Research On Analytical Methods Of Ethyl Carbamate

Ethyl carbamate(EC, urethane, H2NCOOC2H5) is a natural by-product in fermented foods and alcoholic beverages produced in the process of fermentation and storage, it was validated that EC could cause cancer in animals. In 2002, the Food and Agriculture Organization of the United Nations(FAO) set international standard of the limit of EC in foods: no more than 20 μg/L. Hence, it is of great importance to rapidly and sensitively detect EC in food and alcoholic beverages. EC is a kind of small molecule, whose relative molecular mass is only 89.09. It has no ultraviolet absorption, amino group connect with the ester group makes the activity of amino group become weak. The unique property of EC makes it’s hard to directly detect it by traditional methods, such as HPLC, UV-vis, et al. Up to now, the most common ways to determine EC in the domestic and overseas were depend on GC-MS, HPLC-MS, HPLC-FLD. Although these methods could detect EC at a high sensitivity, the expensive instruments, high requirements for testers as well as high maintenance costs limited their wide application. In this paper, different detection methods were used to detect EC according to the property of it, they could provide certain technical and theoretical support for rapid and sensitive detection of EC in fermented foods and alcoholic beverages. The main results are as follows:1. We researched on the detection of EC based on surface-enhanced Raman scattering(SERS). Uniform and star-shaped silver nanostars(Ag NSs) were used as a novel SERS substrate to detect EC. In comparison to other plasmonic nanoparticles(NPs), including gold nanoparticles(Au NPs), gold nanostars(Au NSs), and silver nanoparticles(Ag NPs), Ag NSs exhibited best SERS activity. Raman signal of EC at trace level could be enhanced several orders of magnitude with the help of Ag NSs. The Raman intensity of EC linearly increased with the increase of EC concentration in the range from 5.0×10-9 mol/L to 1.0×10-4 mol/L with the limit of detection(LOD) of 1.37×10-9 mol/L(S/N = 3). The standard addition method was employed to detect EC in actual samples by SERS technology, the recoveries ranged from 96.8% to 107.6%, illustrating good performance of the developed Raman sensors with high sensitivity and good practical utility. The approach has the advantages of simple, fast,requiring less amount of sample and with higher sensitivity. The method could provide technical support for determination of EC in alcoholic beverages.2. 2, 3-unsaturated glycoside was synthesized by Ferrier(Ⅰ) rearrangement, EC was used as nucleophile, catalyzed by Samarium trifluoromethanesulfonate(Sm(OTf)3), to acted with 3, 4, 6-Tri-O-benzyl-D-glucal. Fluorometric spectrophotometry was employed to detect the fluorescent intensity of 2, 3-unsaturated glycoside to indirectly determine the concentration of EC. It was found that there was a good linear relationship between the concentration of EC and the fluorescence intensity of 2, 3-unsaturated glycoside in the range from 5.0×10-8 mol/L to 1.0×10-5 mol/L, with a linear correlation coefficient R2 = 0.9939, and LOD was 1.07×10-8 mol/L(S/N = 3). Under the optimized conditions, high performance liquid chromatography(HPLC) was also employed to detect 2, 3-unsaturated glycoside, which would indirectly to detect EC. The HPLC peak area of 2, 3-unsaturated glycoside linearly increased with the increase of EC concentration in the range from 2.0×10-5 mol/L to 2.0×10-4 mol/L(1.7 ~17 μg/m L)with the LOD of 1.6×10-6 mol/L(0.59 μg/m L)(S/N = 3) and the correlation coefficient R2 was 0.9895. Indirectly determination of EC by HPLC method has the advantages of more reliable and has less interference. It could provide certain technical and theoretical support for rapid detection of EC in alcoholic beverages and fermented food.3. Based on the intermolecular hydrogen bonding, a molecularly imprinted polymer(MIP) electrochemical sensor was prepared by sol-gel technology. The following was used as the polymerization mixture: EC as template molecule, tetraethoxysilane(TEOS) as across linker, phenyltrimethoxysilane(PTMOS) with both inorganic and organic functional groups was used as functional monomer. Factors which could affect the properties of EC-MIP sensor, such as elution condition, the amount of template molecule added to the polymerization mixture, adsorption time and elution time were investigated in detail. Cyclic voltammetry(CV) and alternating current(AC) impedance were employed to characterize the EC-MIP sensor. Potassium ferricyanide was used as an electrochemical probe to indirectly detect EC, the change of the relatively current values of potassium ferricyanide linearly increased with the increase of EC concentration in the range from 1.0×10-10 mol/L to 1.0×10-6 mol/L with the LOD of 3.14×10-11 mol/L(S/N = 3), the regression equation was y = 0.8278 + 0.0557 Log C,correlation coefficient R2 was 0.9964. The EC-MIP sensor has the advantages of higher sensitivity, with well selectivity and low cost.