Schiff’s Reagent (PAS): Don’t let your stain ghost you- if it’s not pink, rethink!
What it Does
Schiff's Reagent reacts with aldehydes to produce a magenta color, highlighting:
- Glycogen
- Neutral mucins
- Basement membranes
- Fungi
Aldehydes: Why do they matter?
Aldehydes are the main targets formed when periodic acid oxidizes specific carbohydrates like glycogen and mucin.
No Aldehydes = no magenta reaction.
How it Works
Periodic Acid --> Creates aldehydes from carbohydrates
Schiff’s Reagent --> Reacts with aldehydes making the magenta reaction
This reaction is what makes the PAS stain useful; it is used to specifically highlight carbohydrates' structures. If either of these steps fails, the stain will be too weak or negative.
Reagent Appearance: Is it okay to use?
- Pale/clear to light pink Schiff’s Reagent = Good performance, great for use
- Pink haze Schiff’s Reagent = Still okay to use
- Darkened Schiff’s Reagent = oxidized - DO NOT USE
No magenta? What does this mean?
- Oxidized reagent = replace Schiff’s
- Weak or Missed Periodic Acid Step = change periodic acid and repeat stain
- Over-washing
- Schiff’s likes it hot, use warm water when rinsing
Quality Check
- Store cold once opened, and protect from light
- Keep tightly capped
- A working Schiff’s shows light pink initially, developing into a strong magenta after washing.
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