What is radiochromatography?
Chromatography is a laboratory method performed to separate the different components of a mixture. The mixture is dissolved in a fluid called the mobile phase, which carries it through a structure holding another material, the stationary phase. The various constituents of the mixture travel at different speeds, causing them to separate. There are different types of chromatography; in the case of High-Pressure Liquid Chromatography (HPLC), the mobile phase is a liquid at high pressure (typically 400 bar).
In order to measure the separation of the mixture, its components have to be detectable in some way. There is no universal detector that can monitor all compounds. Thus, different types of HPLC detectors have to be used depending on the properties of the substances to be separated. UV detectors are often used, as many substances typically separated in HPLC absorb light in the UV. Other detectors, measuring diffraction index, light scattering, fluorescence, conductivity, and more, are also used in HPLC. The intensity of the signal measured will be represented in the graph called chromatogram: assuming complete separation, each compound will appear in the chromatogram as a peak. The time of appearance identifies the compound, and the area of the peak quantifies it. In the case of Radio-HPLC (or radiochromatography), the substances to be separated are radioactive, normally because they have been labeled using a radioactive isotope, such as 125I, 14C or 3H. This requires the use of a radioactivity detector in the HPLC system.
Applications of Radio-HPLC
Radio-HPLC has numerous applications in research, diagnostics, quality control, and other fields. Some important applications are:
Pharmaceutical Analysis: Radio-HPLC is a key technology for the separation and quantitation of radiolabeled drugs and putative metabolites in drug development.
Environmental Analysis: A wide variety of contaminants from sources such as industrial waste, landfill sites, pesticides and pharmaceutical drugs can make their way into the environment. The challenging identification of these contaminants demands for highly-sensitive detectors to enable detection of lowest concentrations.
Development and QC of Radiochemicals: Radiochemicals are only as good as the care taken in each preparation step. Strict regulations have to be met during production. Radiochemical purity analysis using Radio HPLC is often required to verify the quality of the produced radiochemicals.
QC of Radiolabeled Antibodies and Proteins: Radiochemical identity and purity analysis of radiolabeled antibodies and proteins using Radio-HPLC is a simple and reliable method to ensure that only the radiolabeled antibody or protein is present in the quality control sample.
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