Study On The Determination Of Multi-elements In Feedstuff By Microwave Plasma Atomic Emission Spectrometry

Potassium(k),calcium(Ca),sodium(Na),magnesium(Mg),phosphorus(P),copper(Cu),iron(Fe),manganese(Mn),cobalt(Co),and molybdenum(Mo)are essential elements for normal physiological functions and metabolism in animals.These elements play an indispensable role during cell growth,reproduction,and immunity,whereas lack of which may lead to clinical pathological characteristics of anorexia,weak disease resistance,and low survival rate.However,excessive intake of some elements also has adverse effects on animals’ health and even results in animal poisoning.Therefore,the dertermination of major and minor elements contents in feedstuff is an important task to control the quality and ensure the safety for feed producers and regulators.So far,methods of elemental analysis mainly contain atomic absorption spectrometry(AAS),atomic fluorescence spectrometry(AFS),inductively coupled plasma atomic emission spectrometry(ICP-AES),inductively coupled plasma mass spectrometry(ICP-MS),which combine with some sample pretreatments,such as dry ashing,acid digestion or microwave digestion or others.In recent years,as a new type of atomic emission spectrometry,microwave plasma emission spectrometer(MP-AES)has comparative advantages: the wide range of dynamic linearity,analysis of high sensitivity,and multi elements analysis.In addition,nitrogen has been used as gas source,which greatly reduces the operation cost.All of those make MP-AES a promising way to replace flame atomic absorption spectrometer.In this paper,the pre-treatment conditions of microwave digestion and MP-AES instrument conditions were optimized for typical feed matrices,and then the analytical method of K,Ca,Na,Mg,P,Cu,Fe,Mn,Zn,Co,and Mo was established by MP-AES to realize the efficient and accurate monitoring multi elements in feedstuff.The main contents of this paper and related results are as follows:1.Optimization of the sample pre-treatment for multi-element in feed.Microwave digestion method was used for the sample pre-treatment,and its heating temperature,holding time,composition of the digestion reagents and preliminary digestion were optimized in this work.The optimum conditions for 0.3-1.0 g feed samples weregradiently heated by microwave digestion(80 ℃ for 5 min,120 ℃ for 5 min,and190℃ for 20 min)followed by the one-night pre-digestion using 6mL HNO3 and 1mL H2O2.2.Establishment of MP-AES method for multi-element analysis in feed.The determination method of K,Ca,Na,Mg,P,Cu,Fe,Mn,Zn,Co,and Mo in feedstuff was established under the optimized conditions of MP-AES.The method limit of quantification(LOQ)for 11 elements were range from 0.13 mg/kg(Mo)~3.37 mg/kg(P).The found concentrations of 11 elements in quality control feed sample(QC-FO-003)were in the range of the certified values,and the spiked recoveries were94.9%(K)~118.4%(Mo).Furthermore,the recommended method was also employed to determine the 11 elements in soybean meal,fish meal,premix,and compound feed,whose results were not significantly different at one day with RSDs <9.9%(n=6),and at different days with RSDs <8.1%(n=4).3.Verification of the recommended method.Five different laboratories were chosen to determine 11 elements in five typical feed samples(soybean meal,fish meal,premix,compound feed,and quality control feed sample)using MP-AES.Through the evaluation equations of Cochran and Grubbs,the microwave digestion MP-AES method performed a good repeatability.