Studies On The Application Of Sensor Technology In Food Security And Environmental Montoring

Ractopamine is one kind of β-agonists which are widely used in livestock and poultryfeed as grow promoters. it can inhibit fat deposition and promote growth and proteingeneration, as well as clenbuterol. COD (Chemical oxygen demand) is widely used as oneof the most common detectable parameters for water quality. It will be very important forwater evaluation and wastewater prevention to master and control COD in time. In thispaper, an electrochemical sensor based on multi-wall carbon nanotubes (MWNT) and anenzyme thermal sensor used for determination of ractopamine and COD were individuallyconstructed.This study consists of the two following partsPart I Enhanced oxidation and detection of ractopamine using carbonnanotube film-modified electrodeObjective: To develop a new electrochemical method for the detection of ractopamine.Methods: In the presence of dihexadecyl hydrogen phosphate (DHP), a muti-walled carbonnanotubes composite film modified electrode for determination of ractopamine wasprepared. The electrochemical behavior of ractopamine on GCE and MWNT/GCE wasstudied. The influences of supporting electrolyte, amount of MWNT, accumulation time and accumulation potential on oxidation peak current of ractopamine were investigated.Results: The linear range is from50μg/L to2mg/L, and the detection limit is20μg/L. Thevalue of relative standard deviation is5.5%for10parallel determinations. Finally, thismethod was used to determine the content of ractopamine in pig liver and meat samples.The recovery is over the range from93.1%to107.2%.Conclusion: It was found that the oxidation signal of ractopamine was greatly increased onthe surface of MWNT film and this method has good accuracy.Part II A novel biosensor based on enzyme thermistor for sensitivemeasurement of CODObjective: To explore a novel methodology for determination of chemical oxygen demand(COD) based on thermal biosensor with a flow injection analysis systemMethods: The ability of this biosensor to detect and monitor COD is demonstrated by theincrease degree of enthalpy change employing thermal signal transduction when sodiumhypochlorite is reacting with the organic matter in water samples. Glycine and sodiumhypochlorite were chosen to be used as standard compound and oxidant, respectively. Themechanism and optimal analytical parameters were studied.Results: The required assay time is5~7min as compared to the2h required for theconventional potassium dichromate method. The linear range is over the range from5to1000mg/L, and the limit of detection is as low as0.74mg/L. Moreover, this methodexhibits high tolerance level to chloride ion. For10mg/L COD standard solution,0.015Mchloride ion has no influence. Finally, the sensor was successfully used to detect the CODvalues of different actual water samples and the results were testified by the standarddichromate method.Conclusion: Determination of COD using thermal biosensor.is feasible.