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.
What is a 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 solutions are used in the Kastle-Meyer test?
In the Kastle-Meyer test the reduced phenolphthalein is kept in alkaline solution in the presence of zinc. This solution is colourless. Oxidation with haemoglobin and peroxide causes an instant colour change to the well known bright pink. Figure 2 shows the reaction.
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.How do you make a Kastle-Meyer reagent?
- 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.
Why is ethanol used in Kastle-Meyer test?
The Ethanol component is used to lyse the cells present and gain increased sensitivity and specificity.
How is a Kastle-Meyer test performed?
Method. A presumed blood sample is first collected with a swab. A drop of phenolphthalein reagent is added to the sample, and after a few seconds, a drop of hydrogen peroxide is applied to the swab. If the swab turns pink rapidly, it is said to test presumptive positive for blood.
What 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.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 is phenolphthalein used in forensic?Phenolphthalein is a presumptive test that reacts with the heme molecule present in blood. A positive reaction gives a pink color. While bloodstains normally appear red-brown in color, the color of the substrate or the age of a stain may affect the appearance or visibility of the stain.
Article first time published onWhat is luminol and fluorescein used for?
Presumptive reagents, such as luminol and fluorescein, are largely used to detect dilute blood that can not be seen by eye.
What is the use of phenolphthalein?
Phenolphthalein is often used as an indicator in acid–base titrations. For this application, it turns colorless in acidic solutions and pink in basic solutions.
Does luminol only show blood?
The reaction is not specific to blood, however, as other oxidizing agents such as sodium hypoclorite (bleach), certain metals, and plant peroxidases may also cause luminescence with luminol.
What is the Teichmann test?
Teichmann test (haematin test) A confirmatory test for blood based on the formation of distinctive haematin crystals that are viewed under a microscope. The reagents typically used are sodium chloride and glacial acetic acid.
When was the Kastle-Meyer test invented?
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.
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.
Can hydrogen peroxide detect blood?
If hemoglobin is present, the hydrogen peroxide decomposes to yield oxygen that in turn oxidizes the phenolphtalin to phenolphthalein. Since the solution is basic, a pink colour develops indicating the presence of blood. The test is very sensitive, but is not specific for human blood.
What is Victor Meyer test for alcohols?
Victor Meyer’s Test is one of the prominent tests to distinguish between primary, secondary and tertiary alcohol. In this test, the unknown alcohol is subjected to a series of chemical analysis resulting in observation of colour. Different colours are observed for different alcohols.
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.
What is phenolphthalein test chemistry?
The phenolphthalein indicator allows chemists to visually identify whether a substance is an acid or a base. The color change in phenolphthalein is a result of ionization, and this alters the shape of the phenolphthalein molecules.
What types of substances produce false positives with the Kastle-Meyer test for blood?
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 is the role of h2o2 in phenolphthalein 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. The presence of a pink color is a positive test result indicating the presumptive presence of blood.
What is Florence test?
The Florence Iodine test is used to detect the presence of choline, a quaternary saturated amine with the chemical formula (CH3)3N+CH2CH2OH. Choline is an essential nutrient and is found in many foodstuffs, but is particularly concentrated in meat and dairy produce.
What is a luminol test?
Luminol Test. Visitors mix a solution of luminol with fake blood (hydrogen peroxide) to produce a reaction that gives off blue light. OBJECTIVES: Visitors learn that some chemical reactions release energy in the form of light, and that this process is called chemiluminescence.
What does the Takayama test do?
Takayama test is a confirmation test used to detect blood spots. Based on the research results this test can still be used to identify dried blood spots on clothing aged 20 years, and able to detect positively the presence of blood with the formation of pink crystals.
What is the principle involved in the benzidine and phenolphthalein tests?
Principle for phenolphthalein and benzidine test:These test is based on chemical oxidation of a chromogenic substance i.e phenolphthalein / benzidine by an oxidising agent used i.e H2O2. This reaction is catalysed by group of haemoglobin.
Is luminol or fluorescein better?
A presumptive reagent for dilute blood detection other than luminol is fluorescein. The sensitivity of fluorescein approaches the sensitivity of detection levels of luminol. The fluorescein detection method offers the advantages of working in a lighted environment, and the reaction persists longer than luminol.
Does luminol work on old blood?
Luminol can be used to detect bloodstains that are many years old. One disadvantage of using luminol in testing for blood is that it destroys the sample being investigated, making further tests on the same sample impossible.
What is luminol made of?
The “central” chemical in this reaction is luminol (C8H7O3N3), a powdery compound made up of nitrogen, hydrogen, oxygen and carbon. Criminalists mix the luminol powder with a liquid containing hydrogen peroxide (H2O2), a hydroxide (OH-) and other chemicals, and pour the liquid into a spray bottle.
Can you drink phenolphthalein?
Ingestion: Harmful if swallowed. May cause irritation of the digestive tract. Ingestion may cause fever, blood pressure increase and other unspecified vascular effects. Inhalation: May cause respiratory tract irritation.
