Quantitative Analysis Methods For Determination Of Azodicarbonamide And Semicarbazide In Flour

Azodicarbonamide and semicarbazide are decomposed products of the nitrofuran compounds,they will affect the health of human beings if they stay in the human's blood for a long time.Azodicarbonamide is not only a kind of foaming agent using in industrial production,but also a common food additive.Azodicarbonamide will transform to semicarbazide which has more toxicity after a series of treatments with humidity and heat.At present,azodicarbonamide and semicarbazide have also been found in marine food,eggs and milk more than flour products.The public takes a high significance on the health of human beings,thus to develop the methods of determination of low content of azodicarbonamide and semicarbazide in food is very necessary.In chapter 2,a simple,rapid,accurate and green method combining with high performance liquid chromatography(HPLC)to determinate azodicarbonamide in flour products has been developed.The structures of azodicarbonamide were analyzed by ultraviolet-visible spectroscopy(UV-Vis)and fourier transform-infrared spectrometry(FT-IR).The parameters of this method such as the ratio of mobile phase and the flow rate were optimized.The chemicals used in the experiments were much friendly to the environment.In this method,the linear range of the standard curve of azodicarbonamide is from 0 ?g·m L-1 to 20 ?g·mL-1 and its correlation coefficient is 0.9999 with a perfect linear regression,the detecting limitation(S/N=3)of 0.05 ?g·m L-1,the peaks of HPLC of samples are separated clearly and the recoveries of all the spiked samples range from 94.5% to 105.6% indicating that the method of HPLC is an accurate and sensitive method for azodicarbonamide analysis.In chapter 3,a rapid method for the determination of the semicarbazide in flour based on high performance liquid chromatography-tripe quadrupole tandem mass spectrometry(HPLC-MS)was developed.The influence factors,such as,derivative time,derivative temperature,the pH of the extractant,the different extraction methods and the parameters of instrument,were investigated and optimized.The derivatives from semicarbazide combined with 2-nitrobenzaldehyde,extracted by ethyl acetate and dried by nitrogen.The parameters of HPLC-MS were optimized to determine semicarbazide derivatives and isotope internal standard 15N213C-semicarbazide derivatives.The linear correlation coefficient of the quantitative standard curve was 0.9993.The detection limit was calculated to be 0.4 ?g·kg-1(S/N=3)and the recoveries of this method was from 83.25% to 120.11%.As the result,the proposed method of HPLC-MS was sensitive for quantitative analysis of semicarbazide.In chapter 4,a sensitive method for determination of semicarbazide was developed by differential pulse voltammetry(DPV).Compared with traditional methods such as HPLC-MS and HPLC-FLD,it provides some advantages including using small amount of organic solvents and having cheap price for determination.Accordingly,2-nitrobenzaldehyde was used as an active reagent to react with semicarbazide,the target product was quantitatively analyzed by DPV.A linear relationship was obtained with the peak current and the target product concentration ranging from 0 ?g·L-1 to 100 ?g·L-1(R2=0.999).The detection limit was calculated to be 3.0 ?g·kg-1(S/N=3),which is lower than the determination of semicarbazide by DPV directly.The developed method was successfully applied in determining semicarbazide in flour samples with satisfactory recoveries from 92% to 99%(RSD < 4.3%,n=6),indicating a potential and valuable method for semicarbazide analysis on the spot.