Study On EDTA Method For Determination Of Aluminum In Chinese Jellyfish

The content of aluminum in jellyfish products is very high due to the use of alum in salted processing of jellyfish.Thus,the detection and control of alum content in jellyfish is the key to ensure product safety.At present,the titration method is traditionally used for the determination of aluminum content in SC/T 3210-2015 "Salt Jellyfish Skin and Jellyfish Head",however,its accuracy and precision are not ideal,it is imperative to further improve the titration detection method.In this paper,wecollected ready-to-eat jellyfish products from different regions of the china and selected jellyfish products with significant differences in detection results,which were inductively coupled plasma mass spectrometry(ICP-MS).The effects of exogenous additives on the determination of aluminum content were studied.Furthermore,measurement accuracy and precision of EDTA titration were improved by modified pre-treatment digestion technology and titration conditions.The results are as follow:(1)Comparative study on determination methods of aluminum content in jellyfish productsThe difference between ICP-MS spectrometry and EDTA titration in the detection of aluminum of jellyfish products was studied.The results showed the detection limit of ICP-MS spectrometry was 0.34 mg/L,while the detection limit of EDTA titration was 6.8 mg/L.The accuracy and precision of EDTA titration were not satisfactory.The six jellyfish products showed low recovery(69.5-73.1%)and large relative standard deviation(5.3-8.7%).(2)The effect of interference factors on the detection of aluminum residue in jellyfishFour jellyfish products with no significant difference between ICP-MS spectrometry and EDTA titration were selected and the effects of phosphate and organic acids on the results of EDTA titration were investigated.The results showed that the addition of phosphates and organic acids could significantly reduce the recovery of EDTA titration results and increase the relative standard deviation of these jellyfish products.The degree of interference was depended on the number of metal ions and ree hydroxyl groups,which were ionized by and contained in organic acids respectively.The recovery of EDTA detection for jellyfish aluminum content decreased to 72-85%,and the relative standard deviation increased to 2-4%after adding interfering substance.(3)The improvement of EDTA detection for determination of aluminum residue in jellyfishUltrasonic-microwave digestion process and modified titration conditions were used to improve the accuracy and precision of aluminum content detection in jellyfish.The results showed that the recovery of aluminium content in modified EDTA titration was 90.6-93.8%,and the relative standard deviation was 2.5-2.8%when nitric acid,hydrogen peroxide and hydrofluoric acid were selected as digestive agents,ultrasonic power was 500 W,frequency was 20 KHz,digestion time was 1 h,microwave power was 1000W,temperature was 180?,digestion time was 2 h.By further improving the titration conditions,the difference between ICP-MS and EDTA titration was reduced to 5.0-9.6 mg/kg,the recovery was increased to 95.8-96.5%,and the relative standard deviation was reduced to 1.2-1.5%when the concentration of EDTA was 0.06 mol/L,the titration temperature was 80? and the titration pH was 4.5.The accuracy and accuracy of the modified EDTA titration method are basically close to ICP-MS mass spectrometry.