In-situ discrimination of gemstones using semi quantitative analysis based on libs-pca method

• Main Author: Mohamad Saufi, Noradilah
• Format: Thesis
• Language: English; English; English
• Published: 2023
• Subjects: QA299.6-433 Analysis
• Online Access: http://eprints.uthm.edu.my/10985/

Laser-induced breakdown spectroscopy (LIBS) is a flexible non-destructive method for qualitative and quantitative analysis. It has its advantages for in-situ elemental analysis applicable to any material. LIBS system was optimized with fundamental 1064nm of Nd:YAG laser and the beam was collimated with plano-convex, convex, and focusing lenses. It aims to identify and classify the elemental differences in the spectrum of gemstones. Gemstone's relative composition was determined using stoichiometric formula. LIBS is performed using 300mJ of Nd:YAG laser and a USB2000+ spectrometer with a spectral range of 600-900nm, which then analyze using the Origin software. The lenses were placed 2cm - 6cm - 11cm respectively from the laser source. The differences in LIBS spectra lines of samples represent the elemental variations in Amethyst, Emerald, and Topaz gemstones. 80% of expected elements such as Si, O, Al, and F were identified. Discrimination in each sample is illustrated with a PCA plot, up to three PCs (principal component) referred to as scree and loadings plot of gemstones. The cluster formed shows that each gemstone has similar characteristics. The overlap cluster may be because they have a similar spectrum but are still distinct in features. LIBS-PCA technique is one of the methods that can be used to highlight spectral differences to identify various gemstones and discriminate real from imitated ones. It could identify, discriminate effectively, and classify gemstones with even minor differences for various samples