SELENIUM DETERMINATION USING HG-MIP OES IN BEEF AND LIVESTOCK FEED

JAVIER SILVA; MARCELO BELLUZZI; FIORELLA IAQUINTA; ANALÍA SUÁREZ; FLORENCIA CORA JOFRE; MARIANELA SAVIO; MARIELA PISTÓN

Mendoza

Simposio; 15th Rio Symposium on Atomic Spectrometry; 2019

Uruguay is one of the main beef exporters and has one of the highest indexes of internal consumption. The production system is based on native pastures, each animal has an estimated area of pastures of 15000 m2. Meat has an important role in human diet providing essential nutrients. Beef is a selenium (Se) source in the diet and this nutrient level depend on the food received by livestock.The Se contents in meat, pastures and forages were determined by means of hydride generation microwave induced plasma atomic emission spectrometry (HG-MIP OES). A common procedure for sample preparation was developed for beef, pastures and forages using microwave assisted digestion with diluted acid (0.5 g of dried sample with 10 mL of HNO3 4.5 mol L-1). After digestion a prereduction step was carried out: 10 mL of the digested sample + 10 mL of HCl 37 % (w/v) were heated during 60 min in a hot plate, after cooling to room temperature, final volume was completed to 10 mL with ultrapure water. Analytical determinations were performed at 196.026 nm on an Agilent 4210 MIP OES spectrometer equipped with a standard torch and a multimode spray chamber for hydride generation (MSIS, Agilent). The reductant for HG was NaBH4 2% (w/v) in NaOH 0.5 % (w/v). MIP OES operating conditions were: 0.55 L min-1 N2 flow rate; 30 rpm pump speed; -70 viewing position; 10 s read time.The main figures of merit were: linear range assayed from 5 to 50 μg L-1, precision sr(%) = 10. Trueness was assessed using certified reference materials (ERM- BB184 Bovine muscle and Embrapa E1001a Brachiaria Brizantha cv) and by spike/recovery assays. Recoveries were all better than 70 %. LOD was 33 μg kg -1 (3.3s) (LOD =1.7 μg L-1 in solution). Selenium levels ranged from 0.10 to 0.45 mg kg-1 (dry basis) for beef and from 0.11 to 0.18 mg kg-1 for the analyzed pastures and forages. These results are relevant to update information for agronomical purposes in our country.The analytical method developed was successfully applied to beef and vegetable samples using a common sample preparation procedure and an economical technique such as MIP OES achieving very low detection limits for Se determination by coupling hydride generation.