| China as a major producer of toys and children’s products in the world,quite a number of toys and children’s products are recalled every year because their hazardous substance content is not in conformity with regulations and standards requirements of the exporting countries.Among those hazardous substances,the non-compliance of phthalate esters(PAEs)content in toys and children’s products is the main reason,therefore,much more attentions are paid in detecting PAEs.Meanwhile,in order to provide effective detection technology to toy manufacturers and professional testing laboratories in the face of increasingly heavy testing task of detecting PAEs content in toys and children’s products,the related PAEs testing standard system is urgent to be improved.While the key step in the process of detecting PAEs is the extraction of PAEs,and by choosing a reasonable extraction method,the detection efficiency can be improved and the testing cost can be reduced.Therefore,based on the application of PAEs extraction methods in the available standards,bath-type ultrasonic-assisted extraction method is proposed to extract PAEs from toys and children’s products as well as the standard for determination of PAEs related to the extraction method has been revised accordingly.The main contents of this study are as follows:(1)Establishment of aluminum foil lattice method and characterization of ultrasonic-assisted extraction equipment using aluminum foil lattice method.For the first step,distribution of sound field in ultrasonic equipment was measured by acoustimeter and dyeing method,through which,the influencing factors of cavitation intensity including frequency,preheating time and output power of the ultrasonic equipment as well as the position for the sample located in the equipment were investigated and the optimized operating parameters for extraction have been obtained.Then,the aluminum foil lattice method,which can be used to quantitatively evaluate the cavitation intensity of ultrasonic equipment by calculating the perforated rate of the foil,has been established according to the characteristics of aluminum foil method and the corrosion situation of aluminum foil by ultrasonic cavitation effect under different conditions.The experimental data indicate that the optimal operating parameters of the ultrasonic equipment for acquiring strong cavitation effect are as follows: the ultrasonic frequencies are in the range of 35-45 kHz,and the preheating time and the output power of the instrument are 3 min and 100%,respectively.In addition,the samples are placed in the central area,excluding 25-50 mm horizontally away from the four edges of the tank and 30 or 50 mm vertically away from the bottom of tank.And the evaluation results of the ultrasonic equipment obtained by the aluminum foil lattice method and the actual extraction results of the equipment show that the extraction effect for the target substance such as PAEs can reach more than 80% when the cavitation intensity of the ultrasonic equipment is more than 70% by aluminum foil lattice method.The detailed discussion and results are given in the second chapter of this dissertation.(2)Study on standardization of bath-type ultrasonic-assisted extraction method for PAEs in toys and children’s products.For the first step,the performance of ultrasonic equipment for extracting PAEs in toys and children’s products was characterized by the pre-established aluminum foil lattice method to ensure the equipment meet extraction requirement.For the second step,PAEs in two different types of positive plastic reference samples were extracted by bath-type ultrasonic-assisted extraction method,soxhlet extraction method and solvent extraction method respectively,and then analyzed by GC-MS.The experimental data indicate that the average recovery rates of 6 different types of PAEs extracted by three methods are in the range of 92.1%-105.8%,with relative standard deviations of 2.3%-9.9% and the standard deviations of the average value from 0.1 to 4.5 mg/L.The extraction effect of bath-type ultrasonic-assisted extraction method is consistent well with those of soxhlet extraction method and solvent extraction method in the standard.At the same time,the results of F test and t test show that there are no significant differences in both precision and accuracy between any two of these methods.Therefore,it is reasonable to bring the bath-type ultrasonic-assisted extraction method into the newly revised international standard of PAEs deteciton in toys and children’s products.The detailed discussion and results are given in the third chapter of this dissertation.These research results have not only provided data for the revision of the new international standard ISO 8124-6:2018,in which,proposed a fast,efficient and low cost bath-type ultrasonic-assisted extraction method of extracting PAEs from toys and children’s products for toy manufacturers and professional testing laboratories to improve the testing efficiency and reduce the testing cost,but also established a simple,convenient and inexpensive aluminum foil lattice method to evaluate the performance of daily use of ultrasonic equipment,which can ensure that the instrument meets the extraction requirement and thus the testing result is reliable.We believe this research achievement will promote the development of toy trade for China as well as the whole world. |
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