| Shellfish poisoning incidents,frequently occurred in recent years and kept threatening seafood safety and people's health.Accurate and sensitive determination methods for multiple shellfish toxins are essential to shellfish toxin monitoring and researches on occurrence and distribution characteristics.In this study,two methods using liquid chromatography-tandem mass spectrometry(LC-MS/MS)combined with solid phase extraction(SPE)pretreatment technique for determination of 9 lipophilic and 13 hydrophilic shellfish toxins were developed and applied to analyzing shellfish samples collected from 5 coastal cities located in the southeast China.Temporal and spatial distribution of shellfish toxins in 5 cities were discussed.The results are as the followings:1.Simultaneous determination method for 9 lipophilic shellfish toxins and DAA simultaneous determination method for DA and 9 lipophilic shellfish toxins(includes OA group,AZAs,YTXs and SPX)was developed.The MS parameters(parent ions,daughter ions,collision energy and gradient elution program)and pretreatment conditions(filter membranes and SPE cartridges,elution solvents and volumes,etc.)were optimized.Matrix effect of target compounds in 3 kinds of matrices(Oyster,Sinonovacula constricta,Turritella bacillum)were observed,therefore,external standard calibration and matrix-matched calibration were used for quantification.More than 90%of recoveries of 10 targets at 3 spiking levels(0.41?169.7 ?g/kg)in 3 kinds of matrices were in the range of 40%?120%with RSD(n=3)within 30%.Method detection limits were in the range of 0.2?20 ?g/kg.Established method was testified accurate and sensitive by the result of 75.7%?110.1%of labeled concentration with RSD(n=3)1.6%-21.7%in the determination of 6 target toxins in certified reference materials.2.Simultaneous determination method for 12 hydrophilic shellfish toxinsSimilarly,a sensitive and accurate method consisted of ultrasonic-assisted extraction,C18+HLB cartridges clean-up and LC-MS/MS detection for 12 hydrophilic shellfish toxins was developed by optimizing instrument and pretreatment conditions.Strong matrix suppression of target compounds were observed in 3 kinds of matrices.Therefore,external standard calibration combined with matrix-matched calibration was used for quantification.More than 80%of recoveries of 12 target compounds at 3 spiking levels(5.08?903.0 ?g/kg)in 3 kinds of matrices were in the range of 60%?110%with RSD(n=3)within 20%.Method detection limits were in the range of 10?50 ?g/kg.3.Monitoring and occurrence and distribution characteristics of shellfish toxins in southeast coast of ChinaThe above developed methods were applied for the determination of 22 shellfish toxins in 243 shellfish samples collected from 5 coastal cites(Xiamen,Putian,Ningde,Taizhou,Wenzhou)in China.Occurrence and distribution characteristics were analyzed as the followings:(1)Occurrence characteristicsThe total detection rates of lipohpilic and hydrophilic shellfish toxins in survey region were 40.7%and 47.3%with detected concentration ND-77.5 ?g/kg and ND-3949 ?g/kg,respectively.AZA2 and dcNEO were most frequently detected and hYTX and DA concentrations were the highest.The positive results showed that snails,clams and oysters were the main species frequently contaminated by shellfish toxins.Except YTXs occurred only in snails,mussels,scallops and few parts of the clams,other target toxins were detected in all 8 kinds of shellfishes.(2)Temporal distribution characteristicsThe total detection rates of lipophilic shellfish toxins showed a tendency of autumn>summer>winter>spring while winter>autumn>summer>spring for hydrophilic shellfish toxins.Higher concentrations of lipophilic and hydrophilic shellfish toxins mainly occurred in autumn and winter seasons.(3)Spatial distribution characteristicsThe highest detection rate of lipophilic shellfish toxins were found in Xiamen while the lowest in Taizhou.The overall detection rates decreased with increasing latitude.Detection rates and concentrations of hydrophilic shellfish toxins showed no significant characteristic.(4)Toxicity evaluationConcentration in all positive samples did not exceed the EU standard limits.Evaluation results showed that most samples contaminated by lipophilic toxins were in low toxicity range,while parts of samples contained hydrophilic shellfish toxins in moderate and high toxicity range. |
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