Employing Chromatography, one cannot separate-

Chromatography is a physical method of separation that distributes components between a stationary phase and a mobile phase based on subtle differences in molecular properties such as adsorption, partition, and affinity [2]. It is widely used to separate colors from a dye, pigments from natural colors, and drugs from blood samples [3]. While specialized chromatographic techniques can separate isotopes of very light elements like hydrogen due to mass-dependent kinetic effects [4], chromatography generally cannot separate radio-isotopes of the same element. Radio-isotopes possess identical chemical properties and electronic configurations, meaning they interact with stationary and mobile phases in an identical manner. Separation of isotopes typically requires methods based on mass differences, such as mass spectrometry or gas diffusion, rather than the chemical affinity principles that govern standard chromatography. Therefore, radio-isotopes are the least suitable for standard chromatographic separation compared to the other options.

Sources

1. [1] https://pmc.ncbi.nlm.nih.gov/articles/PMC5206469/
2. [2] https://www.sciencedirect.com/topics/materials-science/chromatography
3. [3] https://eprints.gla.ac.uk/221522/7/221522.pdf
4. [4] https://www.science.gov/topicpages/c/chromatographic+separation+method