| It was reported that there is a high contamination level of chloropropanols esters in fatty-foods such as edible oil, which has become the new most concerned food safety issues worldwide in recent years because of its risk to human’s health. There are only reports on 3-MCPD esters exposure assessment by the PMTDI (2 μg/kg bw/d) recommended by JECFA on the basis of the assumption of complete hydrolysis of the 3-MCPD esters to 3-MCPD in vivo. And there are no references reported on the metabolism and transformation of other chloropropanols esters except for 3-MCPD dipalmitate in rats. The main researches are summaried as follows:First, a selective and sensitive ultra-high performance liquid chromatography-triple quadrupole mass spectrometry (UHPLC-MS/MS) method coupled with matrix solid phase dispersion (MSPD) extraction using PSA and C18 powder and integrated the fourteen deuterated internal standards was developed for the direct determination of fatty acid esters of 3-chloro-1,2-propanediol (3-MCPD esters) in edible vegetable oils. Limits of detection (LODs) and limit of quantification (LOQs) of the 3-MCPD esters fell in the range of 0.0001～0.020mg/kg and 0.0004～0.050mg/kg, respectively. The recoveries for the spiked extra virgin olive oils ranged from 94.4% to 108.3%, with the relative standard deviations (RSD) within 10.9%, which showed the present method accurate and sensitive for the detection of the oil sample except for palm oil.Second, an ultra-high performance liquid chromatography-triple quadrupole mass spectrometry (UHPLC-MS/MS) method was developed for the direct determination of fatty acid esters of chloropropanediols (MCPD esters) in the animal tissues and biological fluids. The samples were extracted by acetone and petroleum ether (V:V=1:1) and purified by HLB SPE column, and the purified solution last for the qualitative and quantitative analysis of UHPLC-MS/MS. The LODs and LOQs in animal tissues and blood were in the range of 0.0001-0.030mg/kg and 0.0003～0.100Omg/kg, respectively. The recoveries for the spiked blank samples ranged from 82.8% to 115.6%, with the relative standard deviations (RSD) less than 20.0%, which indicated that the method is sensitive and accurate for the confirmation of MCPD fatty acid ester residues in animal tissue and blood samples.Third, a method for the determination of fatty acid esters of chloropropanols in diet samples by gaschromatography-mass spectrometry (GC-MS) with solid-supported liquid-liquid extraction (SLE) was established. Diet samples were ultrasonically extracted by hexane, followed by ester cleavage reaction with sodium methylate in methanol, and then purified by solid-supported liquid-liquid extraction (SLE) using diatomaceous earth as the sorbent. After derivatization with heptafluorobutyrylimidazole, the analytes were detected by GC-MS and quantified by the four deuterated internal standards. The LODs and LOQs of the four chloropropanols fatty acid esters were 0.002～0.005 mg/kg and 0.002～0.006 mg/kg, respectively. The recoveries in the blank spiked diet samples were in the range of 70.3%～104.2%, with the RSD in the range of 2.2%～14.2%. The method is simple, accurate and rugged for the determination of fatty acid esters of chloropropanols in diet samples.Fourth, pharmacokinetics studies of 2-MCPD dipalmitate were performed by using the miniature pig. Samples of blood, bile, urine, and tissues including muscle, heart, liver, kidney, spleen, lung, fat, intestines and its contents were collected between 1 h and 48 h after 2-MCPD dipalmitate was given to the miniature pig by gavage administration at the dose of 53.2 mg/kg b.w. (equivalent to 2-MCPD mg/kg b.w.). The result indicated that the residual concentrations of 2-MCPD dipalmitate in blood and tissues were far lower than that of the metabolite 2-MCPD. The atrioventricular model analysis of the 2-MCPD average concentration-time residues in miniature pig blood according to the software of Phoenix Winnonlin 6.3 results showed that the peak time (Tmax) of 2-MCPD in the blood was 5.667 h, the peak concentration (Cmax) was 2.299 mg/L, the elimination half-life (t1/2λ) was 3.326 h, the mean residual time (MRT0-∞) was 14.090 h, the apparent volume of distribution (Vd) was 1.964 L/kg, the plasma clearance (Cl) was 0.365 L/h/kg and the area under curve (AUC0-∞) was 36.033 h*mg/L. The peak time and concentration in heart, liver, spleen, lung, kidney, muscle and other tissues were comparable with that of in the blood, which suggested that 2-MCPD dipalmitate may be rapid metabolised into 2-MCPD in the digestive tract, and quickly reached the balance in heart, liver, spleen, lungs and other tissues after absorption into the blood. Compared with the previous reports, there is large metabolism difference between the miniature pig model and the rat model.At last, the residue level of chloropropanols esters was determined in 9 kinds of 180 samples collected from the 5th Chinese TDS. The results showed that 3-MCPD esters and 2-MCPD esters have positive detection in 20 provinces and regions but for the 1,3-DCP esters and 2,3-DCP esters.3-MCPD esters and 2-MCPD esters were detected in TDS samples representing 72.8% and 58.9%, with the pollution levels ND～573.3 μg/kg and ND～226.4 μg/kg, and the average level of 61.6 μg/kg and 18.2 μg/kg, respectively. The estimated average daily intake of 3-MCPD esters of Chinese people was 1.32 μg/kg bw/d, which was 65.8% of PMTDI of 3-MCPD. The total average daily intake of chloropropanols esters was 1.74 μg/kg bw/d, accounting for 86.8% PMTDI of 3-MCPD. The main sources of the exposure was from vegetables (accounting for 59.1% of the total amount of exposure), followed by the meat and grains (accounting for 12.0% and 8.9% of the total amount of exposure, respectively), and the small proportion from the rest of the several kinds food categories.In summary, this study established the detection methods of chloropropanols esters in food, TDS and bioiogical samples, explored the metabolism and transformation of 2-MCPD dipalmitate in miniature pigs, and assessed the dietary exposure risk of chloropropanols ester of Chinese population from the 5th TDS samples. |
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