What is Kastle-Meyer test used for?
The Kastle-Meyer (KM) test is a quick and easy chemical test for blood used in forensic analyses. Two practical variations of this test are the KM-rub (indirect) test and the more sensitive KM-direct test, the latter of which is performed by applying reagents directly to a suspected blood stain.
What is a Kastle-Meyer reagent?
Kastle–Meyer reagent contains reduced phenolphthalein indicator in a basic solution. For a terrific guided-inquiry forensic activity, use the Kastle–Meyer reagent to investigate substances that will interfere with the test to give false positives.
How does the Kastle-Meyer test work chemically?
The Kastle-Meyer colour test works on a similar principle to Luminol, with an active compound which reacts with hydrogen peroxide in the presence of blood. In this case the chemical involved is phenolphthalein. This will react with hydrogen peroxide in the presence of haemoglobin to produce a pink colour.
How do you make a Kastle-Meyer reagent?
Procedure
- In a test tube, dissolve 0.1 g phenolphthalein in 10.0 ml of 25% sodium hydroxide solution.
- Add 0.1 g mossy zinc to the tube.
- Add a boiling chip and gently boil the solution until it changes color to become colorless or pale yellow.
- Allow the solution to cool.
Is the Kastle-Meyer test 100 accurate?
The test result is actually presumptive positive, meaning it is not a conclusive test for blood, and other analyses would typically be carried out to confirm the presence of blood. Waiting for a period of time over 30 seconds will result in most swabs turning pink naturally as they oxidize on their own in the air.
When should the Kastle-Meyer test be used?
crime scene
The Kastle-Meyer test is a quick inexpensive test used to analyze evidence at a crime scene for the presence of blood. Phenolphthalein reacts with hydrogen peroxide in the presence of hemoglobin to turn from colorless to pink.
What is the positive result of phenolphthalein test for blood?
Phenolphthalein is a presumptive test that reacts with the heme molecule present in blood. A positive reaction gives a pink color.
How accurate is the Kastle-Meyer test?
Using the Kastle‐Meyer technique described, over half of trauma equipment (57%) tested positive for blood, including 15% of equipment that was visibly stained with blood.
How does LMG test work?
The leucomalachite green presumptive test for blood is a catalytic test which is based on the peroxidase-like activity of hemoglobin. Hemoglobin has the ability to cleave oxygen molecules from H2O2 and catalyze the reaction from the reduced form of leucomalachite green to the oxidized blue-green colored product.
Why do you add ethanol to Kastle Meyers test?
If the swab turns pink rapidly, it is said to test presumptive positive for blood. Waiting for periods over 30 seconds will result in most swabs turning pink naturally as they oxidize on their own in the air. The Ethanol component is used to lyse the cells present and gain increased sensitivity and specificity.
Which test can detect blood that has been diluted 300000 times?
The luminol test is capable of detecting bloodstains diluted up to: 300,000 times.