Improved QC of radiopharmaceutcials with a dual-mode instrument for combined r-HPLC and r-TLC analysis

Objectives Radiochromatography data form a key part of the QC that is undertaken on radiopharmaceuticals before release. In Europe, there is a demand for using both r-HPLC and r-TLC in order to quantify the radiochemical purity of the sample, which requires a substantial outlay in terms of both equipment cost and the amount of laboratory space. Here, we describe the development and testing of a dual-mode radiochromatography instrument that is capable of performing r-HPLC and r-TLC analyses simultaneously and independently and offers a very small footprint (<0.25 m²) when compared to the use of two separate instruments

Methods In developing the system, particular attention has been paid to detector optimisation for both chromatographic techniques in order to offer flexibility of use with PMT and PiN-diode based detectors. These have been coupled to a range of scintillators to enable complete characterisation for a wide range of gamma energies, whilst maintaining linearity. In addition, methods to optimise the collimation geometry in order to provide the best peak resolution for r-TLC are described (Fig 1). A bespoke control and DAQ package has been developed in parallel to the instrument to link chromatographic and spectral data for PET QC applications and provide compatibility with a PET LIMS.

Results Tests of the system with samples of ¹⁸F-FDG and ¹³⁷Cs calibration standards (662 keV gammas) have confirmed the suitability of the system to perform routine r-HPLC and r-TLC measurements for radiochemical purity purposes, giving good primary peak resolution for sampling times between 200 and 1000 ms and low backgrounds to illuminate the presence of <1% impurity peaks.

Conclusions The development and testing has proven suitability for operation in the PET-QC environment. Current work is focusing on the integration of a compact digital pulse processor (DPP) to provide real-time spectrometric information and hence add an additional operational mode to the system.