A SIMPLE METHOD OF DIRECT ANALYSIS FOR THE MULTIELEMENTAL IN BEER USING TOTAL REFLECTION X-RAY FLUORESCENCE

Beer is a drink widely consumed in the world. It is prepared from water, malt, hops and yeast, but other cereals (rice or wheat) can also be used1, 2. This study describes method of direct analysis to quantify 15 inorganic constituents (P, S, Cl, K, Ca, Mn, Fe, Ni, Cu, Zn, Br, As, Rb, Sr and Pb) in beers by total reflection X-ray fluorescence (TXRF) This is a fast and simple multielement technique with wide dynamic range of concentration (µg/L to %). The optimization step evaluated the influence of reading time (100, 250, 500 and 1000 s), internal standard (Ga, Y, Ge) and concentration (1 and 10 mg L-1) using Pilsen beer. This sample was degassed and an aliquot of 50 mL was spiked with contaminants indicated in brazilian legislation3 (200 µg L-1 Pb and 100 µg L-1 As). Samples with and without spiking were analyzed directly by the optimized method. For comparison purposes, beer samples of 5.0 mL were digested with 2.0 mL of HNO3 65% (v/v) and 1.0 mL H2O2 in a microwave oven and analyzed by TXRF using reading time of 500 s and Ga (1.0 mg L-1) as internal standard. The analyte concentrations obtained with and without digestion were not statistically different at 95% confidence. The digestion step generally used for complex matrixes such as beer was not necessary. The recoveries and relative standard deviations (RSD%) found for Pb and As were 103 ± 0.2% and 2% and 107 ± 0.1 % and 1%, respectively. The method was applied to 46 beer samples collected in several regions of the Brazil. The concentration ranges (mg L-1) for the studied analytes were: P: (9.3 - 803); S (0.2 - 278); Cl (34 - 1471); K (84 - 2736); Ca (9 - 362); Mn (0.1 - 13); Fe (0.1 - 12.6); Ni (<LLD - 0.3); Cu (0.02 - 0.6); Zn (0.01 - 1.78); As (0.01 - 0.18); Br (0.14 - 13.14); Rb (<LLD - 2.5); Sr (<LLD - 1.8) and Pb (<LLD - 0.16). Some beer samples presented concentrations of As and Pb above of the limits established by Brazilian legislation3. The developed method is simple, fast, consumes low reagents and allows multielemental determination. TXRF proved to be attractive and useful for routine analysis.