Silica Gel vs Aluminium Oxide for Column Chromatography: Which Adsorbent Should You Use for Alkaloid, Antibiotic & Natural Product Purification?
Choosing between silica gel and aluminium oxide isn't a coin flip — it's a decision that determines whether your target compound survives the column or degrades on it. Yet many researchers default to silica gel purely out of habit, even when their compound (alkaloids, antibiotics, basic natural products) would separate far more cleanly on alumina. Here's a manufacturer-level breakdown of when to choose each adsorbent, based on chemistry — not convention. The Core Difference: Acidity, Not Just Particle Size The real distinction between silica gel and aluminium oxide isn't pore size — it's surface chemistry . Silica gel is mildly acidic (pH ~4-5). It performs well for neutral-to-acidic compounds but can cause streaking, tailing, or decomposition of basic compounds like alkaloids. Aluminium oxide is available in acidic, neutral, and basic grades , giving you control over the stationary phase's pH to match your compound...