Study On Determination Of Rare Earth Elements In Plant Foods

REE（Rare Earth Elements） refers to the chemical periodic table lanthanideelements: lanthanum（La）, cerium（Ce）, praseodymium（Pr）, neodymium（Nd）,promethium（Pm）, samarium（Sm）, europium（Eu）, gadolinium（Gd）, terbium（Tb）,dysprosium（Dy）, holmium（Ho）, erbium（Er）, thulium（Tm）, ytterbium（Yb）,lutetium（Lu） and two elements-scandium（Sc） and yttrium（Y） which are closelyrelated to the15elements of the lanthanide elements, a total of17elementscollectively.Rare Earth has environmental accumulation, the bioaccumulation, animalorgans and tissues selective absorption and enrichment, as well as affecting animalgonads and other side effects. The relevant study has demonstrated the rare earth“dose–effect” relationship, namely “Low to promote-high to suppress” of the“stimulus effect”（hormesis）. This stimulatory effect provides a theoretical basis foragricultural using low doses of rear earth to stimulate biological growth. Thisstimulatory effect had provided a theoretical basis for using low-dose rare earth tostimulate biological growth on agriculture. Since the RE can stimulate crop growth,low dose induced growth hormone to stimulate plant growth and development, andthe same human intake RE will also have the effect of similar "stimulus effect",leading to physiological or pathological changes. The study on the biological effectsof China’s southern Jiangxi Rare Earth area has shown that the population of theregion long-term intake of low doses of rare earth through the food chain, leadingchildren’s IQ decreased, adult central nervous conduction blocked, fundusarteriosclerosis increased and certain biochemical abnormalities of the crowd bloodabnormal. Bidirectional considerations from the effect of the "stimulus effect"（hormesis）, rare earth human physiology generated either promote or inhibit theeffect will endanger the health, rare earth’s genetic toxins would harm the futuregenerations. With many years of high-dose using of rare earth fertilizer additive andplant growth regulators, the residual problem of rare earth, in particular, thedetecting problem of residual rare earth which is closely related to people’s lives, has become another major focus of food safety. The content of this paper is incooperation with Jilin Entry-Exit Inspection and Quarantine Bureau, usinginductively coupled plasma mass spectrometry （ICP-MS） testing methods,established a simple, generally applicable, rapid and accurate method for detectingthe15rare earth elements residues in plant-derived foods, and it is also used for thecensus of15rare earth elements in the25provinces in different regions ofplant-derived food.In this paper we have studied the microwave digestion-inductively coupledplasma mass spectrometry detection method of the15rare earth elements in plantfoods. Using microwave digestion as the sample pre-treatment technology, throughexperiments selected HNO₃+H2O₂+HF mixed acid system as microwave digestionsolvent, the addition of HF have solved the problem that rare earth ion is adsorptedby the white silicide precipitate which is produced through the digesting process andthus affect the determination of the rare earth element content; Conducted anoptimization experiment on the amount of the three solvent,the time and thetemperature of the digestion, making the processing method universal applicabilityfor tea samples and other plant-derived samples; The samples after digesting weredetected by inductively coupled plasma mass spectrometry,using Rh and Re as aninternal standard for the correction of the matrix effect and sensitivity drift. Thismethod was used to determine15rare-earth element in the four national standardsubstance green tea （GBW10052）、 the celery （GBW10048） and carrots（GBW10047）, the obtained results were compared with certified values.This research established a reliable basis for Jilin entry-exit inspection andQuarantine Bureau to build a method for determination of rare earth elements inplant foods. The method was used for the detection of the content of rare earthelements in nearly a hundred kinds of plant foods which are collected from25provinces of our country, then carried out a comparative analysis for the rare earthelement content in the different provinces of China plant-derived food. The results ofthe analysis provided a reliable reference for relevant departments to develop varioustypes of plant-derived food REE limited.