A recycling chromatography method comprising the steps of: injecting a sample into a mobile phase flow stream of a liquid chromatography system to create a combined flow stream; the liquid chromatography system comprising: a first chromatographic column and a second chromatographic column positioned in series; a valve in fluid communication with the first chromatographic column and the second chromatographic column, the valve having a first operating position and a second operating position; a detection cell in fluid communication with and positioned between the first chromatographic column and the second chromatographic column; and a controller that controls the position of the valve; wherein when the valve is in the first position, the output of the first chromatographic column passes through the valve into the detection cell and the output of the detection cell passes through the valve and into the second chromatographic column; and when the valve is in the second position, the output of the second chromatographic column passes through the valve into the detection cell and the output of the detection cell passes through the valve and into the first chromatographic column, flowing the combined flow stream through the first and second chromatographic columns; and monitoring chromatographic peaks of the sample with a computer coupled to the detection cell, wherein the computer measures resolution and width of the chromatographic peaks and causes the controller to automatically switch the valve from the first position to the second position when the measured resolution is less than a desired resolution, the measured combined peak width is less than a maximum combined peak width, and a switch count is less than a predetermined maximum number of switches. injecting a sample into a mobile phase flow stream of a liquid chromatography system to create a combined flow stream; the liquid chromatography system comprising: a first chromatographic column and a second chromatographic column positioned in series; a valve in fluid communication with the first chromatographic column and the second chromatographic column, the valve having a first operating position and a second operating position; a detection cell in fluid communication with and positioned between the first chromatographic column and the second chromatographic column; and a controller that controls the position of the valve; wherein when the valve is in the first position, the output of the first chromatographic column passes through the valve into the detection cell and the output of the detection cell passes through the valve and into the second chromatographic column; and when the valve is in the second position, the output of the second chromatographic column passes through the valve into the detection cell and the output of the detection cell passes through the valve and into the first chromatographic column, a first chromatographic column and a second chromatographic column positioned in series; a valve in fluid communication with the first chromatographic column and the second chromatographic column, the valve having a first operating position and a second operating position; a detection cell in fluid communication with and positioned between the first chromatographic column and the second chromatographic column; and a controller that controls the position of the valve; wherein when the valve is in the first position, the output of the first chromatographic column passes through the valve into the detection cell and the output of the detection cell passes through the valve and into the second chromatographic column; and when the valve is in the second position, the output of the second chromatographic column passes through the valve into the detection cell and the output of the detection cell passes through the valve and into the first chromatographic column, flowing the combined flow stream through the first and second chromatographic columns; and monitoring chromatographic peaks of the sample with a computer coupled to the detection cell, wherein the computer measures resolution and width of the chromatographic peaks and causes the controller to automatically switch the valve from the first position to the second position when the measured resolution is less than a desired resolution, the measured combined peak width is less than a maximum combined peak width, and a switch count is less than a predetermined maximum number of switches.