March 2007 www.thecolumn.eu.com The Column Dietzel and Grugel Radioactive Chromatography: Determining the Smallest Detectable Peak? Günter Dietzel and Reinhard Grugel, Raytest Isotopenmessgeräte GmbH, Germany. Accurately determining the limit of detection in radioactive chromatography using digital recording is useful for a range of pharmaceutical applications. Radioactivity detection is strongly influenced by the statistical variation of the detected signal of radioactivity. Radioactivity is detected in continuous flow in liquid chromatography (LC) and gas chromatography (GC), or along a trace for thin-layer chromatography (TLC). This results in statistical variations when the interval time of the recording is too small. Small peaks of small radioactive fractions can be hidden in the “grass” of statistical variations. When the statistical variation is reduced by the selection of a long interval time, the baseline may be smooth, but small peaks may be “ironed out” and not discovered. Therefore, the ability to isolate the minimum detectable fraction in a radioactive chromatogram is of paramount importance. Radioactive Chromatography Radioactive chromatography (RC), in terms of separation performance of various fractions, is the same as conventional chromatography. The appropriate LC or GC column or TLC plate is selected for its separation performance for a particular sample mixture. Chromatographic methods such as gradient elution and injection- or spotting-technologies can also be developed to optimize the separation. The peak width at half maximum (FWHM) for the selected column or TLC plate is known and/or can be determined from the Author: Gunter Dietzel and Reinhard Grugel E-mail: guenter.dietzel@raytest.com 15
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Table of Contents for the Digital Edition of The Column - March 2007