A new two-strip TLC method for the quality control of technetium-99m mercaptoacetyl-triglycine (^99mTc-MAG3)

^99mTc-mercaptoacetyl-triglycine (^99mTc-MAG3) has been used for dynamic renal imaging since about 30 years. Free pertechnetate (^99mTcO₄), colloidal ^99mTc ((^99mTcO₂)_n), ^99mTc-tartrate (precursor), precomplexes (^99mTc-(MAG3)_x) and lipophilic ^99mTc-MAG2 are the main radiochemical impurities that may occur in the preparation. The total amount of these impurities has to be identified before release of the product for patient administration to guarantee patient safety and good image quality. The European Pharmacopoeia suggests a method based on high-pressure liquid chromatography analysis in combination with a paper chromatography. This analytical method is time consuming, expensive and requires specially trained technicians. As a consequence, it is not widely applied in nuclear medicine radiopharmacies.

We developed a simple method for radiochemical purity testing of ^99mTc-MAG3. The method is based on thin layer chromatography with two strips to be developed in parallel. Method validation was carried out in comparison to the official methods of the companies and to the European Pharmacopoeia method. It was tested on specificity, accuracy, robustness and precision.

The proposed method is able to identify and quantify the sum of all impurities occurring in the preparation, respecting the acceptance criteria for the radiochemical purity defined by the official methods. Hydrophilic and lipophilic compounds are identified separately and results are obtained within less than 20 minutes. Our method is simple, cost effective, fast and is suitable for employing dose calibrators or radiometric scanners.