| 3 - chloro - 1,2 - propanediol (3 - MCPD) is one of a group of chemical contaminants known as chloropropanols. Recently, many experts pay more attention to 3 - MCPD because of its wide contamination . According to the Joint FAO/WHO Expert Committee on Food Additives (JECFA) , 3 - MCPD has reproduction toxicity , nerve toxic-ity, and carcinogenisis. JECFA established a provisional maximum tolerable daily intake of 2jxg/Kg bw for 3 - MCPD . 3 - MCPD can be developed in food processing and storage. Levels of 3 - MCPD in acid - HVP and soy sauce are significantly higher than in other foods.At present , Capillary Chromatography and Gas Chromatography with Mass spectrometric detections are adopted to detect 3 - MCPD a-broad. However, researches in this area are scarce in China, and the 3 - MCPD detect method by GC - MS is not yet carried out in Liaoning province.This study was designed to establish analytical method for determination of 3 - MCPD in soy sauce by GS - MS. Basing on the meth-od, we examined 3 - MCPD of soy sauce in market, investigating the contamination of soy sauce by 3 - MCPD and evaluating them. Finally , to provide scientific basis for establishing sanitary standard and inspecting soy sauce.Materials and Methods1. Samples60 soy sauce samples were purchased from supermarket and other retail outlets in Liaoning ,Jilin and Shandong province , where manufactories include Beijing , Shanghai, Guangzhou as well as other twenty - three cities and regions in China.2. Apparatus and reagentsMass spectrometer with gas chromatograph GC - MS Hp - 5972, Hp-5ms,3 -MCPD, Phenylboronic acid,etc.3. Experimental method3. 1 Treatment of samplesAdd 5 ml of sample into 10 ml test tube with cap , thoroughly mix with 1.0ml 25% Phenylboronic acid. Put the tube into constant temperature oven at 90 癈 , react for 20 min. Allow the mixture to cool at room temperature and add 3 ml Skellysolve B. Shake for 1 min, allow the phases to separate. Stand for a "while , then transfer the Skellysolve B phase for GC - MS.3.2 3 - MCPD Standard curveSerial standard solutions were got with concentrations of 0.10, 1. 00,10.00,100.00mg/l, including blank. Derivated standard solutions . Use 1 ul to make standard curve of 3 - MCPD3. 3 Analysis condition of GC - MS3.3.1 Operation conditions for Gas Chromatography Samples were separated on a 30m X 0. 25mmi. d. DB5MS column each with a 0. 25u,m film thickness. GC temperature program: 2min at 100℃;, 10℃/min to 230℃ ,hold for 5min; injections 250℃; Helium carrier at 0. 600ml/min;3.3.2 Operation conditions for MSGeneral: HP 5972; transfer line temp 240℃; electronic ion source; electronic power 70eV; mutiplier voltage 2059V; selected ion monitoring mode m/z147.3.4 DeterminationSamples are to be injected 1ul once using the conditions above. Measure the areas of 3 - MCPD . Draw standard curve. 3 - MCPD is calculated by the external standard method.3.5 Precision and recoverySamples with no 3 - MCPD as background are added 3 - MCPD , undertaken recovery test for 3 times. RSD% represents precision, while P% represents recovery.3. 6 Data processingUse EXCEL and SPSS to analyse data.Results1. Full scan El 3 - MCPD derivatives. Peak of 3 - MCPD occurs at 9. 2 min( retention time) . Diagnostic ion peak is m/z147. Detect soy sauce samples with SIM m/z147.2. Scope, repeatability and limit of detectionWith the concentration ranging from 0. 10 - 100. 00 mg/L, the standard 3 - MCPD has a nice linear relationship with the area ofchromatographic peak, and the correlation index is 0. 999879. The lowest limitation of determination is 0. 09 mg/L. Recovery is 105. 9% , relative standard error is 5.90%.3. SamplesConcentration of 3 - MCPD in samples varys from 0 to 21. 8mg/ L. 90% of soy sauce are in line with national standard ( < 1.0mg/ L). The highest level is about 22 times of the standard. 1.67% of the samples are more than 10 mg/L while 8.3% of samples are between 1...
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