A facile method for sample preparation of ore for quantitative analysis by laser desorption ionization-time of flight mass spectrometry using an internal standard

Abstract

In the present study, we introduce a facile and rapid method of sample preparation for qualitative and quantitative analysis of copper ore by laser desorption ionization-time of flight mass spectrometry (LDI-TOF-MS). The reproducibility of the analyte peak (its intensity) in LDI-TOF-MS is unsuitable for quantitative analysis of solid samples due to the intensity fluctuation of the laser pulse, inhomogeneity of the analyte in the sample, and sample surface roughness. Therefore, it is necessary to use an internal standard for the quantitative study of elements by the LDI-TOF-MS technique. To overcome these difficulties, we introduce a method for sample preparation with homogenous distribution in a circular cross-section of the laser light beam with a diameter of 4 mm. Also, the sample preparation procedure provides for the possibility of adding an internal standard without requiring dissolution of the solid sample (e.g., rocks). The percentage of elements including Fe, Cu, and Cr was successfully determined in copper ore using this procedure. The average relative standard deviation (RSD) for this method is 6.74%, and the relative error for these elements by the standard addition method is less than 7%. The limit of detection (LOD) for Fe, Cu, and Cr is 0.57, 0.77, and 0.15% W/W, respectively. This method can be used for the elemental analysis of every insoluble solid sample by the LDI-TOF-MS technique without the need for other unique equipment.