Detection of Heavy Metals in Environmental Samples Using Laser Spark Analysis

Abstract

Detection of heavy metals in some solid environmental samples has been studied by using time-resolved spectroscopy from a laser spark. The main problems in such application have been explored and several solutions have been suggested and evaluated. It has been found that most of the problems are related to instability of the laser sampling process and of the plasma characteristics. Other problems are related to matrix effects and to spectroscopic interferences. Investigation and optimization of several experimental parameters have been carried out. These include aerosol production, crater formation, size effects and timing effects. In order to solve some of the problems, a special calibration model has been designed. This calibration model is based on Principal Component Regression (PCR) and utilizes many spectral lines of each element. Also, a special renormalization algorithm has been tested for internal calibration. As a result, good calibrations have been obtained with detection limits of ca. 10 ppm. These detection limits are below the current legal requirements for most of the heavy metals in agricultural soils.