Chemical Tests / Colorimetry / Chromatography / Pregnancy / Steroid Flashcards
Test for proteins
Biuret solution (containing alkali & copper II sulfate) which react in the presence of peptide bonds
Pos test = colour change from blue to lilac
Starch test
Add orange-brown iodine solution to sample
Positive test = blue black colour will appear
Reducing sugars test
Add Benedict’s solution
Hear in a water Bath
Pos test = colour change blue to brick red
Non reducing sugars test
- Heat sample with HCl to hydrolyse the glycosidic bonds & result in 2 monosaccharides = reducing
- Neutralise solution with NaHCO3
- Carry out the normal reducing tests
(Colour change = presence of non-reducing sugar)
How does colorimetry work
Light passed through the coloured liquid sample
The colorimeter measures how much of the light is absorbed
-> this gives an indication of how much colour / pigment is present in the sample
This indicates the concentration of the substance being measured using a calibration curve
How to calibrate a colorimeter
Colorimeters are zeroed using a ‘blank’ typically distilled water in a cuvette & a red filter before each cuvette is inserted
Rf =
Distance moved by the solute / distance moved by the solvent
What’s the solvent and what’s the solute
What does the Rf value indicate
How far the substance has moved in the mobile phase
Small Rf value -> less soluble & large molecule
Stationary phase vs mobile phase
Stationary = either a TLC plate or chromatography paper
Mobile = solvent for biological molecules that travels
Why use colorimeter
Gives quantitative data, which is not biased/ less affected by human error
How do pregnancy tests work?
- urine poured onto test stick
- mobile monoclonal antibodies (attached to dye) bind to hCG in urine
- specific to hCG (complementary shape)
- form hCG antibody complex, which is mobile & moves down the stick
1st vs 2nd window of pregnancy test
How are anabolic steroids tested for
Urine sample analysed using gas chromatography & mass spec
As anabolic steroids are small molecules, which enter nephrons easily & remain in the blood for many days
