Determination of Barium in Purple Clay Products for Food Contact by Energy Dispersive X-Ray Fluorescence Spectrometry

The purpose of this paper is to promote the use of additives in purple clay products for food contact in line with national standards. Through instrumental analysis, this paper has established a non-destructive testing method for toxic barium salt added purple clay products, so that the industry can effectively use this technology for purple clay production quality management and material safety assessment. The method is to directly test the samples by energy dispersive X-ray fluorescence spectrometry, establish a set of standard samples with components to complete the function relationship between photon number and content, and carry out a database of comparison and the precision analysis by a large number of purple clay raw ore, mud raw material and purple clay products in various periods. The process is to analyze the consistency of repeated tests under the selected instruments and operating conditions with RSD in 1.75%similar to 4.83%. The relative standard deviations (RSD) of homogeneity of standard samples are 3.10%similar to 5.59%. The relative standard deviations of 10 purple clay samples are 1.23%similar to 12.30%. The test of the specimens with thickness ranging from 1.9 to 14.1 mm shows the change rate between the test value and the real value is -6.94% to 78.44%. The average content of barium in 109 samples of purple clay ore is 0.029 5%. Tests are carried out on three kinds of clay materials without barium carbonate and two kinds of purple clay materials with barium carbonate of about 3 parts per thousand and the results show mud materials with barium carbonate, and the test value of barium is 0.380%similar to 0.398%. In the mud without barium carbonate, the test value of barium is 0.016 2% to 0.046 1%. The barium content of 11 purple clay ware samples from 1979 and later is 0.238 8% to 0.387 7%. The actual analysis data of 1 085 purple clay samples show that barium content in purple clay products increased gradually after 1979. The conclusion is that this method has the characteristics of non-destructive, high efficiency, high speed, high accuracy, good consistency of repeated tests and easy operation, and it is more suitable for the determination of barium carbonate additive in food contact violet purple sand compared with the chemical test method. At the same time, through a large number of experimental data, it is found that the beginning of the artificial addition of barium carbonate was about 1979. Since then, the content of barium element in purple clay products has shown a rising trend, indicating that in the absence of effective measurement methods and technical supervision, the behavior of adding barium carbonate could not be substantially controlled.