| Objective To optimize a quantitative analysis and detection method for chlorate and perchlorate in milk and dairy products by ultraperformance liquid chromatography-tandem mass spectrometry,to explore the contamination sources of chlorate and perchlorate in sterilized milk,to investigate and analyze the contamination levels of chlorate and perchlorate in commercially available milk and dairy products in Inner Mongolia and to conduct risk assessment.Methods 1.The samples were extracted by different pretreatment methods and purified by Prime HLB solid phase extraction Column.The mobile phase was 20 mmol/L ammonium formate and acetonitrile solution on a Waters Torus TMDEA Column（2.1 mm×100 mm,1.7μm）.Gradient elution was performed.Ultraperformance liquid chromatography-tandem mass spectrometry（UPLC-MS/MS）multi-reaction monitoring mode was used to detect the samples,and internal standard method was used to quantify the samples.2.Analysis of pollution sources of chlorate and perchlorate in sterilized milk selected two dairy enterprises in a city.A total of 145 samples in 11 categories were collected,including environmental samples of forage,drinking water and production water for dairy cows,production process samples of nipple milk,pasteurized milk and finished milk after filling,and disinfection products.The pollution level was obtained by the above detection method,and the key link of pollution was found by comparing the detection rate by chi-square test and comparing the difference of detection values by rank sum test.3.The investigation and analysis of chlorate and perchlorate pollution in commercially available milk and dairy products in Inner Mongolia were carried out by two stage sampling.A total of 524 samples were collected,including 4 categories of liquid milk,including sterilized milk,pasteurized milk,flavored milk and fermented milk,as well as 5 categories of dairy products including milk husk,milk curd,milk strip,milk powder and other unclassified dairy products.The detection values were obtained by the above detection methods,and the chi-square test and rank-sum test were used to compare the differences in the detection rates and detection values of pollutants in sample categories,sampling regions,sampling sites and packaging types,and to describe the pollution levels of chlorate and perchlorate in commercially available milk and dairy products in Inner Mongolia.4.Based on the detection data obtained from the pollution survey and the total dietary consumption data in 2012,simple distribution assessment and cumulative exposure assessment were used to evaluate the exposure levels of chlorate and perchlorate in milk and dairy products of the population in Inner Mongolia.Results 1.In the optimized detection methods,chlorate in the range of 2.0-200.0 ng/m L,perchlorate in the range of 1.0-100.0 ng/m L have a good linear relationship.The limits of detection for chlorate and perchlorate were 1.0μg/kg and 0.3μg/kg,respectively.At low,medium and high supplemental levels,the chlorate recovery ranged from 87.4%to 99.7%,with relative standard deviation（RSD）ranging from 0.6%to 6.1%.The recoveries of perchlorate ranged from 94.3%to 101.0%with RSD ranging from 0.4%to 6.7%.2.Analysis of contamination sources of chlorate and perchlorate in sterilized milk showed that the overall detection rate of chlorate was 19.31%（28/145）,and the detection value was Not Detected（ND）～307.07μg/kg.By chi-square test,the detection rate of chlorate in milk cow nipple bath was significantly higher than other samples（P<0.05）,by Kruskal-Wallis test,the detection value of chlorate in milk cow nipple bath solution was significantly higher than that in water sample and production process sample（P<0.05）;The overall detection rate of perchlorate was95.17%（138/145）,and the detection value ranged from ND to 270.80μg/kg.By chi-square test,the detection rate of perchlorate in forage was significantly higher than that in water samples and milk cow nipple bath liquid（P<0.05）,by Kruskal-Wallis test,the perchlorate detection value of forage was significantly higher than that of other samples except packaging materials（P<0.05）.3.The results showed that the detection rate of chlorate and perchlorate in liquid milk was 23.65%（79/334）,and the detection value ranged from ND to 220.00μg/kg.The chi-square test and rank sum test were used to compare the detection rate and detection value.The results showed that the detection rate and detection value of chlorate in Baotou were both at a high level（P<0.05）,the detection rate was 55.00%（22/40）,the median detection value was 4.38μg/kg,and the interquartile interval was 12.70μg/kg.The detection rate of perchlorate was 75.45%（252/334）,and the detection value ranged from ND to 279.00μg/kg.The detection rate and detection value of perchlorate in Hohhot and Baotou were both at high levels（P<0.05）,the detection rates were 100.00%（34/34）,97.50%（39/40）,the median detection values were 16.15μg/kg,9.41μg/kg,the interquartile spacing was 17.13μg/kg,8.77μg/kg,respectively.The detection rate of chlorate in dairy products was 58.95%（112/190）,and the detection value ranged from ND to 777.98μg/kg.The results showed that the detection rate and detection value of chlorate in milk strip were the highest（P<0.05）,the detection rate was 97.44%（38/39）,the median detection value was 153.02μg/kg,and the interquartile interval was 152.97μg/kg.The detection rate of perchlorate was 98.42%（187/190）,and the detection value ranged from ND to 2748.00μg/kg.The results showed that the perchlorate of milk curd had higher detection value（P<0.05）,the median detection value was 35.21μg/kg,and the interquartile interval was 44.84μg/kg.4.The risk assessment results showed that the daily chlorate exposure of high consumption population in Inner Mongolia was 0.0114μg/kg bw through liquid milk,and the average chlorate exposure through dairy products was 0.0012μg/kg bw,neither exceeded Acceptable daily intake（ADI）or Tolerable daily intake（TDI）.Perchlorate exposure of high consumption population through liquid milk was 0.0148μg/kg bw,and the average chlorate exposure through dairy products was 0.0012μg/kg bw.None exceeded the Provisional Maximum Tolerable Daily Intake（PMTDI）,TDI and Reference Dose（Rf D）.By sex,the high consumption group of females had higher chlorate and perchlorate exposure through liquid milk than males.According to age groups,the high consumption population of 6 to 17 years old had higher chlorate and perchlorate exposure through liquid milk than other age groups.Conclusions 1.The optimized detection method had good separation effect,high sensitivity and accuracy,and was suitable for the detection of chlorate and perchlorate in milk and dairy products.2.Chlorate in the sterilized milk mainly comes from disinfection and cleaning during production and processing,while perchlorate in the sterilized milk mainly comes from forage.3.Chlorate pollution level in commercially available dairy products in Inner Mongolia was relatively high,and perchlorate pollution in milk and dairy products was widespread,which needed to be paid close attention to.4.The dietary exposure risk of chlorate and perchlorate consumed by people in Inner Mongolia through milk and dairy products was low.However,in view of the health hazard of chlorate and perchlorate to the population,it is suggested to formulate the production standard of chlorate and perchlorate in milk and dairy products as soon as possible,and strengthen the production process and source control. |
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