Dynamic Microwave-assisted Leaching Method For The Analysis Of Inorganic Elements In Grain Samples

Microwave-assisted digestion?MAD?has been widely used for the sample pretreatment of food.Compared with traditional sample preparation method,MAD can accelerate the digestion process and decrease reagent consumption and improve automation.Microwave-assisted leaching method has been developed on the basis of flow leaching method,microwave heating replaces traditional heating mode,and microwave energy can provide heat rapidly to promote inorganic elements leaching so that it shortens leaching time.In this paper,based on the dynamic microwave-assisted extraction?DMAE?device in our laboratory,we add peristaltic pump.The new device was used as the microwave-assisted leaching device,and it could control the flow rate availably.The degree of automation of the device is also improved.Based on this new device,we settle several methods of grain sample leaching.We use inductively coupled plasma optical emission spectrometry?ICP-OES?for the detection of the elements in the leaching liquid.The main contents are as follows:1.In this work,a multi-throughput dynamic microwave-assisted leaching method was developed for the leaching of heavy metals?Cu,Cd,Zn,Mn,Ni?in rice,which combined the advantages of microwave digestion technique and dynamic leaching technique.The conditions were optimized in the work: leaching agent;dilute nitric acid?20%,v/v?;the microwave power,300 W,the flow rate of leaching agent,1m L min^-1;the collected volume,10 m L.The leaching agent was diluted,centrifuged and filtration before ICP-OES detection.This method treated six rice samples simultaneously.2.In this work,a multi-throughput dynamic microwave-assisted leaching method was developed for the leaching of trace elements in soybean.Firstly,soybean sample was digested by nitric acid under microwave power of 450 W in 4min,after that,soybean samples were leached with dilute nitric acid?10%,v/v?under microwave power of 450 W,and the collection volume is 10 m L.The precision was between 3.9%⁸.8%.The method was applied to the analysis of several soybean samples with satisfactory result.3.A multi-throughput dynamic microwave-assisted leaching method was developed for the leaching of nutrient elements in oat flakes and nutrient elements in the collected leaching liquid were detected by ICP-OES.The conditions were optimized in the work,first oat flake samples were digested with dilute nitric acid?20%,w/w?under microwave power of 300 W in 2min,then oat flake samples were leached with dilute nitric acid?20%,v/v?under microwave power of 300 W.The flow rate is 1m L min^-1,and the collected volume is 15 m L.The leaching agent was diluted,centrifuged and filtration before ICP-OES detection.Compared with traditional sample preparation method,this method is convenient and efficient and it can treat six oat flake samples simultaneously.