Search results
Results from the WOW.Com Content Network
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.
A dry sample is collected with a swab or filter paper. A few drops of alcohol, then a few drops of phenolphthalein, and finally a few drops of hydrogen peroxide are dripped onto the sample. If the sample contains hemoglobin, it will turn pink immediately upon addition of the peroxide, because of the generation of phenolphthalein. A positive ...
A sterile cotton swab is soaked in distilled water and applied to the area of suspected blood to pick up some of the sample. [5] One drop of alcohol is applied to the swab, followed by the addition of one drop of the phenolphthalein reagent, followed by one drop of hydrogen peroxide. [6] A positive result induces a color change to pink. [4]
For optimal accuracy, the color difference between the two species should be as clear as possible, and the narrower the pH range of the color change the better. In some indicators, such as phenolphthalein, one of the species is colorless, whereas in other indicators, such as methyl red, both species confer a color. While pH indicators work ...
The method of sample acquisition can be refined to avoid unnecessary collection of inhibitors. For example, in forensics, swab-transfer of blood on fabric or saliva on food, may prevent or reduce contamination with inhibitors present in the fabric or food. [3]
Bronchoalveolar lavage specimen stained with Diff-Quik. Diff-Quik is a commercial Romanowsky stain variant used to rapidly stain and differentiate a variety of pathology specimens.
To be produced, the method generally used to synthesize phthalein dyes is effective. This method is used to synthesize phenolphthalein and thymolphthalein. To begin, a 2M equivalent of a phenol or a substituted phenol should be combined with a 1M equivalent of a phthalic anhydride. [1]
The inoculated plates are incubated at 37 °C for 24–48 hours to establish colonies. Fresh bacterial preparations should be used. After colonies have grown on the medium, 2-3 drops of the reagent DMPD are added to the surface of each organism to be tested. A positive test (OX+) will result in a color change violet to purple, within 10–30 ...