimized with statistical method of the Central Composite Design (CCD). Optimized condition determined as MWCNT=7.0 mg, MIP= 11 mg, Temp=32 °C and time of 12 minutes. Under optimal experimental conditions, DPVs of MIP/MWCNT/CCE was recorded to estimate the lower limit of detection and the linear range of TBHQ. As expected, the oxidation peak current increased upon the increase of TBHQ concentration. Fig 1 clearly indicates that the plot of the reduction peak current against the GA concentration was linear in the range of 20–950 μM. According to the method mentioned in Skoog et al. (1998), the lower detection limit, Cm, was calculated 7.1 μM by using the equation Cm=3sbl/m, where sbl is the standard deviation of the blank response and m is the slope of the calibration plot (0.0013 μA μM). The average voltammetric peak current and the precision estimated in terms of the coefficient of variation for repeated measurements (n = 15) of 7.1 μM TBHQ at the MIP/MWCNT/CCE were 0.295 ± 0.007 μA and 2.4 %, respectively. Finally, performance of proposed procedure was evaluated to separation and determination of TBHQ in different edible oil Table 1. 395 Fig 1. Differential pulse voltammograms of MIP/MWCNT/CCE in a 0.1 M phosphate-buffered solution (pH 7.0) containing different concentrations of TBHQ. Insets show the plots of the electrocatalytic peak current as a function of TBHQ concentration in the range of 20-950 μM. Table 1: Determination and recovery results of TBHQ in edible oil using DPV calibration plots and with the nanosensor (MIP–MWCNT–CCE) Sample Initial found (μM) Added (μM) Found (μM) Recovery (%) Sesame Oil * 40.0 40.5 101.25 60.0 59.8 99.66 80.0 81.2 101.5 corn oil 124.8 40.0 163.9 99.45 60.0 185.2 100.2 80.0 203.12 99.1 Sunflower oil 177.75 40.0 216.54 99.4 60.0 240.1 101.25 80.0 253.64 98.4 Colza Oil 276.5 40.0 319.2 100.8 60.0 333.6 99.13 80.0 365.8 102.6