What is the Phadebas test?
Phadebas is a presumptive test used in forensic science examinations for the detection of areas of possible saliva staining. The test is designed to react with amylase, a digestive enzyme present in saliva.
How is the Phadebas test carried out?
The test used to identify amylase uses Phadebas®, consisting of starch microspheres with a blue dye cross-linked to the starch. In the presence of amylase the starch is digested, releasing the water soluble dye into solution. The resulting blue colour is read semi-quantitatively using a spectrophotometer.
How does Phadebas paper work?
The principle behind the test is that Phadebas®, consisting of starch microspheres with a blue dye cross-linked to the starch, are immobilised on filter paper sheets. In the presence of amylase the starch is digested, releasing the water soluble dye, which diffuses through the pores of the filter paper.
What is Phadebas paper?
Phadebas Press Test contains pre-coated papers that are capable of localising and identifying saliva on any type of fabric or material. Phadebas Tube Test is used for presumptive testing of suspicious stains. The Tube Test assay is very sensitive and is regularly used as an indicative test of visible stains.
What does the phenolphthalein test tell you?
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.
What is a confirmatory test for blood?
Confirmatory tests for blood include identification of blood cells under a microscope [Shaler, 2002], crystal tests such as the Teichman and Takayama tests [Shaler, 2002; Spalding, 2003], and ultraviolet absorption tests [Gaensslen, 1983].
What type of evidence is saliva?
Saliva can be evidence in a number of crimes. Bite marks, licked adhesives (like envelopes and stamps), eating and drink surfaces, or even expectoration (spitting) can yield important DNA evidence. Saliva stains may be difficult to see, and detection can be tricky.
How do you check for saliva stains?
Methods of detection of dried saliva stains
- Chemicals:- various chemicals and enzymes have been tried to detect dried saliva stains.
- Lasers and ultraviolet light, quartz arch tube and argon ion laser[5,6]
Is there a confirmatory test for saliva?
The presumptive test to detect saliva is the alpha-amylase test also known as the Phadebas Test. For confirmatory tests there has not been as much research done compared to blood and semen.
What are the four types of presumptive tests?
Luminol, leuchomalachite green, phenolphthalein, Hemastix, Hemident, and Bluestar are all used as presumptive tests for blood.
How do you test for phenolphthalein?
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.
Which test is used to determine if a blood sample is human?
Ouchterlony test
How it works: The Ouchterlony test is used to determine if a blood sample is human or animal through the comparison of its reactions to specific antibodies. A sample of the unknown bloodstain is placed in a well in an agar gel. Antibodies from human and animal sources of blood are placed in other wells in the gel.
What do you need to know about the Phadebas Test?
The Phadebas Forensic Press test is used for detecting and identifying hidden saliva stains. Locating saliva stains is a challenging task to perform with light sources as these stains don’t fluoresce very well. A study has shown that as many as 40% of saliva stains on garments go undetected when using alternate light sources.
How is Phadebas used to test for amylase?
Its activity in stains is used as an indicator for the presence of saliva. The test used to identify amylase uses Phadebas®, consisting of starch microspheres with a blue dye cross-linked to the starch. In the presence of amylasethe starch is digested, releasing the water soluble dye into solution.
How do you test for Phadebas in saliva?
1. Place a small piece of the sample material in a 10 x 75 test tube. In a second tube, place an equal-sized piece of known saliva stain as a positive control. In a third tube add no sample (negative control). 2. Add 1.0 ml. H2O and 1/4 Phadebas ®tablet to each tube usi ng forceps, not fingers, to handle the tablets. 3. Vortex to mix thoroughly. 4.
What are the uses of Phadebas honey diastase test?
Three years later, Phadebas Honey Diastase Test was launched resulting in totally eight products in the Phadebas portfolio. Phadebas is used in a wide range of applications from quality control tests for food & beverages to detection of saliva stains in forensic investigation .