Determination of elemental impurities in plastic calibration standards using laser-induced breakdown spectroscopy.

Dual-energy computed tomography (CT) scanning is a rapidly emerging imaging technique employed in nondestructive evaluation of various materials. CT has been used for characterizing rocks and visualizing multiphase flow through rocks for over 25 years. The most common technique for dual-energy CT scanning relies on homogeneous calibration standards to produce the most accurate decoupled data. However, the use of calibration standards with impurities increases the probability of error in the reconstructed data and results in poor rock characterization. Laser-induced breakdown spectroscopy was used to determine impurity concentration in a set of commercially purchased calibration standards used in dual-energy scanning for material identification with coal samples. Two calibration models were developed by using univariate calibration with the internal ratio method and multiple linear regression. Seven elements (Al, Fe, Mg, Na, Ni, Sr, and Ti) were examined in five different samples containing varying amounts of each ion to compare calibration from univariate data analysis and from multivariate data analysis. The contaminant concentrations were also measured by a commercially available inductively coupled plasma optical emission spectroscopy instrument, and the data were used as a reference in developing calibration curves for a modified version of the single linear regression model and the multiple linear regression model.

Application of laser-induced breakdown spectroscopy for total carbon quantification in soil samples.

The increase of greenhouse gas (i.e., CO(2)) levels in the atmosphere has caused noticeable climate change. Many nations are currently looking into methods of permanent underground storage for CO(2) in an attempt to mitigate this problem. The goal of this work is to develop a process for studying the total carbon content in soils before, during, and after CO(2) injection to ensure that no leakage is occurring or to determine how much is leaking if it is occurring and what effect it will have on the ecosystem between the injection formation and the atmosphere. In this study, we quantitatively determine the total carbon concentration in soil using laser-induced breakdown spectroscopy (LIBS). A soil sample from Starkville, Mississippi, USA was mixed with different amounts of carbon powder, which was used as a calibration for additional carbon in soil. Test samples were prepared by adding different but known amounts of carbon powder to a soil sample and then mixing with polyvinyl alcohol binder before being pressed into pellets. LIBS spectra of the test samples were collected and analyzed to obtain optimized conditions for the measurement of total carbon in soil with LIBS. The total carbon content in the samples was also measured by a carbon analyzer, and the data (average of triplicates) were used as a reference in developing calibration curves for a modified version of the single linear regression model and the multiple linear regression model. The calibration data were then used to determine the total carbon concentration of an unknown sample. This work is intended to be used in the initial development of a miniaturized, field-portable LIBS analyzer for CO(2) leak detection.