Traceability Method Of Heavy Metal Detector And Development Of Reference Materials

In order to meet the metrological traceability requirement of the rapid detector for heavy metal,the traceability verification of the content of cadmium as the measurement standard was performed,and using reference materials for testing the instrument was proposed.Based on the deficiencies of rice reference materials,standard materials of five concentrations for rice were developed,and they meet the measurement requirements for quality monitoring in the food safety field.In order to meet the verification requirements of the flame atomic absorption spectrometer,series of standard solution of copper in water was independently developed.This paper describes the whole process of the metrology traceability method for rapid detector,and verifies the indicators of the rapid detector from element selection,indication error,repeatability,stability and detection limit.Using standard solution of cadmium and reference material for cadmium in rice,a traceability method for rapid detector was established.Five concentrations of cadmium in rice were selected from the heavy metal contaminated areas in Hunan Province.After the processes of shelling,impurity removal,drying,mixing,comminution,homogeneity,and packaging,five standard substances were obtained and each candidate has 250 bottles.The moisture content of the reserve sample is basically within 5%,and the microwave digestion-graphite furnace atomic absorption determination method for cadmium was optimized.Through the uniformity and stability test,it can be seen that the series of standard samples of cadmium in rice meet the requirements for the development of reference materials.A number of laboratories were used to jointly determine the prepared standard samples and perform an uncertainty assessment analysis.The values of the five standard materials were(7.9±1.5)μg/kg、(0.14±0.02)mg/kg、(1.13±0.16)mg/kg、(2.68± 0.26)mg/kg、(3.44±0.28)mg/kg,respectively.The standard solution of copper in water is often used for the calibration of flame atomic absorption spectrophotometers.Using 2%dilute nitric acid as the solvent,the primary standard material was diluted by gravimetric method to prepare the copper standard solutions of 0μg/mL,0.5 μg/mL,1.0 μg/mL,3.0 μg/mL,5.0 μg/mL.The quantitative analysis of the standard solution was carried out through flame atomic absorption and inductively coupled plasma.The F test and t test proved that the copper standard solution in water has good uniformity and stability.It meets the requirements for the development of secondary standards.The laboratory use two methods to determine the copper standard solution,and the expanded uncertainty was less than 1%.Randomly selected three sets of samples and secondary reference materials(Cu,GBW(E)130079)for concentration comparison,the value of|En| were less than 1,proving that the preparation of the standard solution of the value and uncertainty meet the requirements.