Three‐Dimensional Imaging of High Performance Liquid Chromatography Processes Using a Mini Positron Emission Tomograph

Abstract

Positron emission tomography (PET) is a widely used technique for following radiotracer distribution, molecule specific binding or biochemical processes in living animals or in human body. Small animal PET cameras with high spatial resolution and high sensitivity are also useful, beyond their original pre‐clinical application, in the following of surface chemical and the physicochemical processes. The purpose of this study was the introduction of the three‐dimensional real‐time PET based visualization method in separation processes. The separated tracer compounds can be followed and displayed in three dimension along chromatography column using the PET technique. We studied the separation of 11C‐labeled methanol and 11C‐labeled methyl iodide using reversed‐phase high performance liquid chromatography (HPLC) on semi‐preparative and analytical columns in order to determine the detection limits of our PET camera (MiniPET). The PET imaging is suitable for analyzing the column efficiency and the underlying processes in the liquid chromatography. Synthesis, separation and quality control of PET radiopharmaceuticals are performed in radiochemistry labs (in PET Centers) with the help of the liquid chromatography, therefore equipment, infrastructure and other lab conditions are usually available for researchers and for private companies to study chromatographic separation processes and to develop columns.

Compound‐Specific Imaging of Methanol Fuel Cell for Performance and Degradation Studies Using a Mini Positron Emission Tomograph

“…One of them is that the methanol passes only through the anode collector holes purely by diffusion (without pump) and the electrocatalysis processes take place especially just on the expanded down‐stream portions as reactive surface areas (model on Figure 3A). The other of them is that although the catalyst surface size is 20×20 mm, the 11 C‐methanol can pass only through the holes and gas diffusion layer, after that it can only partially spread on the total catalyst surface (Figure 3C) [39–44] …”

“…The other of them is that although the catalyst surface size is 20 × 20 mm, the 11 C-methanol can pass only through the holes and gas diffusion layer, after that it can only partially spread on the total catalyst surface (Figure 3C). [39][40][41][42][43][44] When this new DMFC cell was operated at the first time, the radioactivity concentrations of the hot spots were comparable along the entire anode catalyst surface areas due to the fresh reactive catalyst surface. The somewhat lower radioactive areas around the hot spots (ring-like) confirm that only part of the methanol was able to spray in the gas diffusion layers (Figure 3, 5 A).…”

See the unseen: applications of imaging techniques to study adsorption in microporous materials

“…PET represents an interesting alternative to MRI, because it enables real-time in-situ monitoring of liquid-and gas-phase processes, albeit at a lower spatial resolution (O(l) ∼ mm) [43]. However, because it detects spontaneous decay activity originating from the sample without the need for continuous excitation, PET can be used to investigate separation processes in three-dimensions, while retaining fast acquisition times (∼10 s, Figure 2f) [47]. Moreover, its very high molecule-specific sensitivity enables the study of multicomponent adsorption.…”

“…This is achieved by means of a cylindrical array of detectors, thereby enabling the three-dimensional reconstruction of the adsorptive distribution in the porous medium. Major highlights of PET are the high molecule-specificity (enabling the study of e.g., chromatographic separations[47]), the high-temporal resolution (seconds) and the penetrating power of gamma rays (enabling the monitoring of processes occurring within dense porous materials and inside stainless-steel reactors[43,46]). Positron-emitting isotopes with half-life of a few minutes to a few days are typically used[67], and therefore PET facilities must include a radionuclide generator, or be in proximity of a cyclotron facility.IFM is based on the detection of the phase shift emerging from the superposition of a light beam passing through a porous crystal and another one passing through the surrounding atmosphere[68].…”

“…e. Evolution of the concentration profile of an ethane pulse injected into a 3-cm diameter, 10-cm long column packed with 5A zeolite pellets (helium is the carrier gas flowing at 500 mL/min at room temperature)[60]. f. Radio-chromatographic peaks of 11 C-methyl iodide and 11 C-methanol acquired by PET along the length of a 25 cm-long HPLC column and the corresponding tomograms[47].…”