Abstract: The technology relates to a recycling chromatography method. A sampled is injected into a mobile phase flow stream of a liquid chromatography system creating a combined flow stream. The liquid chromatography system includes at least two columns positioned in series, a valve in fluid communication with the at least two columns, and a detection cell positioned between the at least two columns. The combined flow stream is flowed through the at least two columns and chromatographic peaks of the sample are monitored by the detection cell. The detection cell is configured to measure resolution and width of the chromatographic peaks and automatically switch the valve from a first position to a second position when the measured resolution is less than a desired resolution, the measured width is less than a maximum combined peak width, and a switch count is less than a predetermined maximum number of switches.