Compositional Analysis of Chalcopyrite Using Calibration-Free Laser-Induced Breakdown Spectroscopy

Abstract

This article presents elemental analysis of an economically important mineral (chalcopyrite) of local origin. Calibration-free laser-induced breakdown spectroscopy (CF-LIBS) methodology based on the assumption of optically thin plasma and local thermodynamic equilibrium was employed for quantitative analysis. Plasma on the surface of the chalcopyrite target was generated by an Nd:YAG laser beam of wavelength 532 nm, pulse width 5 ns, and operated at repetition rate of 10 Hz. A LIBS2000+ detection system, comprised of five spectrometers, covering the spectral range from 200–720 nm, was used to record the signal of the optical emission from the chalcopyrite plasma. Recorded optical spectrum revealed the presence of Cu and Fe as the major elements while Ca and Na were recognized as the minor elements in the target sample. Quantitative analysis has shown that the relative concentrations of Cu, Fe, and Ca in the sample under study were 58.9%, 40.2%, and 0.9% by weight respectively. However, Na was not quantified due to the unavailability of suitable spectral lines, required for CF-LIBS analysis. Results obtained by CF-LIBS were validated by X-ray fluorescence (XRF) analysis, which showed the presence of five compositional elements viz. Cu, Fe, Si, Se and Ag with weight percentages of 58.1%, 35.4%, 5.7%, 0.7%, and 0.1% respectively. These results endorse the effectiveness of the CF-LIBS technique for quantitative analysis of major elements, however, its usefulness in case of minor and trace elements needs further improvement.

Detection and Quantification of Precious Elements in Astrophyllite Mineral by Optical Spectroscopy

“…It is evident from Table 5 that the percentage error between the measurements of CF-LIBS and XRF techniques range from almost 8% to 18% for major elements (Ti, W, Fe), whereas for minor and trace elements, relative error increases from 17% to 88%. These results are consistent with many previous studies suggesting that CF-LIBS performs almost equivalently well for quantifying major elements in a multi-elemental material, but its efficiency reduces for minor and trace element quantification [ 25 , 26 , 27 , 28 , 29 , 30 ]. However, the advantage of LIBS over XRF is the detection of lighter elements in multi-elemental complex materials.…”

“…Being free from the matrix effect, CF-LIBS methodology emerges as an effective alternative and gives reasonable and good quantitative results for geological materials of unknown composition. In previous studies, quantitative results obtained with CF-LIBS showed a reasonable agreement with standard analytical techniques [ 26 , 27 , 28 , 29 , 30 ]. There is no need for reference samples and drawing the calibration curves for each element present in the target sample.…”

“…CF-LIBS technique has been successfully employed for compositional analysis of various types of ores and minerals such as quartz, limestone and granite gneiss [ 26 , 27 , 28 ]. Concentration of Cu along with other elements has been successfully measured using CF-LIBS method in copper-rich minerals such as malachite and chalcopyrite [ 29 , 30 ]. For quantitative analysis, CF-LIBS technique has been implemented for the compositional analysis of meteorites and other extra-terrestrial objects [ 31 , 32 ].…”