Optimization Of Detection Conditions For Heavy Metal In Tea Based On EDXRF

China is the first country to discover and grow tea.The tea culture has a long history and is profound.The tea industry occupies an important position.However,with the rapid development of industrialization and the increase of environmental pollution,the hygiene and quality safety of tea has also been threatened.Heavy metal pollution is one of the serious problems.Therefore,it is imperative to strengthen the monitoring and testing of tea hygiene,quality and safety.Conventional detection technology has high precision and accuracy,but it takes long time.The operation is complicated,and the instruments are huge.It can not give test results in a short time,and is not suitable to use in first-line supervision and inspection.Therefore,it is especially necessary to establish a fast and convenient method for law enforcement personnel to quickly detect heavy metals in tea in the first line.EDXRF technology is a non-destructive fast detection technology.It has a wide range of applications in geology,minerals,materials and other fields because of its rapid,non-destructive advantages.However,there are relatively few applications in the food currently.Therefore,this experiment intends to establish an EDXRF detection method for heavy metal elements in tea,which provides a new method basis for the detection of heavy metal elements in tea,and also broadens the application range of EDXRF detection technology.First,the jasmine tea samples were selected,crushed and passed through140 mesh,100 mesh,80 mesh,and 40 mesh standard sieves.Under different pressures,they were pressed into sheet samples.The pressed sample is tested at 5 s,30 s,60 s,90 s,120 s,150 s respectively.Counting rate and relative standard deviation were used as detection indexes to evaluate the influence of different parameter preparation conditions on the test results.The optimized conditions are: powder sample of 140 mesh standard sieve,4 g,25 MPa constant pressure 30 s tableting,instrument detection time 90 s.Secondly,therose tea(flower substitute tea),honeysuckle tea(flower substitute tea),chrysanthemum tea(flower substitute tea),Huangshan green tea(traditional tea),Gongfu black tea(traditional tea)are pressed into sheet samples under optimized conditions.Sheet samples and unscreened,uncompressed powder samples were tested separately.The test results show that the detection counting rate of the sheet samples is almost higher than 16000,while the counting rate of traditional tea in the powder sample is about 15000,and the counting rate of substitute tea is even lower,and some even lower than10,000.It is shown that the test results of the sheet samples under the optimized conditions are generally superior to the powder samples.The sample preparation conditions are applicable to all tea samples including traditional tea and substitute tea.Compared with traditional tea,the difference between the tablet sample and the powder sample of the substitute tea is larger,indicating that the sample preparation condition is superior to the substitute tea detection effect.And for all teas including traditional tea and substitute tea,the detection precision and stability are good,and the relative standard deviation is less than 5%,meeting the experimental testing requirements,which shows all teas including traditional tea and alternative teas can be tested by EDXRF.It shows that EDXRF technology can meet the requirements of first-line testing.It can be used for on-site rapid detection of tea samples.