Flow-through radioactivity detection of 3H- and 14C-labelled compounds in reversed-phase liquid chromatography by a liquid scintillation counting technique based on post-column extraction |
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Authors: | AC Veltkamp HA Das RW Frei UATh Brinkman |
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Institution: | Netherlands Energy Research Foundation (ECN), PO Box 1, 1755 ZG Petten The Netherlands;Department of Analytical Chemistry, Free University, De Boelelaan 1083, 1081 HV Amsterdam The Netherlands |
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Abstract: | A method for flow-through liquid scintillation counting in reversed-phase liquid chromatography (RP-LC) based on the continuous extraction of aqueous column eluates with a water-immiscible liquid scintillator is evaluated in terms of sensitivity, reproducibility and extra-column band broadening. 3H- and 14C-labelled phenylthiohydantoinamino acid derivatives of widely different polarity serve as model compounds. For extractable derivatives, counting efficiencies of over 30 and 80% can be obtained for 3H and 14C, respectively. The reproducibility and extra-column band broadening depend on the mixing ratio of scintillator and LC eluent; relative standard deviations (peak areas) of less than 3% can be obtained. The sensitivity of flow-through counting can be increased at least 150-fold by storing the segmented scintillator/eluate stream in a capillary storage loop. After the separation is complete, the stream is re-introduced into the radioactivity detector at reduced flow-rates to increase the mean residence time, i.e., the counting time, in the detector. |
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