Leucomalachite Green (LMG)
Definition
The reduced, colourless form of malachite green. It is oxidised to the coloured malachite green form by active oxygen released when haemoglobin catalyses the decomposition of hydrogen peroxide.
- Test type
- Presumptive blood indicator
- Chemical mechanism
- Oxidation by haem peroxidase activity in hemoglobin
- Visual result
- Colorless solution turns green in presence of blood
- Field stability
- More stable in field conditions than Kastle-Meyer test
Common questions
What color change happens in a leucomalachite green test?+
The colorless leucomalachite green solution turns green when blood is present. This color change happens because hemoglobin acts as a catalyst, releasing active oxygen that oxidizes the leucomalachite green to colored malachite green dye.
How sensitive is LMG compared to other blood tests?+
Leucomalachite green is slightly less sensitive than the Kastle-Meyer test, which is another presumptive blood indicator. However, LMG is more stable when used in field conditions, making it practical for on-scene investigation work.
Why is leucomalachite green called a presumptive test?+
It's presumptive because the green color indicates blood may be present, but the test alone cannot confirm blood or identify whose blood it is. A positive result needs follow-up confirmatory testing to be certain.
Related terms
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- Cross-Checking
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- Kastle-Meyer Test
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- Takayama Test
- Confirmatory crystal test. Pyridine, glucose and sodium hydroxide convert haem to pink, feathery pyridine ferroprotoporphyrin (haemochromogen) crystals.
- Teichmann Test
- Confirmatory crystal test. Glacial acetic acid and sodium chloride convert haem to brown, rhombic haemin (ferriprotoporphyrin chloride) crystals. Older, less reliable on...
Explained in these topics
- Detection and Identification of Blood Stains in Forensic SciencePresumptive test where leucomalachite green is oxidised to green malachite green dye by haem peroxidase. Slightly less sensitive than Kastle-Meyer but more sta...
- Leucomalachite Green TestThe reduced, colourless form of malachite green. It is oxidised to the coloured malachite green form by active oxygen released when haemoglobin catalyses the d...