By Tammie Painter • Updated Mar 24, 2022
cgj0212/iStock/GettyImages
High‑performance liquid chromatography (HPLC) and gas chromatography (GC) are foundational analytical techniques that separate molecules based on their interaction with a stationary phase and a mobile phase. While the core principle—heavier or less polar compounds eluting more slowly—remains identical, the two methods differ markedly in their operational parameters, column design, and sample compatibility.
HPLC employs a liquid mobile phase, typically a blend of organic solvent (e.g., acetonitrile or methanol), ultrapure water, and additives that optimize solubility and compatibility with the analyte. In contrast, GC uses a gaseous mobile phase; common carriers include helium, nitrogen, argon, or hydrogen, chosen based on analyte volatility and detector requirements.
HPLC columns are usually 4–6 inches long metal or glass tubes packed with silica or polymeric stationary phases. GC columns, on the other hand, are coiled capillary tubes whose interior walls are coated with stationary phases tailored to the analysis. These capillaries can extend up to 100 feet, providing high resolution for volatile compounds.
GC is ideal for volatile, thermally stable analytes—small organic molecules, gases, and low‑boiling liquids. Non‑volatile, high‑molecular‑weight, or charged species (e.g., salts, peptides) are better suited to HPLC, which can handle aqueous and ionic matrices without the need for derivatization.
GC columns reside inside an oven; the temperature is precisely programmed to optimize separation, with higher temperatures accelerating elution but risking analyte degradation. HPLC columns are typically maintained at ambient or controlled room temperature, ensuring consistent interaction between mobile phase and stationary phase.
