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Application Note HR-CS AAS Flame Technique Determination of Ag, As, Co, Cu, Fe, Mn, Ni, Pb und Zn in Mining Samples Introduction The determination of main and trace elements in samples of the mining industry is of utmost importance. Thus the composition of the extracted ores determines the direction of the further mining process. Chemical additives, required for the subsequent ore treatment need to be analyzed in the scope of process monitoring and the generated slag also is subject to regular inspections. This leads to a high number of samples to be analyzed for a multitude of parameters. Strongly varying element concentrations in a saline sample matrix require a robust analysis technology, which allows a fast, simple and precise determination of a multitude of elements. Therefore High-Resolution Continuum Source Atomic Absorption Spectroscopy (HR-CS AAS) in combination with a flexible autosampler offers an efficient analysis technique. The autosampler enables the fully automatic preparation of calibration standards from a multi-element stock solution and an automatic and intelligent dilution of the samples Individual pre-dilution factors for each sample can be defined in the instrument software. Experimental Samples Ore materials of different composition, provided by GEOSTATS PTY LTD, Australia GBM306-8 Oxide transition copper material GEM 310-15 Copper concentrate GBM398-4 Low grade Cu/Fe/Zn GBM 900-3 Sulfide ore S 5 Internal laboratory standard GBM399-5 Oxide copper ore GBM 398-1 Cu/Pb/Zn cap rock Sample Preparation Approx. 0.1 g of each sample was digested with nitric acid in a microwave digestion system. The solutions then were transferred into a volumetric flask of 25mL and filled to volume with demineralized water. 2/ 11
Determination The determinations were performed using the HR-CS AAS system contraa, equipped with an injection switch SFS 6 and the autosampler AS 52S. For measurement two multi-element methods were applied, which sequentially determine the elements Ag, Fe, Zn and Cu as well as Co, Ni, Mn, Pb and As with an acetylene-air flame. The flame parameters were individually optimized for each element. The strongly differing element concentrations were taken into account by a selection of appropriate analysis lines and an automatic pre-dilution by the autosampler. In case the sample concentration still exceeded the calibrated range, an additional dilution was automatically calculated and executed by the system. Element Programmed predilution factor by autosampler Ag 5 Cu 50 Fe 50 Zn 50 Co 1 Mn 1 Ni 1 Pb 1 As 1 Method Parameters Method1 1: Element Wavelength Flame Fuel Burner- Burner Burner- Type Flow Type angle hight [nm] [L/h] [mm] [ ] [mm] As 193,6960 C 2 H 2 /Air 80 50 0 9 Co 240.7254 C 2 H 2 /Air 50 50 0 6 Mn 279.4817 C 2 H 2 /Air 60 50 0 8 Ni 232.0030 C 2 H 2 /Air 50 50 0 6 Pb 217.0005 C 2 H 2 /Air 55 50 0 5 3/ 11
Method 2: Element Wavelength Flame Type Fuel Flow Burner- Type Burner angle Burnerhight [nm] [L/h] [mm] [ ] [mm] Ag 328,0683 C 2 H 2 /Air 70 50 0 6 Cu 327.3960 C 2 H 2 /Air 50 50 0 6 Fe 302,0639 C 2 H 2 /Air 50 50 0 6 Zn 213,8570 C 2 H 2 /Air 40 50 0 6 Evaluation parameters Method1: Element Integration Time [s] Evaluatio npixel Spectral Observation Width [nm] [Pixel] Background Correction As 3 5 0.23 200 static, with Co 3 5 0.28 200 dynamic, with Mn 3 5 0.32 200 dynamic, with Ni 3 5 0.27 200 dynamic, with Pb 3 5 0.24 200 dynamic, with Method 2: Element Integration Time [s] Evaluation Pixel Spectral Observation Width [nm] [Pixel] Background Correction Ag 3 5 0.40 200 dynamic, with Cu 3 5 0.34 200 dynamic, with Fe 3 5 0.36 200 dynamic, with Zn 3 5 0.23 200 dynamic, with 4/ 11
Calibration: For the determination of As, Co, Mn, Ni and Pb calibration standards of 0.8, 1.4, 2.0, 3.0 and 4 mg/l were automatically prepared by the autosampler from a multi-element solution of 20 mg/l. For the elements Cu, Fe and Zn four standard solutions were prepared of a multi-element stock solution of 100mg/L Fe, 40mg/L Cu and 5mg/L Zn. The calibration standards for Ag were prepared from a single-element stock solution of 10mg/L Ag. For all calibration standards and samples three replicate measurements were performed. As 193.6960 nm Co 240.7254 nm linear; R² = 0.998 nonlinear; R² = 0.9997 Mn 279.4817 nm Ni 232.003 nm nonlinear; R² = 0.9996 nonlinear; R² = 0.9999 5/ 11
Pb 217.0005 nm Zn 213.8570 nm nonlinear; R² = 0.9995 nonlinear; R² = 0.9999 Ag 328.0683 nm Cu 327.3960 nm Fe 302.0639 nm nonlinear; R² = 0.9999 nonlinear; R² = 0.9992 nonlinear; R² = 0.9999 6/ 11
Results Spectra: Ag 328.0683 nm As 193.6960 nm Cu 327.3960 nm Co 240.7254 nm Fe 302.0639 nm Mn 279.4817 nm 7/ 11
Ni 232.003 nm Pb 217.0005 nm Zn 213.8570 nm 8/ 11
Results: Extract of the result table of 20 samples in total Sample GBM306-8* Oxide transition copper material GEM 310-15* Copper concentrate GBM398-4* Low grade Cu/Pb/Zn From surface with laterite GBM 900-3* Sulfide ore Element Automatic Dilution Factor Measured Concentration [mg/kg] RSD [%] Recovery of certified concentration [%] Co - 73 0.1 97 Cu 50 5580 4.0 95 Mn - 552 0.5 - Ni 3.3 1077 0.4 98 Pb - 399 0.7 102 Fe 50 70925 1.5 97 Zn 50 805 1.1 102 As 3.3 1405 0.4 100 Co 10 614 0.9 - Cu 166 218275 ß.5 92 Mn - 295 0.1 - Ni - 272 0.1 93 Pb 4.4 3223 0.5 97 Fe 50 223000 0.4 - Zn 50 11250 0.7 99 Ag - 75 0.2 98 As - 646 2.2 - Co 9.7 1946 0.2 99 Cu 50 36623. 0.6 94 Ni 10 3973 1.8 98 Pb 18.9 11440 0.1 98 Fe 50 46250 1.3 97 Zn 50 5150 1.0 101 Ag - 47 0.5 96 Co - 137 0.7 91 Cu 50 15053 0.1 91 Mn - 458 0.7 - Ni 39.8 32925 0.7 96 Pb - 857 0.4 98 Fe 50 56600 1.4 96 Zn 50 742 1.6 104 Ag - 8.5 0.9 106 9/ 11
Sample Element Automatic Dilution Factor Measured Concentration [mg/kg] RSD [%] Recovery of certified concentration [%] Co 25.6 6450 0.4 96* S 5** GBM399-5* Oxide copper ore GBM 398-1* Cu/Pb/Zn cap rock Cu 50 6175 0.4 95* Mn - 31 0.2 105* Ni 66.7 47835 0.4 97* Fe 125 453000 0.4 91* Ag - 81,5 1.3 101* As 25.4 19575 1.1 107* Co - 45 1.4 95 Cu 50 26325 0.4 89 Mn -- 270 1.2 - Ni 33.6 22803 0.7 93 Pb 33.6 21325 0.5 101 Fe 50 42575 0.9 95 Zn 50 9210 0.2 97 Ag - 24.3 1.0 101 As - 302 1.0 94 Co - 23 1.3 96 Cu 50 14010 0.7 95 Mn 41 18642 2.3 Ni 15.2 9000 1.8 95 Pb 41 26400 0.2 99 Fe 50 34175 2.0 91 Zn 112 19832 1.4 98 Ag - 6.8 2.2 135 *Reference materials from GEOSTATS PTY LTD, 0A Marsh Close, O'Connor, Western Australia 6163 **Values measured by ICP-OES 10/ 11
Discussion The results are in good agreement with the certified values of the materials and with the measurements by ICP OES for sample S-5. The recovery rates for all 20 materials were calculated within a range of 91 to 107 %. For some of the elements, additional absorption lines are visible in the spectrum next to the resonance line of the analyte. These are mainly caused by iron. However, due to the high resolution of the system, no direct line overlay is observed. Hence the measurement is not spectrally interfered. Current versions of the software additionally allow a simultaneous evaluation of several analysis lines in the measurement window. On the Zn absorption line a direct line overlay by a high iron concentration can generally be observed. This can be corrected by a spectral correction, similar to the techniques applied in ICP. In case of the described measurements, however, this direct line overlay could be neglected due to the high sample dilution. Summary High-Resolution Continuum Source AAS is a simple and robust analytical technique for the determination of metals in samples of the mining industry and thus offers an appropriate alternative to classic ICP OES. Thanks to the absorption spectrometric determination with fewer lines, but excellent optical resolution, spectral interferences are minimized and the effort of spectral corrections is significantly reduced. As flame AAS is far less influenced by high matrix contents than ICP OES, for most applications a matrix adaption of the calibration standards is not required. The use of an intelligent autosampler allows the individual predilution of the samples and thus provides a high degree of automation for routine analysis. Chemicals were purchased from Sigma Aldrich. Printout and further use permitted with to the source. 2013 Analytik Jena AG Publisher: Analytik Jena AG Konrad-Zuse-Straße 1 07745 Jena, Germany Phone +49 (0) 36 41 / 77-70 Fax +49 (0) 36 41 77-92 79 www.analytik-jena.com info@analytik-jena.com 11/ 11