Hemident (McPhail’s Reagent) Assay
FORS 420
Introduction: Hemident is a presumptive test that identifies the presences of
blood. This test contains two reagents that are reliable and sensitive. Hemident
Assay could provide results of a sample as small as one part per million. If blood is
present there would be a colorimetric result of a blue/green color. It identifies
mammal blood.
Materials: Fresh Plate
Sharpee
Horse Sample
Rack
Canine Sample
Micropipette
Positive Blood Sample
Left Reagent
Right Reagent
Procedure: Obtain a fresh plate label it with title of the preformed lab, name and
date a corner where it could be read. Place the sample name above the well where
sample is intended to be placed.
Hemident (McPhail’s Reagent) Assay
FORS 420
- Obtain each sample and give a detail description of each sample. Provide
measurements of each sample. Cut no more than 2mm from sample and provide
the measurement of the cut from sample. After cutting a piece from each sample,
place it into the matching labeled sample well.
- After placing each sample into the proper well, pipette 20 µL of the left reagent
into each well first. Pipette 20 µL of the right reagent into each of the well last.
Hemident (McPhail’s Reagent) Assay
- Make note of the color change and how long it takes to produce the color
change.
FORS 420
Hemident (McPhail’s Reagent) Assay
FORS 420
Questions:
1) What color is the leuco-based form of malachite green?
2) The leuco-based form of malachite green can be oxidized by the catalysis of
to produce a
color.
Circle correct answer
3) Reaction of the hemident assay is carried out under acidic/basic conditions.