Application Of Microwave Digestion-ICP-AES Method In Determination Of Trace Elements In Petrochemical Products

There are a large number of metallic and non-metallic elements in petroleum and its products.At present,more than 40 trace elements are found in petroleum,including alkali metals,alkaline earth metal elements Na,K,Ca,Ba,Mg,transition elements V,Ni,Fe,Cr,Mo,non-metallic elements Cl,Br,Si,P,As and other metal elements Cu,Pb,Ti,Co,Zn,Al,Cd,Cr,Mn,Ag,Sn,and the like.These elements have had an adverse effect on petroleum refining,storage and transportation.Therefore,the establishment of a rapid and accurate method for the determination of metal elements in petroleum and its products is of great significance for the prevention and control of environmental pollution and oil quality monitoring.Inductively coupled plasma torch atomic emission spectrometry?ICP-AES?was used to study the determination of six trace elements in iron,manganese,lead,nickel,copper and aluminum in gasoline and petroleum coke samples.In the experiment,the experimental conditions of the analytical line,RF power,cooling gas flow,atomizing gas flow,peristaltic pump speed,and observation height of the ICP spectrometer were optimized in detail.Under the optimal experimental conditions for determining each element to be tested,the detection limits,precision and linear range of each element were determined.The content of trace elements in gasoline and petroleum coke was determined by ICP-AES spectrometer.The accuracy of the method was verified by spiked recovery test.The recoveries of gasoline samples were between 91.3%and 104.6%,and the recoveries of petroleum coke samples were between 94%and 106%.The results are satisfactory.Gasoline and petroleum coke were digested by microwave digestion,and the conditions for digestion of samples by CEM microwave digestion instrument were investigated.The HNO₃+H₂O₂ system was used to digest the gasoline sample,and the petroleum was coked by dry ashing method,and the ash was subjected to microwave digestion treatment using a nitric acid-hydrofluoric acid-hydrogen peroxide system.The microwave program is set up in three steps.The maximum power of gasoline is 1200W and the temperature is raised to 220°C.The petroleum coke sample has a maximum power of 800 W and is heated to 180°C.The simultaneous determination of various heavy metal elements in the sample can be achieved by ICP-AES.Therefore,the uncertainty of the determination of heavy metal content in gasoline samples by ICP-ES is evaluated by taking iron as an example,and the measurement process is not analyzed.Determine the source of the degree,calculate the synthetic standard uncertainty and the extended uncertainty of the measurement results,and calculate the uncertainty of the weighing process?0.2245%?according to the calculation of each uncertainty.And the constant volume of the test solution?0.153%?introduces less uncertainty,while the measurement repeatability?0.63%?and the sample solution concentration measurement?0.9545%?contribute more to the total uncertainty of Fe content determination which providing a reference method for analyzing oil composition.The results show that the microwave digestion method mainly uses microwave rapid heating and high pressure digestion to increase the heating speed.It has the characteristics of small pollution,high recovery rate,fast digestion rate and complete sample digestion.It has a very significant effect on difficult to dissolve oil products.Combined with ICP-AES detection technology,it features low interference,low detection limit and wide linear dynamic range.