Validation (in-house and collaboratory) of the quantification method for ethyl carbamate in alcoholic beverages and soy sauce by GC-MS.

A method for ethyl carbamate (EC) determination in alcoholic beverages and soy sauce was developed by GC-MS. We adopted the diatomaceous earth solid-phase extraction (SPE) column and elution solvent of ethyl acetate/diethyl ether (5:95 v/v) for sample cleaning. The in-house validation showed the limit of quantification (LOQ) was 5.0 µg/kg. In the accuracy assay, the total average recovery for was 96.7%. The relative standard deviations (RSDs) were <5%. Subsequently, a collaborative trial was organized for the further validation. The RSDs for repeatability and reproducibility were 1.2-7.8% and 2.3-9.6% respectively. It indicated that the present method performed well in different laboratories.

[Study on content of ethyl carbamate in yellow rice wine and its change in Zhejiang province].

OBJECTIVE: To understand the content status of ethyl carbamate (EC) in yellow rice wine and the changes in storage period and shelf life in Zhejiang province. METHODS: A total of 475 samples of yellow rice wine purchased randomly from supermarkets and food stores in Zhejiang province during 2008-2012, and 49 samples collected from manufacturers were measured for EC content. The sample collected from manufacturers by filter sterilization was placed at 4 °C, room temperature and 37 °C for 400 d, respectively;a bottled wine and a wine in bag were bought from market were placed for 400 d in room temperature to conduct shelf life storage test, and measure the content in every point in 2011. The EC of the samples was determinated by gas chromatography-mass spectrometry after the samples were diluted with D5-EC isotope dilution technique, and purified by alkaline diatomite solid phase extraction column. RESULTS: The overall detection rate of EC was 99% (472/475) in yellow rice wine of Zhejiang province in 2008-2012, the median value was 70-112 µg/kg, the 90th percentile was 190-333 µg/kg, the 95th percentile was 214-393 µg/kg, and the maximum value was 430-515 µg/kg. The content of EC was increased gradually along with the increasing of storage age in commercially yellow rice wine, and the average content of EC were positively correlated with storage age(r = 0.988). The contents of EC in yellow rice wine after sterilization increased from 74 µg/kg to 86 µg/kg, 127 µg/kg and 509 µg/kg at 4 °C, room temperature and 37°C, respectively for 400 d storage, the differences had statistical significance (F = 14.73, P < 0.01). The content of EC in yellow rice wines in shelf life, which stored in room temperature with bottle and bag package, was decreased slightly with increasing storage time in the beginning, from 215 to 184 µg/kg and 196 to 158 µg/kg, respectively, and increased again with increasing storage time after 250 d, with 252 µg/kg and 210 µg/kg in bottle and bag package after 400 d, respectively, the differences had statistical significance (Z = 2.37, P < 0.05). CONCLUSION: EC is widespread in rice wine, the content of EC was correlated with storage time and temperature.

[Detection of methyl carbamate and ethyl carbamate in yellow rice wine by gas chromatography-mass spectrometry].

OBJECTIVE: To establish the method of simultaneous determination of methylcarbamate (MC) and ethylcarbamate (EC) in yellow rice wine by gas chromatography-mass spectrometry (GC/MS). METHODS: MC and EC in yellow rice wine were derived by 9-xanthydrol, and then the derivants were detected by GC/MS; and quantitatively analyzed by D5-EC isotope internal standard method. RESULTS: The linearity of MC and EC ranged from 2.0 µg/L to 400.0 µg/L, with correlation coefficients at 0.998 and 0.999, respectively. The limits of quantitation (LOQ) and detection (LOD) were 0.67 and 2.0 µg/kg. When MC and EC were added in yellow rice wine at the range of 2.0-300.0 µg/kg, the intraday average recovery rate was 78.8%-102.3%, relative standard deviation was 3.2%-11.6%; interday average recovery rate was 75.4%-101.3%, relative standard deviation was 3.8%-13.4%. 20 samples of yellow rice wine from supermarket were detected using this method, the contents of MC were in the range of ND (no detected) to 1.2 µg/kg, the detection rate was 6% (3/20), the contents of EC in the range of 18.6 µg/kg to 432.3 µg/kg, with the average level at 135.2 µg/kg. CONCLUSION: The method is simple, rapid and useful for simultaneous determination of MC and EC in yellow rice wine.

[The determination of phthalic acid esters in edible vegetable oils by gas chromatography-mass spectrometry].

OBJECTIVE: We aimed to establish a quantified method for the 17 phthalate acid esters (PAE) in edible vegetable oil by gas chromatography-mass spectrometry (GC-MS) with the pretreatment of acetonitrile extraction and silica/N-(n-propyl)ethylenediamine (silica/PSA) mixed solid phase extraction column and evaluated the PAE of 25 edible oil samples from supermarkets in Hangzhou city. METHODS: The internal standard solution (D4-DEHP) was added in edible vegetable oil sample. The analytes were extracted by acetonitrile with 1 min vortex, and centrifuged at 3050×g for 5 min. The supernatant was then cleaned with silica/PSA column, and eluted with acetonitrile. The elution was dried with N2 flow at 50°C and diluted to 1.0 ml with hexane. Then, 17 PAE were tested by GC-MS and quantified with internal standards. The repeatability and sensitivity of the assay were evaluated. PAE were then determined in 25 plastic buckets of edible vegetable oil from supermarkets in Hangzhou city. RESULTS: By the quantification of internal standard of D4-DEHP, a good linearity range of related 17 PAE was observed. The correlation coefficient was 0.994-1.000 and the standard lowest quantified level was 0.05-0.15 µg/ml. The spiking recoveries of 17 PAE were 78.3%-108.9% with the RSD of 4.3%-12.1% (n=6). The method detection limits were 0.1-0.2 mg/kg. In 25 plastic buckets of edible vegetable oil from Hangzhou, DMP, DEP, DIBP, DBP and DEHP were detected at the range of <0.1-1.8 mg/kg and the detection rates were 12% (3/25), 24% (6/25), 100% (25/25), 96% (24/25) and 100% (25/25), respectively. Other 12 PAE was not detected. For DBP with the level of <0.1 to 1.3 mg/kg, the results of 16% (4/25) samples exceeded the regular migrating limit of 0.3 mg/kg. For DEHP of <0.2-1.8 mg/kg, the data of 12% (3/25) samples were beyond the regular migrating limit of 1.5 mg/kg. CONCLUSION: The pretreatment by silica/PSA mixed solid phase extraction column can satisfy the PAE determination requirements in edible vegetable oils. The DMP, DIBP, DEP, DBP and DEHP were detected from the survey of 25 edible oil samples in Hangzhou city.

[Survey and analysis of ethyl carbamate in commercial fermented foods in Hangzhou in 2010].

OBJECTIVE: To observe the ethyl carbamate concentrations in different commercial fermented foods in Hangzhou in 2010. METHODS: In 2010, 237 commercial fermented food samples of eight categories, including yellow wine, white spirit, wine, beer, cooking wine, sauce, vinegar and fermented bean curd, were purchased from 3 different size markets respectively in Hangzhou. The ethyl carbamate was measured by gas chromatography-mass spectrometry in selection ion mode, after the samples were coupled with D5-ethyl carbamate, and purified by diatomite solid phase extraction column. RESULTS: The results showed that ethyl carbamate was detected in all samples analyzed (100%) with the range from 2.0 µg/kg to 515.0 µg/kg. The ethyl carbamate average (median) levels in 8 food categories were descending with fermented red bean curd (182.2 µg/kg (161.2 µg/kg)), yellow wine (159.6 µg/kg (121.0 µg/kg)), cooking wine (86.8 µg/kg (95.6 µg/kg)), white spirit (72.0 µg/kg (60.5 µg/kg)), soy sauce (47.2 µg/kg (40.7µg/kg)), vinegar (26.7 µg/kg (31.8 µg/kg)), wine (15.7 µg/kg (16.8 µg/kg)) and beer (2.2 µg/kg (2.3 µg/kg)). CONCLUSION: The ethyl carbamate was detected in all fermented foods in Hangzhou in 2010, and the levels of ethyl carbamate in red bean curd and yellow wine were higher than others.