Application Techniques: Discrimiation of Complex Substances with LIBS

Laser-induced breakdown spectroscopy (LIBS) analysis begins with a focused laser beam that ablates the specimen (sample), generating a small spark. The light, optical emission from the spark, which contains spectral information about the composition of the sample, is collected by an optical system. These spectral data are analyzed for chemical identification.

Although the LIBS spectra comprise mostly atomic emission lines, relative intensities and shapes of these lines depend upon the nature of the sample, and thus, LIBS can discriminate even compositionally similar molecular compounds. Such complex substance identification is achieved using chemometric algorithms to process and compare spectra against a preestablished database.

Chemometric Analysis of Lead in Solder

We used the RT100-B instrument to perform quantitative determination of lead in 12 solder materials. We analyzed several electric solders (obtained as coiled soldering wire), including high-lead solders, low-lead solders, lead-free solders, and silverand antimony-bearing solders. We also analyzed thin solder platings printed on electronic circuit boards (solder leads and solder balls).

We applied a chemometric algorithm known as principal component analysis (PCA) to compare and categorize these spectra, as shown below.

Other Applications

Additionally, PCA and partial least squares (PLS) algorithms were applied to discriminate and identify a variety of complex organic and inorganic samples. Examples include measurement of lead in paint and children’s toys; quality control of fiberglass panels; discrimination of coffee beans from different vendors; identification of generic versus brand-name drugs, analysis of chicken tissues and bones, green herb and tomato leaves and other substances.

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