Laser Induced Breakdown Spectroscopy: A Rapid Analytical Technique for Soil and Plant

Abstract

Laser induced breakdown spectroscopy (LIBS) has become one of the most prominent analytical technique with great potential for real time and large-scale soil and plant analyses. In this technology, an intense pulse of laser radiation is focused onto sample where it ablates the material from surface and creates a microplasma. The plasma, excites atoms and atomic ions which emits radiation specific to the elemental composition of the sample and the spectra generated are used for the identification of elements. In a characteristic LIBS spectrum, wavelength corresponds to the type of element and relative strength of spectrum signifies concentration of the element. A well calibrated LIBS instrument performs diverse soil and plant analysis. Its application in detection of soil texture, micro, macro and heavy metals in soil was well documented with high calibration and prediction accuracy. A method for rapid, high resolution (100 μm) and multi-element imaging of root-rhizoshere interface was prepared with LIBS and imaging software to map switch grass (Panicum virgatum) rhizosphere with good limit of detection for soil matrix components and nutrients. LIBS combined with chemometrics was used to detect the cadmium content in rice using extreme learning machine (ELM) model and obtained a prediction accuracy of 93.33 per cent. Laser induced breakdown spectroscopy requires minimal sample preparation for analysis without production of polluting waste and incurs relatively low cost compared to traditional techniques. On the other hand, matrix dependency of measurement, relatively high limit of detection for some elements, unstable signal intensity, and low reproducibility of results due to variations in laser spark are the major limitations.