[Determination of 3-monochloropropane-1,2-diol in grease food by solid phase extraction-derivatization-gas chromatography-mass spectrometry].

OBJECTIVE: To establish the method of determination of 3-monochloropropane-1,2-diol( 3-MCPD) in grease food by gas chromatography-mass spectrometry( GC-MS). METHODS: 3-MCPD in grease food represented by bean paste was extracted by ultrasound,purified by alkaline earth solid phase extraction column,derivatived using phenylboronic acid( PBA) and detected by GC-MS. RESULTS: The linearity of 3-MCPD ranged from 1-100 ng/mL,with correlation coefficient at 0. 9993.The limits of quantitation( LOQ) in soy sauce,bean paste,pepper oil were 0. 6,0. 5 and7. 0 µg/kg and limits of detection( LOD) were 1. 9,1. 6 and 18. 8 µg/kg,respectively.Average recovery rate and relative standard deviation was 78. 3%-106. 7% and 1. 9%-11. 6%( n = 6), when 3-MCPD was added in grease food at 2. 5-1000 µg/kg. CONCLUSION: The method has good purification effect and the detection sensitivity and accuracy,and can be used for the determination of 3-MCPD in grease food.

Aluminium in food and daily dietary intake assessment from 15 food groups in Zhejiang Province, China.

Aluminium was measured in 2580 samples of 15 food groups and dietary exposure was estimated. Samples were purchased and analysed during 2010 to 2014. High aluminium levels were found in jellyfish (mean 4862 mg/kg), laver (mean 455.2 mg/kg) and fried twisted cruller (mean 392.4 mg/kg). Dietary exposure to aluminium was estimated for Zhejiang residents. The average dietary exposure to aluminium via 15 food groups in Zhejiang Province was 1.15 mg/kg bw/week, which is below the provisional tolerable weekly intake of 2 mg/kg bw /week. Jellyfish is the main Al contributor, providing 37.6% of the daily intake via these 15 food groups. This study provided new information on aluminium levels and assessment of aluminium (Al) dietary exposure in Zhejiang Province of China.

Determination of Ethyl Carbamate in Chinese Yellow Rice Wine by Diatomaceous Earth Extraction and GC/MS Method.

A sensitive and rapid analytical method based on alkaline diatomaceous earth extraction followed by GC/MS was developed for the quantitative determination of the toxic contaminant ethyl carbamate (EC) in yellow rice wines. The optimal extraction conditions were investigated. With the application of diatomaceous earth extraction, the damage of organic acids to the capillary column was greatly reduced. By using d5-EC as an internal standard for quantitative analysis of EC, the linearity of the calibration curves was good between 10 and 1000 ng/mL. The LOD and LOQ were 1.7 and 5.0 µg/kg, respectively. The spiked level of EC was 5.0-300 µg/kg, and the average recovery of the spikes was between 78.4 and 98.2%, with an RSD between 4.3 and 8.3%. Upon validation by five laboratories when spiked with 50, 100, and 300 µg/kg, the average respective recoveries were 102.9, 102.2, and 98.7% with a RSD between 0.7 and 8.1%. The validation results demonstrated that the method is fast, simple, selective, and suitable for the determination of EC in yellow rice wines.

Identification of 19 phthalic acid esters in dairy products by gas chromatography with mass spectrometry.

A detection method for 19 kinds of phthalic acid ester compounds analyzed by n-hexane/ether/acetonitrile 1:7:8 v/v/v mixed solvent extraction, quick, easy, cheap, effective, rugged, and safe purification and internal standard method of quantitative gas chromatography with mass spectrometry was established. This method can effectively remove interfering materials, such as lipids, fatty acids, and pigments, from dairy products. The 19 kinds of phthalic acid ester compounds were within a 0.025-0.2 mg/kg range, the recovery rate was 65.2-125.7%, relative standard deviation was 7.9-15.4% (n = 6), and the limit of detection was 0.005-0.02 mg/kg. Concentrations of the 19 kinds of phthalic acid ester compounds ranged between 0.01 and 0.12 mg/kg in ten dairy materials and 20 dairy products. The established method is simple, rapid, accurate, and highly sensitive.

Formation of ethyl carbamate and changes during fermentation and storage of yellow rice wine.

Ethyl carbamate (EC) was analyzed during yellow rice wine production and storage. EC increased slowly during fermentation and rapidly after frying and sterilization. Less amount of EC was formed when cooled rapidly to 30 °C than when cooled naturally. High temperature and long storage time increased EC formation. After 400 days storage, EC increased from 74.0 to 84.2, 131.8 and 509.4 µg/kg at 4 °C, room temperature and 37 °C, respectively, and there was significantly difference between the fried wine and the wine on sale from 2011 (p<0.01). Urea increased during yellow rice wine fermentation and was above 20 mg/kg after the wine was fried; urea contributed to EC formation when the fried wine was cooled slowly. These results indicate that it is necessary for industry to optimize the wine frying conditions, such as temperature, time and cooling process in order to decrease EC formation.

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.

Simultaneous determination of 17 phthalate esters in edible vegetable oils by GC-MS with silica/PSA-mixed solid-phase extraction.

A quantified method for the determination of 17 phthalate esters (PAEs) in edible vegetable oil by GC-MS with the pretreatment of acetonitrile extraction and silica/N-(n-Propyl)ethylenediamine-mixed SPE column was established. By the quantification of internal standard of D(4)-di(2-ethylhexyl) phthalate, a good linearity range of related 17 PAEs was observed. The correlation coefficient was ranged at 0.994~1.000, and the standard lowest quantified level was 0.05~0.15 mg/L. The spiking recoveries of 17 PAEs were 78.3~108.9% with the relative standard deviations of 4.3~12.1% (n = 6). The method detection limits were 0.1~0.2 mg/kg. Meanwhile, PAEs were determined in 30 plastic buckets of edible vegetable oil from supermarkets in Hangzhou city of China. The survey of 30 oil samples showed di(2-ethylhexyl) phthalate (DEHP) had the 100% (30/30) detection rate. The levels of diisobutyl phthalate with 86.7% (26:30), di-n-butyl phthalate (DBP) with 70% (21:30) and diethyl phthalate with 10% (3:30) were detected. It was worth note that DBP with 16.7% (5:30) samples and DEHP with 10% (3:30) samples were beyond the regular migrating limit, which indicated that more attention should be paid to the PAEs in oil with plastic package.

[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.

The simultaneous separation and determination of chloropropanols in soy sauce and other flavoring with gas chromatography-mass spectrometry in negative chemical and electron impact ionization modes.

Both gas chromatography-mass spectrometry in electron ionization (GC-MS-EI) and negative chemical ionization (GC-MS-NCI) modes are reported in this paper for the simultaneous determination of 1,3-dichloropropan-2-ol (1,3-DCP), 2,3-dichloropropan-1-ol (2,3-DCP), 3-chloropropane-1,2-diol (3-MCPD) and 2-chloropropane-1,3-diol (2-MCPD) in soy sauce and other flavoring. D(5)-3-MCPD (for 3-MCPD and 2-MCPD) and d(5)-1,3-DCP (for 1,3-DCP and 2,3-DCP) were used as the deuterium isotopic labelled internal standards. The feasibility of using heptafluorobutyric anhydride modified with triethylamine (HFBA-Et(3)N) as a new derivatization reagent to replace heptafluorobutyrylimidazole (HFBI) is proposed. Liquid/liquid extraction with hexane was introduced for high lipid content samples. A small survey was carried out of soy sauces (103 samples) and instant noodles (45 samples) and the applicability of GC-MS-NCI and GC-MS-EI was assessed in these different matrices.