Add a drop or two of 70 percent ethanol to the swab. You don’t need to soak the swab. The alcohol does not participate in the reaction, but it does serve to expose hemoglobin in blood so that it can react more fully to increase the sensitivity of the test.
Why is ethanol used in Kastle-Meyer test?
The Ethanol component is used to lyse the cells present and gain increased sensitivity and specificity.
What substances can cause a false positive Kastle-Meyer test result?
The test will give a false positive result when in the presence of vegetable peroxidases, such as those in horseradish, broccoli, cauliflower, etc. Additionally, other oxidizing species in the sample will also cause a false positive.
What are solutions used in the Kastle-Meyer test?
- 0.1 g phenolphthalein powder.
- 25% w/v sodium hydroxide solution (aqueous)
- 0.1 g mossy zinc.
- distilled water.
- 70% ethanol.
What does a positive Kastle-Meyer test result?
Add several drops of Kastle/Meyer reagent. Add several drops of hydrogen peroxide. A positive result will give a bright pink color.
What is Kastle-Meyer reagent?
Classic test for the presence of blood at a crime scene! Kastle–Meyer reagent contains reduced phenolphthalein indicator in a basic solution. Simply wipe a presumptive bloodstain with a cotton swab, add a drop of the reagent, and then apply a drop of hydrogen peroxide.
Why does the Kastle-Meyer test work?
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.
What is the principle of Kastle-Meyer test?
The Kastle-Meyer solution is a phenolphthalein indication solution which has been reduced, usually by reacting it with powdered zinc. The basis of the test is that the peroxidase-like activity of the hemoglobin in blood catalyzes the oxidation of the colorless reduced phenolphthalein into bright pink phenolphthalein.What is Kastle-Meyer made of?
Description: Kastle-Meyer Reagent is 2% phenolphthalein in 20% potassium hydroxide solution; use with hydrogen peroxide for presumptive blood tests.
What does the phenolphthalein test indicate?Phenolphthalein is a presumptive test that reacts with the heme molecule present in blood. A positive reaction gives a pink color. The swab in the image below shows the characteristic color of a positive reaction with the phenolphthalein test, indicating the presence of blood. …
Article first time published onWhat are the advantages and disadvantages of the Kastle-Meyer test?
Advantages – sensitive, definitive test, low false positive test ii. Disadvantages – expensive, time-consuming 3. Testing crime scene samples for blood a. The Kastle-Meyer Test is a presumptive test for blood i.
When was the Kastle-Meyer test?
Answer 2: According to the link below, in asnwer #3, The Kastle-Meyer test was first described in 1903. In 1901, Kastle and Shedd in the U.S. found that biological material could cause the oxidation of phenolphthalin to phenolphthalein in slightly alkaline solutions.
Is the Kastle-Meyer test differentiate between human and canine blood?
By analyzing the results of the sensitivity test, it can be seen that the Kastle-Meyer reagent is capable of detecting human and dog blood up to the dilution of 1: 10,000, while for the cat it was only detectable to be blood up to the dilution of 1: 1,000.
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.
What is the role of hydrogen peroxide in the phenolphthalein test?
This is augmented by testing with presumptive tests for blood, such as the phenolphthalein (Kastle-Meyer) test. … In the presence of hydrogen peroxide, this peroxidase-like activity will catalyze the oxidation of phenolphthalin, which is colorless in solution, into phenolphthalein resulting in a pink colored solution.
What 2 chemicals do scientists use when performing a Kastle-Meyer test?
In the original form, a small amount of the Kastle-Meyer reagent as prepared is mixed with equal volumes of 95% ethanol and 10% hydrogen peroxide solution. The suspect stain is rubbed gently with a small piece of filter paper and a drop of the mixed reagent added to the paper.
Is Kastle Meyer a presumptive test?
Kastle Meyer and Hemastix reagents are presumptive tests commonly used in forensic casework for the detection of blood, and their suitability has been reviewed in numerous publications.
What is the chemical makeup of luminol?
PubChem CID10638Chemical SafetyLaboratory Chemical Safety Summary (LCSS) DatasheetMolecular FormulaC8H7N3O2SynonymsLUMINOL 3-Aminophthalhydrazide 521-31-3 5-amino-2,3-dihydrophthalazine-1,4-dione 5-Amino-2,3-dihydro-1,4-phthalazinedione More…Molecular Weight177.16
What does phenolphthalein test for would this be chemical or physical?
Phenolphthalein is an indicator — a chemical which changes colour depending on whether it meets an acid or a base. It turns purple if it meets something basic, such as ammonia; it stays colourless if it meets an acid like vinegar or a neutral substance like water.
How does luminol detect blood discuss its significance in forensic science?
Forensic investigators use luminol to detect trace amounts of blood at crime scenes, as it reacts with the iron in hemoglobin. … When luminol is sprayed evenly across an area, trace amounts of an activating oxidant make the luminol emit a blue glow that can be seen in a darkened room.
What does the blood clot with from the rabbit in the precipitin test?
Precipitin test—blood is injected into a rabbit; antibodies are formed; the rabbit’s blood is extracted as an antiserum; the antiserum is placed on sample blood. The sample will react with human proteins, if human blood is present.
