Q.The best and latest technique for isolation, purification and separation of organic compounds is:

Concept: Separation Techniques in Organic Chemistry

The question asks for the best and latest technique, which points us toward versatility and modern applicability rather than classical methods.

Classical techniques like crystallisation, distillation, and sublimation work well for specific cases—crystallisation for solids differing in solubility, distillation for liquids with different boiling points, and sublimation for compounds that vaporise without melting. However, each is limited to particular physical properties and often requires relatively pure starting materials or large quantity differences. …

When we need to separate organic compounds, we're essentially trying to exploit differences in their physical or chemical properties. The "best and latest" technique isn't just about being modern—it's about versatility, resolution power, and the ability to handle the most challenging separations that older methods cannot.

Let me walk you through why chromatography stands apart from the classical techniques.

Understanding the Classical Methods

The three traditional techniques each have their place, but also clear limitations:

Crystallisation works by exploiting differences in solubility. You dissolve your impure solid in a hot solvent, then cool it slowly so the desired compound crystallises out while impurities stay dissolved. It's excellent for purifying a single compound from a mixture, but it cannot separate multiple similar compounds efficiently. If two substances have comparable solubilities, crystallisation fails.

Distillation separates liquids based on boiling point differences. Simple distillation works when boiling points differ by at least 25–30 °C; fractional distillation can handle closer boiling points. But it's limited to volatile liquids and struggles with thermally unstable compounds that decompose on heating. It also cannot separate compounds with nearly identical boiling points or non-volatile mixtures.

Sublimation is highly specific—it only works for the small subset of compounds that transition directly from solid to gas without melting (like camphor, iodine, naphthalene). Most organic compounds don't sublime, making this technique extremely limited in scope.

Why Chromatography is Superior

Chromatography operates on a fundamentally different principle: differential migration. A mixture is carried by a mobile phase (liquid or gas) through a stationary phase (solid or liquid-coated solid). Each component interacts differently with the stationary phase—some stick more, some less—so they travel at different rates and separate.

The power of chromatography lies in several factors:

1. Universal applicability: It works for solids, liquids, gases, volatile and non-volatile compounds, thermally stable and unstable substances. No other technique has this range.

2. High resolution: Modern chromatographic techniques (HPLC, GC-MS, TLC) can separate compounds with extraordinarily similar properties—even stereoisomers or compounds differing by a single functional group. …