Effect of spectral resolution, detector linearity and chromatographic resolution on peak purity calculations

Semi-automated peak trapping recycle chromatography instrument for peak purity investigations

A peak trapping recycle chromatography system has been developed and optimized for peak purity assessment of active pharmaceutical ingredients analyzed by high performance liquid chromatography (HPLC). After being analyzed using a reversed phase analytical column, peaks of interest are trapped and are subsequently introduced to a recycle chromatography system. In addition to the increased effective length afforded the recycling system, the small selectivity difference between the analytical and recycling methods help separate potential impurities under the main peak. For more difficult to separate components, the increased efficiency of recycle chromatography provides the necessary resolution. Over 227,000 theoretical plates have been obtained in the recycle dimension for some compounds. The sensitivity of the system fell short of the target (0.1%), but it did show sensitivity (0.5%) comparable to other peak purity techniques commonly used in the pharmaceutical industry. The recovery and repeatability have also been shown to be adequate for peak purity assessment. The system has also been automated using a Visual Basic macro, simplifying the interface allowing it to be used as an open access instrument.