In a liquid chromatography system, a sample is injected into a column by flowing a solvent mixture from a mixer into the column along a solvent mixture flow path; and injecting a sample into the solvent mixture flow path downstream of the mixer. In another liquid chromatography system, a sample is injected into a column by loading an isolator fluid into a sample loop, loading a sample into the sample loop, and flowing the sample into the column as a plug in front of the isolator fluid.