Help with reagents in RNA purification

[Nice2U]

Dear friends,

this is my first time and ny first post in this forum.
I would appreciate if someone could help me. I need to know what is the role of every reagent used in the classical isothiocyanate–phenol:chloroform extraction protocol used in RNA purification.
Here are the reagents:

4 M guanidine isothiocyanate (GITC)
0.02 M sodium citrate
0.5% sarcosyl
2 M Sodium acetate (pH 4.0)
Chloroform:isoamyl alcohol
Isopropanol
Phenol (equilibrated to pH 5.3–5.7 with 0.1 M succinic acid)
β-Mercaptoethanol (β-ME) (14.4 M)
Glycogen (2 mg/ml)
Diethylpyrocarbonate (DEPC)
DEPC-treated water
75% (v/v) ethanol (prepared using DEPC-treated water)


All the best and thanks a lot to everybody.