(MIC) Microspectrophotometer Lesson

Microspectrophotometer

Microspectrophotometer is one of those scientific terms that seems very complicated and excessively long at first glance. When the word is broken down however, it describes the exact nature of the equipment and becomes very easy to understand! Here is the breakdown:

• Micro - Generally regarded as meaning that something is "small"
• Spectro - Band of colors formed by white light being dispersed
• Photo - Scientific term for "light"
• Meter- Object that measures something

Something small + band of colors formed by light being dispersed + light + measuring device= microspectrophotometer!

Essentially, a microspectrophotometer is a piece of equipment designed to analyze the color and some characteristics of very small samples using light through a prism to visualize the spectra of the sample.

To understand more precisely what a microspectrophotometer does and how it applies to Forensic Science, one must understand the physics concepts behind it. Spectra is a continuum of color formed when a beam of white light is dispersed (as by passage through a prism) so that its component wavelengths are arranged in order. A spectra functions similar to a fingerprint in that the pattern made by the wavelengths of light within the sample identify unique elements and colors within a sample. A spectrophotometer is an instrument that measures the amount of light emitted by a particular wavelength when it passes through a medium. A microspectrophotometer is simply a hybrid tool which combines a microscope with a spectrophotometer to analyze, compare, and discriminate colors and spectra within very small samples. For example, when looking at the color "blue", it may be described by a group of five people in five different subjective terms such as "azure", "blue", "cornflower", "cobalt" or "sapphire". This obviously presents a big problem when analyzing evidence based upon color, so how would a forensic scientist be able to objectively state that two samples of paint are the same shade of blue? Microspectrophotometry allows forensic scientists to assign technical markers of color based upon the wavelengths of light found within the sample. If the wavelengths match up in both samples being compared, the scientist could conclude that the colors are a match. This is much more reliable than asking for a color analysis based on the unaided eye assigning a name to a color. This is because the color may be perceived differently in different situations or by different people due to many factors including the light source during the analysis and basic eye anatomy and physiology. A microspectrophotometer also allows the scientist to accurately acquire spectra of extremely small sample areas without changing or damaging the evidence. Measurements can be made while light is transmitted through the sample, reflected from it or even when the sample is made to emit light. It is often used in Forensics for trace evidence analysis such as:

A microspectrophotometer works by emitting a microscopic thin beam of light through a sample toward a photocell sensor mounted on the microscope. The sample absorbs and reflects a small amount of the light, while the rest of the light travels through the sample. The light beam is then measured by the sensor and the reflection, absorption and spectra of the light that traveled through it is calculated. This is how a microscopic paint chip found at a crime scene could be matched to a sample from a suspected car using the microspectrophotometer to identify the spectral fingerprint of both samples.

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