Modeling of laser-induced breakdown spectroscopic data analysis by an automatic classifier

David D Pokrajac,Yuriy Markushin,Poopalasingam Sivakumar,Mukti Rana,Daniela Milovic,Gary Holness,Noureddine Melikechi,Jinjie Liu

doi:10.1007/s41060-018-00172-y

Abstract

Laser-induced breakdown spectroscopy (LIBS) is a multi-elemental and real-time analytical technique with simultaneous detection of all the elements in any type of sample matrix including solid, liquid, gas, and aerosol. LIBS produces vast amount of data which contains information on elemental composition of the material among others. Classification and discrimination of spectra produced during the LIBS process are crucial to analyze the elements for both qualitative and quantitative analysis. This work reports the design and modeling of optimal classifier for LIBS data classification and discrimination using the apparatus of statistical theory of detection. We analyzed the noise sources associated during the LIBS process and created a linear model of an echelle spectrograph system. We validated our model based on assumptions through statistical analysis of “dark signal” and laser-induced breakdown spectra from the database of National Institute of Science and Technology. The results obtained from our model suggested that the quadratic classifier provides optimal performance if the spectroscopy signal and noise can be considered Gaussian.

Highlights

Laser-induced breakdown spectroscopy (LIBS) is a multielemental and real-time analytical technique with simultaneous detection of all the elements in any type of sample matrix including solid, liquid, gas, and aerosol [1]
The block diagram of an Andor Mechelle 5000 spectrograph system based on the echelle grating [13,14] is shown in Fig. 1a, while Fig. 1b shows the simplified block diagram
In [39] we demonstrated that a simplified version of the optimal classifier discussed in this study is capable of providing high classification accuracies (> 90%) when a sufficiently large number of principal components are utilized to perform multi-class classification of LIBS data of four proteins diluted in phosphate-buffered saline solution

Summary

Introduction

Laser-induced breakdown spectroscopy (LIBS) is a multielemental and real-time analytical technique with simultaneous detection of all the elements in any type of sample matrix including solid, liquid, gas, and aerosol [1]. In LIBS system, a pulsed laser—such as a Q-switched Nd:YAG, is focused onto the surface of the material to eject a tiny fraction of material (picograms to nanograms) from the surface of the object under investigation. By this process, forming shortlived, highly luminous plasma at the surface of the material is formed. Detection and spectral analysis of the optical radiation formed through this process is used to yield information on the elemental composition of the material which includes atomic composition of the compound

Methods

Results

Discussion

Conclusion