Spectroscopic Analysis

Image by NASA [Public domain]

Spectroscopy is but one type of analysis I regularly perform. Below is a description of several of the techniques and the information each technique provides.

Spectroscopy involves the measurements of quantities as a function of frequencies or wavelengths, including how energy interacts with matter. These interactions provide information as to the identity and quantity of the composition of the matter.

Energy Dispersive X-ray Spectroscopy (EDS or EDX)

EDS is used to evaluate the elemental composition of materials within a scanning electron microscope (SEM), exciting the sample with X-rays, and then measuring the energy levels of X-rays emitted, which are specific to each element.

Fourier Transform Infrared (FTIR) Spectroscopy

FTIR spectroscopy is a technique in which infrared energy is used to excite fundamental vibrational and associated rotational-vibrational modes of molecules in the mid-infrared, approximately 4000 to 400 cm-1. These vibrational modes correspond to molecular structures. Attenuated Total Reflectance (ATR) is a technique used with FTIR, which allows liquid and solid samples to be studied directly without further preparation. In ATR-FTIR, an infrared beam is directed through an optically dense crystal at a certain angle and internally reflects through the crystal, producing evanescent waves. When the crystal is pressed against an infrared active material, the infrared radiation from the evanescent waves penetrates typically 1 to 4 micrometers into the sample.

Ultraviolet/Visible (UV/Vis) Spectroscopy

UV/Vis is used to measure electronic transitions of molecules in the ultraviolet to visible spectrum, approximately 180 to 800 nm. These transitions correspond to chemical structures which determine to amount of light energy absorbed, transmitted, and reflected, and can be used to characterize certain compounds and optical properties of materials.

X-ray Fluorescence (XRF) Spectrometry

X-Ray Fluorescence (XRF) is used to identify composition and plating thickness for elements ranging from titanium (Ti, element 22) to uranium (U, element 92). By bombarding a sample with high energy X-rays, secondary¬Ě (or fluorescent) X-rays can be emitted which are characteristic of the atoms present in the sample.

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