It is my understanding that the forensic identification of a controlled substance using optical microscopy requires more information that just the classification of the type of crystal formed. Birefrigence, refractive index, angles formed by the crystals, etc are necessary to identify a compound when a reagent produces crystals. Is this a correct If opinion on my part?
If the microscopic test is used for confirmation, is the formation of crystals sufficient or should
additional factors be obtained? Would the instrumental test such as IR, MS or NMR be considered the identification test or confirmatory test when a proper microscopic test performed? If the instrumental test is identification, would the simple formation of a crystal be confirmatory? If the mass spectrum is a poor match with a standard's mass spectrum, what is needed to be observed in the microcrystal test results?
Thank you
Dear Dr. Wayne Morris ,
compound optical microscopy can be used to obtain color, size, crystalline structure, refractive.index, and.other.information.about.water-formed deposits. One of the most powerful tools in optical microscopy is polarized light illumination for particle classification.
Many materials have distinct properties in polarized light—color, brightness, refractive index, and crystalline habits are only a few. These properties can be unique to specific materials and can serve as benchmarks for the experienced microscopist.
The brightness (birefringence) and high refractive index of some compounds, the.characteristic color of some others, and the diffuse fine-particle nature of the clay are distinctive benchmarks that can guide the microscopist in identifying compounds. Transmitted light observation can also be used to do microchemical spot tests to identify cations and anions if one does not have immediate access to a SEM/EDS instrument.
Some disadvantages of.optical microscopy include limited depth of focus, especially in reflected illumination, magnification limitations (∼ 1μm resolution), and lack of direct elemental information. When these limitations are encountered, SEM/EDS techniques is the next logical step in the analytical scheme.
For more info, please see the more estensive and detailed source:
"Mineral Scales in Biological and Industrial Systems" - 1st Edition
By Zahid Amjad
CRC Press (2013)
ISBN 9781466568648
Best regards, Pierluigi Traverso
In the instances I am referring to the standard may not have been run on same mass spectrometer as the unknowns, not close in time to the unknown analysis, or the match looking at relative ratios of fragments to base peak of known sample to that of the unknown samples would be equivalent to Quality of Match of 50-75 out of 100. The question is can either the microcrystal result of shape and color of the crystals and this poor match of MS spectra be considered a scientific identification of the compound in question. I do not think so, as neither result would eliminate all but the reported result. Thank you for your comments above which I think supports my opinion but would like to see your additional thoughts with this additional comment.
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