Charcoal tubes are best used for which type of molecules?

Charcoal tubes are designed to adsorb gases and volatile organic compounds, particularly those that are nonpolar in nature. Nonpolar molecules have low affinity for polar solvents and tend to be attracted to other nonpolar compounds. The surface characteristics of activated charcoal—its porous structure and hydrophobic nature—make it particularly effective for trapping these types of molecules.

For instance, nonpolar substances such as hydrocarbons, many aromatic compounds, and certain solvents will effectively bind to the surface of charcoal, making it an ideal choice for sampling and analysis of airborne contaminants. This characteristic allows for efficient collection and eventual analysis of nonpolar molecules in various industrial hygiene applications.

In contrast, polar molecules and hydrophilic substances tend to be less effectively captured by charcoal due to the lack of attraction between them and the nonpolar surface of the charcoal. Similarly, inorganic compounds, which can include ions and salts, do not typically interact favorably with charcoal. Thus, the choice of charcoal tubes is specifically aimed at nonpolar molecules.