Microspectrophotometry

Microspectrophotometry (MSP) is a technique used to measure the absorption or transmission spectrum of a solid or liquid material in either transmitted or reflected light.  The method can also be used to measure the emission of light (luminescence, phosphorescence, fluorescence, or cathodoluminescence) from a sample.

In forensic science, MSP is most commonly used to measure and compare the color of single fibers. This can be done using unpolarized light or plain polarized light (to study pleochroism).  Paints, minerals, and a variety of other trace evidence can also be studied.  Using quartz optics, UV absorbing compounds can be characterized and compared through spectral collection down to ~200 nm.  Certain samples which can absorb ultraviolet radiation, can then re-emit these photons in the visible region of the spectrum.  The resulting luminescence (fluorescence or phosphorescence) can then be quantitatively compared using a variety of excitation and barrier filters.

A benefit of the microscope spectrometer is the ability to use apertures which control the analysis area precisely, which permits the quantitative comparison of solid samples.  Liquids can be measured in flat capillaries or studied in our benchtop spectrophotometer with a microcell, which permits the analysis of samples as small as 10 μL in volume.  A near-infrared macro-spectrometer permits the study of molecular overtone and combination bands for a variety of applications ranging from agriculture, to medicine, to materials science.

The five spectrophotometer systems at Microtrace provide a variety of configurations from micro to macro, utilizing tungsten halogen, xenon, deuterium, and mercury illuminators to cover UV through near infrared spectral regions.  These systems can be easily re-configured and adapted for application specific experiments.  Microtrace scientists have conducted a variety of research on microspectrophotometers ranging from the earliest systems through the most current instruments using virtually all detectors and configurations.

Related standardized methods: ASTM E2808

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