Chloropropanol is a kind of toxic carcinogenesis generated in chemical production of soy sauce. It also has inhibitory effect on the production of male hormones which decrease the reproductive ability. It is greatly harmful to human body. Daily common three kinds are as following: 1-chloro-2-propanol (ClCH2CHOHCH3); 3-chloro-1,2-propanediol (3-MCPD) and 1,3- dichloro-2- propanol (1,3-DCP).
Accurately weigh 0.1 g chloropropanols standard substance in to100 mL volumetric flask, constant volume to scale by ethyl acetate and get 1 mg/mL stock solution. Gradually dilute the stock solution with acetone to get 1 μg/mL standard working solution. Weigh 290 g sodium chloride, add water to dissolve and dilute to 1000 mL, and then ultrasonic for 20 min
Weighs 2.5 g soy sauce directly loads to the Cleanert MCPD solid phase extraction column, static balance for 10min, wash the column with 15 mL ethyl acetate and collect the eluent. Nitrogen blow the eluent to nearly dry (not dry completely) at 35 °C. Add 2 mL n-hexane, shake, quickly add 50 μ L seven fluorine butyl acyl imidazole, tighten the sample bottle, vortex for 20 seconds, put the sample bottle into 70℃ thermotank to react for 30 min, take out and cool to room temperature, add 2 mL Saturated sodium chloride solution into sample bottle, vortex 1 min, stewing for 2 min, taking the upper organic phase to another clean sample bottle, repeat 1 times washing operation to remove impurities. After removing water with a small amount of anhydrous Na2SO4, transfer the organic phase to injection sample bottle for GC-MS detection.
Chromatographic column: DA-5MS 30 m × 0.25 mm × 0.25 μm
Injection port: 230 °C, splitless injection
Temperature programming: 50 °C (1 min) 2 °C /min 82 °C
Injection volume: 1 μL
Flow velocity: 1 mL/min
Interface temperature: 250 °C
Ionization mode: EI
Ionization energy: 70 eV
Solvent delay: 7 min
Ion source: 230 °C
Quadrupole: 150 °C
Detection mode: selective ion detection;
SIM ion: 253/275/289/291/453
Results and Discussion
Accurately weigh 6 pieces of the soy sauce, add 1 μg/mL standard solution into five pieces respectively. Purify derivative 6 samples according to the processing method above and get chromatogram of spiked soy sauce sample and chromatogram of soy sauce sample as shown in Figure 2 and Figure 3.
Figure1 Chromatogram of standard solution (concentration of 50 ng/mL)
Figure 2 Chromatogram of spiked soy sauce sample(concentration of 50 ng/mL)
Figure 3 Chromatogram of soy sauce sample
Table 1 Recovery rate and precision
Average recovery rate/%