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reagent --> periodic acid Schiff reaction

(Science: technique) A histochemical technique based on periodic acid oxidation of a substance containing the 1,2-glycol grouping.

It is used for staining carbohydrates as the resulting dialdehyde reacts with Schiff reagent to form a coloured product.

The adjacent hydroxyl groups are oxidized to form aldehydes by periodic acid (HIO4) and these aldehyde groups react with Schiff's reagent (basic fuchsin decolourised by sulphurous acid) to give a purple colour.

Acronym: PAS