Chromatography software is software that collects and analyzes chromatographic results delivered by chromatography detectors. Predicting and controlling the order of elution is a key aspect of column chromatographic methods. Most analytical techniques involve mass spectrometric detection following gas or liquid chromatographic separation. Changes in enzyme restriction, electrophoretic and chromatographic profiles can be measured. Prior to HPLC scientists used standard liquid chromatographic techniques. Hydrophobic interactions between proteins and the chromatographic matrix can be exploited to purify proteins. This occurs through an insoluble matrix such as chromatographic medium like cellulose or polyacrylamide. The compound is then purified by one chromatographic step followed by crystallization. Thus, isolated yields measured after standard aqueous workup and chromatographic purification should seldom exceed 94%. After ion exchange, generally further chromatographic purification steps and buffer exchange occur. This situation occurs routinely as chromatographic components elute into a continuous ion source. Valio patented the chromatographic separation method to remove lactose. Usually a protein purification protocol contains one or more chromatographic steps. Enantiomeric chromatographic methods are available to distinguish esomeprazole from racemic omeprazole. Combinations of chromatographic methods can be used to purify a target molecule.