Study On Determination Of Ethyl Carbamate In Wine

Ethyl carbamate, a pluripotent carcinogen, has resulted in an increased incidence of lung, lymphocytic leukemia, liver, and melanotic tumors of the skin, which was first demonstrated in 1943. The International Agency for Research on Cancer (IARC) has classifed ethyl carbamate as a Group 2B, possibly carcinogenic to humans. Most fermented foods and beverages, including wine, contain trace amounts of ethyl carbamate. Health Protection Branch of Canada set the upper limit of 30μg/L ethyl carbamate in table wine; and the U.S. Food and Drug Administration has established a voluntary target for ethyl carbamate of 15μg/L for table wine≤14% alcohol by volume starting with the 1988 harvest.The purpose of the paper was to set up the standard method for measuring ethyl carbamate in table wine. Furthermore, based on the standard method, the quick and nondestructive method of determining ethyl carbamate in wine was studied using partial least square - fourier transform - near infrared spectroscopy (PLS– FT -NIRs).The paper mainly describes the sample-pretreated methods for analyzing ethyl carbamate in table wines in combination with a gas chromatographic/mass spectrometric (GC/MS) system, and n-propyl carbamate used as the internal standard. Parameters were optimized of the sample-pretreated methods including liquid/liquid extraction, solid phase extraction, solid phase microextraction and solid/liquid extraction. The results were as follows: The parameters of the liquid/liquid extraction method were optimized: the pH of the samples was natural pH, KCl 16 g (40%), dichloromethane 300mL. The limits of detection were 8μg/L.The recoveries and the precision was 76.56%-80.39%, the relatively standard deviation (RSD) measured on the same day was 4.42-9.82%, the relatively standard deviation measured the next day was 6.94~10.36% Liquid/liquid extraction method used for determination of ethyl carbamate in table wines dispenses with expensive instruments, however it has drawbacks: severe emulsification; the large amounts of organic solvents used, resulting in a large volume of waste; the low precision and accuracy due to manual concentration steps.The optimized parameters of the solid phase microextraction of table wine were: sample pH was 10, and 9.0 mL sample and 2.0-2.5 g (20-25%) NaCl (pH 10.0) were added to the vial;the sample vial was shaken for 30min at 40℃at 800 rpm in the agitator for equilibration;A 70μm CW/DVB fiber was inserted into the headspace for 35min at 40℃, then the fiber removed from the sample vial and inserted into the injection port of the GC for 10min. Under this extraction conditions, the recoveries and the presision were 76.00-84.80%, and 6.62~10.95%, respectively. The limits of detection were 8.0μg/mL. The solid phase microextraction technique was successfully applied to determine the ethyl carbamate levels in table wines, and it allows the extraction and concentration to be focused in a single step. The extraction method was rapid and simple, and without the need for any organic solvent, and it was an environmental protecting extraction method. But it has low precision and accuracy due to unstable fibers.The parameters of the solid phase extraction method were: the pH of the samples was natural pH, dichloromethane 175 mL. The recoveries and the precision was 85.76~102.82%, the relatively standard deviation (RSD) measured on the same day was 4.22~8.20%, the relatively standard deviation measured the next day was 4.60~10.13%. respectivly. The limit of detection was 3.0μg/mL. And the optimized parameters of the solid/liquid extraction method were: the pH of the samples was natural pH, dichloromethane 70 mL. The recoveries and the precision was 82.67~93.39%, the relatively standard deviation (RSD) measured on the same day was 2.91~6.67%, the relatively standard deviation measured the next day was 4.60~10.13%. The limits of detection were 2.0μg/mL.Both solid/liquid extraction and solid phase extraction methods provided good recovery and reproducibility. There was no significant difference between the two methods (p<0.05). Solid phase extraction method was recommended by OIV, but in the OIV method, anhydrous ethanol, one of the reagents, contained ethyl carbamate in itself. Therefore, there was drawback in this method. Furthermore, comparison with the solid phase extraction method, solid/liquid extraction method was less cost, environmental protecting, fast and simple. In the study, the solid/liquid extraction method was selected as the standard method to extract the ethyl carbamate in table wines.Solid/liquid extraction method in combination with GC/MS was applied to analysis for ethyl carbamate in 50 Chinese table wine samples. Based on the data, A PLS– FT -NIRs model was set up. The correlation coefficients (R2) and the root mean square error of prediction (RMSEP) were 0.9777 and 1.14 mg/L, respectively, and its dimension of principal component was 2; In the validation and evaluation experiment, the correlation coefficient (R2) and the root mean square error of prediction (RMSEP) of the forecast and the real value was 0.9578 in 10 samples; the relative standard deviation (RSD) of precision and stability in model forecast was 0.88%. The developed standard method of determination of ethyl carbamate in table wines was simple, fast, reproducible and accurate, and the method could be applicable for routine determination of ethyl carbamate in table wines. The method using PLS– FT–NIRs could be applicable for quick and nondestructive determination of ethyl carbamate in table wines.