Abstract:
BACKGROUNDSepiolite is a layered hydrous magnesium-rich silicate clay mineral. The content of inorganic elements in sepiolite is an important basis for revealing the source of ore-forming materials, the nature of ore-forming fluids and the genesis of the deposit. It is usually determined by inductively coupled plasma-optical emission spectrometry (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS), high temperature excitation of inductively coupled plasma (ICP) will produce a large number of spectral interferences. High purity argon is needed to maintain the stability of ICP. Continuous gas supply for sepiolite detection in remote mining areas will also cause the problem of inconvenient gas procurement and transportation.
OBJECTIVESIn order to reduce the spectral interference and realize the accurate analysis of major and trace elements in sepiolite samples from remote mining areas.
METHODSAn analytical method was developed for accurate determination of major elements Mg, Al, Ca, Fe, K, Na and trace elements Cu, Zn, Mn and Pb in sepiolite by microwave plasma-atomic emission spectroscopy (MP-AES). Microwave digestion of sepiolite by using HNO3-HCl-HF as a mixed acid not only avoids the loss of analytes during sample processing, but also speeds up the sample processing and improves the stability of the sample solution. By selecting the analysis wavelength of the spectral line for analyte, using the fast linear interference correction (FLIC) technology to correct the spectral interference, and selecting Lu as the internal standard element corrected the matrix effect, which improved sensitivity and accuracy.
RESULTSThe limit of detection (LOD) was 0.19-14.6μg/L. The accuracy of the method was verified by the national standard reference material sepiolite (GBW07138). The relative error between the measured value and the certified value of analytes was between -5.0% and 6.7%, which verified the accuracy and reliability of the method.
CONCLUSIONSThe method has the advantages of low LOD, wide linear range, and accurate results. MP-AES uses its own nitrogen generator to provide nitrogen as the working gas for plasma, without introducing a complex gas, which improves the analysis efficiency, and is especially suitable for remote mining areas where gas procurement and transportation are inconvenient.
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