1. LIMITS OF DETECTION OF AN TOTAL REFLECTION SYSTEM WITH DOUBLE REFLECTION MODULE V. F. Nascimento Filho 1,2, V. H. Poblete 3 P., P. S. Parreira 1,4, E. Matsumoto 5, S. M. Simabuco 5, E. P. Espinoza 1 V., A. A. Navarro 1 1 Laboratório de Instrumentação Nuclear/CENA/USP 2 Departamento de Física e Meteorologia/ESALQ/USP 3 Laboratório de Fluorescencia de Rayos X/CCHEN, Chile 4 Departamento de Física/CCE/UEL 5 Departamento de Recursos Hídricos/FEC/UNICAMP Financial support: FAPESP

2. INTRODUCTION CHARACTERISTICS OF THE TECHNIQUE: •MULTIELEMENTAR, SIMULTÂNEOUS AND INSTRUMENTAL •ATOMIC NUMBER > 13 •HIGH GEOMETRIC EFFICIENCY DETECTION •LOW SAMPLE VOLUMES •MATRIX EFFECT CORRETION NOT NECESSARY •LOW LIMITS OF DETECTION •CAN BE USED FOR : ENVIRONMENTAL MONITORING BIOLOGICAL FLUIDS CONTROL QUALITY OF HIGH PURITY PRODUCTS SOLID SAMPLES (AFTER DIGESTION)

3. Photo and scheme: Total reflection fluorescence system (TXRF): visualization of the tower with the X-ray tube (XRT), high voltage generator (HVG), X-ray detector (XRD) and the total reflection module (TRM).

4. OBJECTIVES •DOUBLE REFLECTOR MODULE ADJUSTMENT •ELEMENTARY SENSITIVITIES DETERMINATION •LIMITS OF DETECTION DETERMINATION

5. MATERIALS and METHODS !X-RAY TUBE: Mo targe, Zr filter, 45 kV/20 mA !TOTAL REFLECTION MODULE: SORAD, Chile !X-RAY DETECTOR: semicondutor Si(Li), 30 mm 2 !PULSE HEIGHT MULTICHANNEL ANALYZER: Canberra !X-RAY SPECTRA FITTING: AXIL !ELEMENTS Cr, Fe, Cu e Zn !STANDARD SOLUTIONS: 2,17 - 8,33 - 15,38 e 31,25 ppm !INTERNAL STANDARD: Y !SAMPLE SUPPORT: quartz !SAMPLE VOLUME ON SUPPORT: 5 microliters !EXCITATION/DETECTION TIME: 500 segundos

7. QUANTITATIVE ANALYSIS C i = concentration of the element i S i = relative sensitivity of the element i R i = relative intensity of the element i I i = intensity of the element i I y = intensity of the internal standard C y = concentration of the internal standard

8. CONCLUSIONS LIMIT OF DETECTION volume of the sample on the support: 50 microliters excitation/detection time: 1000 seconds CHROMIUM IRON COPPER ZINC liquid samples: 18 9 7 6 ppb solid sample: 10 mg digestion; 1 ml final volume 1.8 0.9 0.7 0.6 ppm aerosol filter: 10 m 3 collected volume; digestion; 1 ml final volume 1.8 0.9 0.7 0.6 ng/m 3 Financial support: FAPESP

9. RELATIVE SENSITIVITY

10. LIMITS OF DETECTION

11. REGRESSION LINES