Development Of Reference Materials Of Dibenzothiophene And Acetanilide For The Content Of Carbon,Hydrogen,Nitrogen And Sulfur

Carbon,hydrogen,nitrogen and sulfur widely exist in coal,petroleum,chemical products,food and soil.Accurate measurement of the content of these elements is of great significance for ensuring product quality,production safety and controlling environmental pollution.The content of these elements is usually measured by infrared absorption method(IR)or thermal conductivity method(TC).These relative measurement methods require the calibration of the reference material(RM)of the pure organic substance for the elemental content.At present,there is no such reference material in China,so it is impossible to achive the traceability.This thesis aims to develop RMs of pure organic substances for the content of carbon,hydrogen,nitrogen and sulfur,calculate the content of target elements according to the content of each component,and focus on the determination of content of organic impurity and trace water.The main contents of the study are shown as follows:The measurement method of the content of impurity in high pure organic substance compounds was studied.Organic impurities were determined by gas chromatography-mass spectrometry(GC-MS),and the limit of detection(LOD)of impurities in solid was 1.0 mg/kg by the selective ion monitoring method(SIM).Differential scanning calorimetry(DSC)was used to determine the content of organic impurities.The accuracy of DSC was improved by using a new calculation of the melted fraction,an introduction of a modification factor of solid solution and a extreme low heating rate.The Karl Fischer method(KF)was used to measure the trace water content of organic substances.The interference of environmental moisture was eliminated through a sampling in a glove box,which endows the method a 5 μg of LOD of mass of water.The regional melting method was adopted to purify the organic substances,by which the content of impurities was reduced to less than 0.01%.The accuracy of element content calculated through the composition is ensured by the ultra-high purity of raw material and the accurate determination of the content of impurities.Based on the above technology,the RM of dibenzothiophene for sulfur and acetanilide for the content of carbon,hydrogen and nitrogen were developed.According to the mass balance method,the purity of dibenzothiophene was 99.9939%.The sulfur content of dibenzothiophene calculated using its compostion is 0.174013 g/g with a relative extended uncertainty is 0.017%.the purity of the acetanilide was 99.9946%.The content and its relavtive extended uncertainty of carbon,hydrogen and nitrogen was 0.71099 g/g(0.009%),0.06712 g/g(0.12%)and 0.10363 g/g(0.07%),respectively,which reaches an international advanced level.The above RMs provide calibration RMs for the measurement of the content of carbon,hydrogen,nitrogen and sulfur in China,which can guarantee the accuracy,reliability and equivalence of the measurement results.Furthermore,the improved DSC method and Karl fischer method have a good potential in the development of RMs of pure organic substances.