Establishment And Application Of Detection Methods For Formaldehyde And Dimethylamine In Seafood

Objectives:To develop a quick and efficient method for the detection of formaldehyde and dimethylamine in marine products by optimizing sample detection conditions;and to determine whether formaldehyde is endogenous or exogenous in marine products by testing the content of formaldehyde and dimethylamine in marine products as well as their ratio,so as to provide scientific basis and powerful technological support for law enforcement departments.Methods:1.Establishment of the detection method for formaldehyde:Formaldehyde standard solution series were derivatized with 2,4-dinitrophenylhydrazine under the acidic condition.With the solution of formaldehyde:water?70:30?,flow rate at 0.5 ml/min,as moving phase.The established method was tested for linearity,accuracy,precision,stability,reproducibility,and the detection limit of the method was determined.2.Establishment of the detection method for dimethylamine:The dimethylamine standard solution series was prepared with 2.0mmol/L methanesulfonic acid as eluent,flow rate 1.0mL/min,conductivity cell detection,conductivity cell temperature 35°C,and instrument volume 25?L.Instrument detection.The established method was tested for linearity,accuracy,precision,stability,reproducibility,and the detection limit of the method was determined.3.Analysis of samples:100 samples purchased from coastal area of Qingdao fishing wharf consisted of the marine products of mollusks and crustaceans.The edible part of these samples was taken.After homogenate,2.0g samples were taken.After derivatization with 2,4-dinitrophenylhydrazine and then purification and extraction of derivative liquid,the content of formaldehyde in the marine products was detected using the precolumn derivatization UPLC method.3.0g samples to be tested were taken,and water was added.After vortex oscillation,TCA solution was added for protein precipitation.After vortex oscillation again,it was extracted with ultrasonic for 15min.After centrifugation and activation,filter liquor was collected at the RP column.After filtration membrane,the content of dimethylamine in the marine products was detected using suppressed ion chromatography,with methanesulfonic acid as leacheate.Finally,the ratio of dimethylamine to formaldehyde was calculated,and whether formaldehyde is endogenous or exogenous was determined.Results:1.With the established method of precolumn derivatization UPLC for determination of formaldehyde,the limit of detection was 0.02 mg/kg,the degree of precision was 0.75%².30%,and the average recovery rate was 89.40%.2.With the established method of suppressed ion chromatography for determination of dimethylamine,the limit of detection was 0.02 mg/kg,the degree of precision was 0.14%⁰.49%,and the average recovery rate was 96.73%.3.The four marine products all contained various levels of endogenous formaldehyde.The medians of formaldehyde content in the four marine products were all 0.25mg/kg,which was much less than their mean.The medians of dimethylamine content in prawn,oratosquilla,octopus and squid were 0.51mg/kg,0.77mg/kg,0.40mg/kg and 0.50mg/kg,respectively,which were also much less than their mean.During continuous and dynamic observation of formaldehyde and dimethylamine for 30 days under the storage condition of-20?,the contents of formaldehyde and dimethylamine both increased rapidly in the first week,then increased slowly,and still had an increasing trend on the 30^th day but tended to be gentle.The ratio of dimethylamine to formaldehyde was close to the theoretical mass ratio of 1.5.Conclusions:1.A quick and efficient method for the detection of formaldehyde in marine products has been established,namely precolumn derivatization UPLC,featured by low detection limit,high sensitivity and good reproducibility,which meets the detection requirements.2.A method for the detection of dimethylamine in marine products has been established,namely suppressed ion chromatography,featured by stability,high recovery rate and simple operation,which meets the detection requirements of both sensitivity and accuracy.3.The content of formaldehyde and dimethylamine in most of marine products keeps within a safe range.Some marine products of mollusks and crustaceans in our city contain a certain amount of endogenous formaldehyde,but most of them are in a low level.4.Through testing,the baseline values of background levels of formaldehyde and dimethylamine in four types of marine product were initially established,providing data support for the development of national standards and risk assessment of formaldehyde in aquatic products.