Matrix Effects in the Detection of Pb and Ba in Soils Using Laser-Induced Breakdown Spectroscopy

Abstract

With the use of laser-induced breakdown spectroscopy (LIBS), the effects of chemical speciation and matrix composition on Pb and Ba measurements have been investigated by using sand and soil matrices. A cylindrical lens was used to focus the laser pulses on the samples because it yielded higher measurement precision than a spherical lens for the experimental conditions used here. The detection limits for Pb and Ba spiked in a sand matrix were 17 and 76 ppm (w/w), respectively. In spiked soil, the detection limits were 57 and 42 ppm (w/w) for Pb and Ba, respectively. Measurement precision for five replicate measurements was typically 10% RSD or less. Two factors were found to influence emissions from Pb and Ba present in sand and soil matrices as crystalline compounds: (1) compound speciation, where Ba emission intensities varied in the order carbonate > oxide > sulfate > chloride > nitrate, and where Pb emission intensities varied in the order oxide > carbonate > chloride > sulfate > nitrate; and (2) the composition of the bulk sample matrix. Emissions from Ba(II) correlated inversely with the plasma electron density, which in turn was dependent upon the percent sand in a sand/soil mixture. The analytical results obtained here show that a field-screening instrument based on LIBS would be useful for the initial screening of soils contaminated with Pb and Ba.

Burst Mode Q:switched Laser Pulses for Plasma Excitation in LIBS Analysis

“…Quantitative LIBS analysis of specific elements in natural materials is significantly more difficult because of the broad issue known as "matrix effects". This is an observed dependence of the intensity of the LIBS emission response to the nature of the material analysed (Eppler et al, 1996), which manifests as variations in laser-target coupling and resultant plasma intensity variations. These two facets of the sample, which are generally lumped together as "matrix effects" (Aguilera et al, 2009;Corsi et al, 2000;Ctvrtnickova et al;Lu et al, 2010;Ma et al;Mohamed, 2008;Shen et al, 2009;Windom & Hahn, 2009), will determine LIBS signal reproducibility, namely sample composition and sample surface character.…”

Laser-Induced Breakdown Spectroscopy: Fundamentals, Applications, and Challenges

“…Calibration curves can be affected by environmental conditions like changes in the atmosphere around the sample or in the light path [58]. At the same time, uniformity in sample composition, surface roughness, or matrix effects affect the accuracy [59]. All these effects induce the variation of the emission intensity between spectra of the same sample.…”

The Use of Hyphenated Spectrometric Techniques for the Environmental Forensic Assessment of Non-Traditional Pollutants and Degradates in the Greater Florida Everglades

“…These drawbacks, have driven the search for alternative techniques that do not require digestion of the sample and much less sample preparation such as X-ray Fluorescence (XRF) (Goldstein et al, 1996;Kalähne et al, 2006;Buttler et al, 2007), Laser Induced Breakdown Spectroscopy (LIBS) (Eppler et al, 1996), Scanning Electron Microscopy with Energy Dispersive X-ray detector (SEM/EDX) or Wavelength Dispersive X-ray detector SEM/WDX) (Kennedy et al, 2002;dos Anjos et al, 2000;Butler et al, 2006;Butler et al, 2007). Each technique has its own advantages and limitations.…”