| Cadmium,chromium and lead are highly toxic heavy metals,which have serious toxic effects on animals and humans,and it will be difficult to eliminate from egg after being contaminated.Meanwhile,Sichuan,Shandong,Hebei(Beijing,Tianjin,Hebei)provinces are not only a large animal husbandry,but also exposed to serious environmental pollution,so the health of livestock and poultry is seriously threatened.At present,there are few reports on the distribution and risk assessment of Cd,Cr and Pb in the egg of these provinces.Moreover,the AAS has low sensitivity and time-consuming properties,and ICP-MS is difficult to universal due to its high cost.HR-CS FAAS and HR-CS GFAAS have the advantages of low cost,high stability and high efficiency,by contrast,the detection limit is different.Therefore,the purpose of this study is to determine the concentration of cadmium,chromium,lead in the egg and each breeding link of three provinces by HR-CS FAAS or HR-CS GFAAS,this is serious important to ensure the safety of egg to human health.Experiment 1:The study on rapid detection of cadmium,chromium and lead in the egg.The aim is to establish a detection method for the simultaneous and rapid determination of Cd,Cr and Pb in the egg by optimizing the storage method of egg(frozen,cold storage,cooked,drying and freeze drying),the pre-treatment(extraction,wet digestion,microwave digestion)and instrument condition(acetylene flow and burner height of HR-CS FAAS;pyrolysis and atomization temperature,matrix modifier of HR-CS GFAAS)in this study.The validity of the method is verified by linearity,detection limit and recovery.The results showed as follows:(1)Different storages condition has no effect on Cd,Cr and Pb contents in the egg(P<0.05).Therefore,the collected egg samples were stored by frozen due to the large number of egg samples.(2)The egg samples were digested by microwave digestion with mixture of nitric acid and hydrofluoric acid(4:1 v/v)was the most rapid and accurate pre-treatment.(3)The optimum instrument conditions of HR-CS FAAS are as follows:the flame type of Cd,Cr and Pb were C2H2-Air;the wavelength of Cd,Cr and Pb were 228.8018,357.8699 and 283.306 nm,respectively;the acetylene flow were 55,100 and 65 L/h,respectively;and the burner height were 7,6 and 7 mm,respectively.(4)The optimum instrument conditions of HR-CS GFAAS are as follows:the pyrolysis temperature of Cd,Cr and Pb were 500,1300 and 500 ? respectively;the atomization temperature were 1300,2400 and 1400 ?,respectively;the matrix modifier of Cd and Pb were Pd(NO3)2;and the matrix modifier of Cr was Mg(NO3)2.(5)Under the optimized conditions of HR-CS FAAS,the linear ranges of Cd,Cr and Pb were 20?100 ng/mL,0.5?5 mg/L and 0.5?5 mg/L;the correlation coefficient(R2)of Cd,Cr and Pb were 0.9976,0.9998 and 0.9989,respectively;the detection limits(LOD)of Cd,Cr and Pb were 0.04,0.49 and 0.86 mg/Kg,respectively;the limit of quantitation(LOQ)for Cd,Cr and Pb were 0.13,1.48,2.59 mg/Kg,respectively;the recovery rate for Cd,Cr and Pb were 92.52%?98.21%,96.62%?05.93%and 98.15%?]04.89%,RSD?3.82%.(6)Under the optimized conditions of HR-CS GFAAS,the linear ranges of Cd,Cr and Pb were 5?40 ng/mL,20?100 ng/mL and 20?100 ng/mL;the correlation coefficient(R2)were 0.9998,0.9984 and 0.9991,respectively;the detection limits(LOD)were 0.61,19.57 and 8.35 ?g/Kg,respectively;the limit of quantitation(LOQ)was 1.83,58.7,and 25.1 ?g/Kg,respectively;and the recovery rate were 90.08%?103.33%.93.12%?101.29%,94.99%?101.63%,RSD?7.48%.(7)Analysis speed:HR-CS FAAS(2 h)>HR-CS GFAAS(2.3 h)>traditional AAS(3 h);detection limit(LOD):HR-CS FAAS<HR-CS GFAAS.Experiment 2:Evaluation and Risk monitoring of Cadmium,Chromium and Lead in the egg.A total of 67 different layer farms in Sichuan,Shandong,Hebei(Beijing,Tianjin,Hebei)provinces were chosen to collected eggs,feeds,deep well water,surface water and soil with 268 replicates per type sample,besides,there are 56 and 40 replicates egg samples from supermarket and market,respectively.Then the content of Cd,Cr and Pb in the egg was determined by HR-CS FAAS to assess the level of heavy metal pollution in three provinces.The results showed as follow:(1)The detection rates of Cd were 72.06%,92.31%,100%,and the Cr and Pb were up to 100%in Sichuan,Shandong and Hebei Province.The average contents of Cd,Cr and Pb in the egg from Sichuan,Shandong and Hebei province were 19.90?g/kg,0.24 mg/kg,98.23 ?g/kg;19.15 ?g/kg,0.35 mg/kg,96.25 ?g/kg;21.22 ?g/Kg,0.42 mg/Kg,71.93 ?g/Kg,respectively.All the egg samples did not exceed the Hygienic standard for fresh eggs(Cd:50 ?g/Kg;Pb:200 ?g/Kg).(2)The overall trend of Cd and Cr contents in the egg samples from different scale farms was large and medium scale<small and medium-small scale farm,and the difference was significant(P<0.05),but the average content of Pb in different scale was not significant different(P>0.05).(3)The average content of Cd and Cr in the egg samples from the supermarkets was significantly lower than that from the markets and farms(P<0.05),and the average content of Pb in the egg samples from the market was significantly higher than that in the farms and supermarkets(P<0.05).(4)The estimated exposure dose(EED)in egg from the highest to lowest was Cr,Pb,and Cd,and the lower RQ value indicated that the pollution of heavy metal was comparative low.At the same time,the distribution of RQ value showed that children are sensitive to heavy metals,which should pay more attention in future.(5)The content of Cd,Cr,Pb in the egg showed a significant positive correlation with the Cd,Cr,Pb content in compound feed of laying hens(P<0.05),therefore,the content of Cd,Cr,Pb in egg mainly comes from the compound feed of laying hens.Followed by the deep well water,soil and surface water around the farm.(6)The average contents of Cd,Cr and Pb in compound feeds of laying hens from Sichuan,Shandong and Hebei(Beijing,Tianjin and Hebei)provinces were 0.24,5.01 and 3.67 mg/kg;0.26,4.19 and 2.61 mg/kg;0.25,5.66 and 3.25 mg/kg,respectively.The contents of Cd,Cr,Pb in the compound feed of laying hens of Shandong and the content of Cd in three provinces did not exceed the Notional Hygienic Standard for Feeds.However,the over-limit rate of Cr and Pb in Sichuan were 9.38%and 17.19%,and those in Heibei were 6.73%and 14.42%,respectively.The average content of Cr and Pb in the compound feed of laying hens in Heibei and Shandong was significantly different(P<0.05).The average content of Cd,Cr,Pb in the compound feed of laying hens from large-scale was lower than those from small-scale farms(P<0.05).In summary,the contents of Cd,Cr and Pb in the egg were determined by HR-CS FAAS is more accurate and rapid than HR-CS GFAAS and traditional AAS.The results showed that the distribution of Cd,Cr and Pb in the egg differs in different region,farm scales and sampling sources.The overall pollution of Cd,Cr,Pb in the egg of above three provinces was light,with lower RQ value.However,the pollution level of Cd,Cr,Pb in the compound feed of laying hens is serious,especially the serious Pb pollution.The contents of Cd,Cr,Pb in the egg mainly comes from the compound feed of laying hens,followed by the soil around the farm,deep wall water and surface water. |
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