The Microscope - Volume 67, First Quarter 2019
IN THIS ISSUE:
On the cover:
Well-formed, birefringent crystals resulting from a microcrystal test for the drug
l -pseudoephedrine using a dilituric acid reagent; crossed polars. See Microcrystal Tests for the Identification of Illicit Drugs: Phencyclidine, Pseudoephedrine, and Psilocin, page 13.
Editorial | Drug Microcrystal Tests Prove Their Relevance in Criminal Justice, Again
Gary J. Laughlin
The Microscope 67 (1), p ii
Excerpt: This issue of The Microscope journal includes the final installment of original research on microcrystal tests for illicit drugs (see page 13), adapted from McCrone Research Institute’s A Modern Compendium of Microcrystal Tests for Illicit Drugs and Diverted Pharmaceuticals (Microcrystal Compendium). These microcrystal tests, using polarized light microscopy (PLM), can identify most illicit drugs specifically and quickly, usually within a few minutes. They are a reliable check and confirmation of the results and are inexpensive compared to automated instrumental methods.
Since McCrone’s Nov. 25, 2015 publication of the Microcrystal Compendium, available to view or download for free on www.mccroneinstitute.org, these microcrystal tests for drugs have had a measurable and positive impact on the U.S. criminal justice system and achieved their desired result for reliable analytical methods to assist forensic scientists and other researchers in their work.
Calcium Oxalate Phytoliths in Environmental Samples
Russ Crutcher and Heidie Crutcher
The Microscope 67 (1), pp 3 – 11
Abstract: Calcium oxalate phytoliths, most commonly whewellite or calcium oxalate monohydrate (CaC2O4· H2O), are a regular part of environmental samples, though generally at low concentrations. They tend to be misidentified as calcite (CaCO3) in environmental samples due to their very high birefringence (0.160) and similar refractive indices (α = 1.490, β = 1.555, and γ = 1.650). Also, being that typical environmental samples are analyzed in a fixed mounting medium, with no ability to roll the particles individually or change refractive index media easily, leads to their misidentification.
The crystal habits of calcium oxalate phytoliths are unique, which helps differentiate them from environmental calcite. The crystal habit of a phytolith is the result of chemicals in the cells that promote the growth of specific faces. The result is that the habits available to specific plants are under genetic control to some extent. Some of these faces readily form twinned crystals, which also seems to be under some genetic control. These twins add to the diversity of unique crystal habits. They can be grouped into five general habits: laths, styloids, prisms, druses, and sands. Styloids, prisms, and druses are the most diagnostic of the plant from which they originate.
This paper describes the calcium oxalate phytoliths of eight plants: Pseudotsuga menziesii (Douglas fir), Larix occidentalis (western larch), Pinus ponderosa (ponderosa pine), Quercus turbinella (shrub live oak), Rosa nutkana (wild rose), Larrea tridentata (creosote bush), Cercocarpus intricatus (mountain mahogany), and Adenostoma sparsifolium (redshanks). The optical and crystallographic properties of these phytoliths are included with photomicrographs taken with circularly polarized light (CPL) so that all the crystals in the microscope field of view show characteristic interference colors. The setup for CPL and a sodium hypochlorite digestion procedure (wet ashing) for the generation of reference collections are briefly explained in this paper. How calcium oxalate crystals appear in an environmental sample and how to prepare reference materials as needed are also discussed.
Microcrystal Tests for the Identification of Illicit Drugs: Phencyclidine, Pseudoephedrine, and Psilocin
Kelly M. Brinsko, Dean Golemis, Meggan B. King, Gary J. Laughlin, and Sebastian B. Sparenga
The Microscope 67 (1), pp 13 – 30
Abstract: The Microscope is publishing monographs from McCrone Research Institute’s A Modern Compendium of Microcrystal Tests for Illicit Drugs and Diverted Pharmaceuticals, which contains 19 different drugs and their microcrystal test reagents. This issue includes the final installment of monographs, with the following drugs/reagents:
- phencyclidine (PCP)/potassium permanganate
- phencyclidine (PCP)/ammonium thiocyanate
- pseudoephedrine/dilituric acid
- pseudoephedrine/gold chloride
- psilocin/trinitrobenzoic acid
Critical Focus | Come Back Plastic, All is Forgiven
Brian J. Ford
The Microscope 67 (1), pp 31 – 42
Excerpt: People dump plastics into the environment and give them a bad reputation — but we rely on plastics to exist, and our future world will depend on them more than ever.
The Microscope Past: 37 Years Ago | Microcrystal Tests and The “Frye Rule”
Walter C. McCrone
The Microscope 67 (1), pp 43 – 48
Originally published in The Microscope, Vol. 40, Third Quarter, pp 193 – 198, 1992.
Abstract: The Frye rule states that methods used to support a court appearance must be technically sound as recognized generally in the forensic science community. Microcrystal tests have been used for a century but are generally regarded as subjective. This objection can be eliminated by better crystallographic characterization of the resulting precipitates.
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