ICP-MS and AAS as a useful tool in the preparation of reference materials used in the EDXRF techniques

W ramach niniejszej pracy przeprowadzono wnikliwą ocenę technik analitycznych, takich jak: ICP-MS, ASA oraz EDXRF, pod kątem ich przydatności do oznaczania metali ciężkich w próbkach o silnie obciążonej matrycy. Próbki silnie zanieczyszczonych gleb badano za pomocą trzech wyżej wymienionych technik. Pomiar próbek gleb z terenów otaczających byłą Hutę Bobrek za pomocą ICP-MS oraz ASA pozwolił na stworzenie 10 LRM (laboratory reference materials), które następnie zostały dołączone do pozostałych wzorców zastosowanych do klasycznej kalibracji spektrometru EDXRF. Zostało to podyktowane potrzebą rozwinięcia i uzupełnienia posiadanej kalibracji. Przeprowadzono optymalizację mineralizacji gleb, stosując różne mieszaniny roztwarzające oraz dwa różne mineralizatory. Techniki ICP-MS, ASA oraz EDXRF różnią się pod wieloma względami. ICP-MS oraz ASA należą do metod wymagających roztworzenia badanej próbki, natomiast EDXRF nie wymaga przeprowadzenia metali ciężkich do roztworu, tylko pozwala na analizę substancji w stanie stałym. Jedyne co łączy ww. techniki to fakt, że należą one do spektroskopowych metod atomowych (absorpcyjnych ASA, emisyjnych EDXRF czy też wykorzystujących wzbudzenie w plazmie ICP-MS).This study presents the results of a comparison of analytical techniques such as: ICP-MS, AAS and EDXRF in terms of their suitability for the determination of heavy metals in soil samples with complex matrix. Soil samples were tested using three techniques mentioned above. Measurement of soil samples from areas surrounding the former Steelworks "Bobrek" in Bytom, Poland, using ICP-MS and AAS allowed to acquire 10 laboratory reference materials. These LRM were then attached to the other standards used in classical calibration curves used in EDXRF spectrometer. This was dictated by the need to develop a calibration curve used for the analysis of soil samples. Digestion procedure was optimized by using different acid mixtures and two different microwave ovens. It was proved that in the case of soil samples both acidic mixtures, HF/HCl/HNO3 and H2O2/HF/HNO3, can be successfully used for the total digestion. However, when we deal with the extremely contaminated soil sample, then the best solution seems to be complete decomposition using a mixture of H2O2/HF/HNO3. ICPMS, AAS and EDXRF techniques differ in many ways. ICP-MS and AAS are among the methods that require digestion of the sample, while EDXRF allows analysis of the substance in the solid state. The only thing that connects the above techniques is the fact that they belong to atomic spectroscopic methods (absorption AAS, emissions EDXRF or excitation in plasma ICP MS). Comparing the digestion mixture used for the complete digestion, such as HF/HCl/HNO3 and H2O2/HF/HNO3, can be stated that often there is no decisive difference in the results obtained using ICP-MS or AAS analysis in the case of Co, Mn and Cu. There are also cases in which there are significant differences in the obtained results, depending on the digestion procedure, as in the case of As, Cd and Zn. For quantitative analysis of arsenic it should be noted that using ICP-MS technique the main interference in the determination of As is ArCl+ (isobaric interfence). For this reason the best results of the analysis of real samples were obtained during the total digestion using a mixture of H2O2/HF/HNO3. The quantitative analysis allowed to obtain results that are within the following ranges: Cr 60.8 6÷ 240.49 mg/kg; Ba 431.99 ÷ 683.22 mg/kg; Co 7.11 ÷ 23.94 mg/kg; Ni 16,02 ÷ 95.58 mg/kg; Cu 44.21 ÷ 162.00 mg/kg; Zn 764.93 ÷ 3123.13 mg/kg; As 10.17 ÷ 51.54 mg/kg; Cd 3.66 ÷ 9.11 mg/kg; Pb 378.47 ÷ 1165.73 mg/kg; Mn 1050.78 ÷ 6060.71 mg/kg; Fe 7.02 ÷ 32.99 dag/kg. Classification of those soils according to Regulation of the Minister of Environment (dated 9 September 2002) on standards for soil quality and earth quality standards (Journal of Laws No. 165, item. 1359) shows that they are heavily contaminated. In most cases you can qualify those soils for the soil purity class C, but in the case of zinc, lead, manganese and iron concentrations in soils repeatedly exceeded the limits of soils purity