Cancer is one of the leading causes of human death worldwide. Radiopharmaceuticals therapy (RPT), as a new cancer treatment method, has aroused widespread commercial interest and is highly recognized.

However, to avoid unnecessary radiation exposure caused by radioactive drugs, it is necessary to use targeted effects to deliver radioactive isotopes to the target lesion site. Usually, this targeting effect is achieved through two pathways: one is some radioactive isotopes with intrinsic targeting chemical properties called "organophilic substances", which naturally accumulate in specific organs or tumor tissues after entering the human body; Another type is RDC drugs, which are drug forms obtained by precisely coupling targeted molecules (monoclonal antibodies or peptides/small molecules, Ligand) and potent killing factors (nuclides, Radioisotopes) together with linker arms. By using antibodies or small molecules to mediate specific targeting, cytotoxic molecules or imaging molecules (such as radioactive isotopes) are delivered to the target site, so that the radiation produced by radioactive isotopes is concentrated on the local tissue, reducing the damage caused by whole body exposure to other tissues while achieving efficient and precise treatment. The energy carried by the radioactive rays produced by nuclides can damage the chromosomes of cells, causing them to stop growing and eliminating rapidly dividing and growing cancer cells. RDC payload is a radioactive nuclide that can be used for both diagnostic and therapeutic purposes.

The quality inspection of radioactive drugs is crucial, generally divided into three aspects: physical, chemical, and biological inspection. Among them, the physical inspection items include: observation of drug properties (color, clarity, particles, etc.), identification of radioactive nuclides, purity of radioactive nuclei, radioactive activity, etc; Chemical testing items include: determination of pH value of solutions or injections, radiochemical purity, chemical purity, etc; The biological testing items include: sterility, distribution and biological activity of pyrogen (bacterial endotoxin), etc.

In the research of radiopharmaceuticals, biodistribution testing, as a part of elucidating pharmacokinetics, is one of the necessary materials to be submitted; Biological distribution testing is also of great significance in the routine inspection of radioactive drugs. This test generally uses a gamma spectrometer. McNeil et al. [1] used ICP-MS/MS method to evaluate the purity of 161Tb in real time before product decay, providing a useful tool for quality control.

Chemical purity refers to the content of certain non radioactive chemical components in radioactive drugs. These non radioactive chemical components are generally introduced during the production process and may cause toxic side reactions or affect the further preparation and use of radioactive drugs in excess. Therefore, it is necessary to accurately measure them. The commonly used methods for determining chemical purity include titration, spectrophotometry, atomic absorption spectroscopy, etc. Since the determination of chemical purity is not related to radioactivity, it is possible to wait for the decay of radioactive isotopes for a period of time before conducting analysis, in order to reduce the radiation absorption dose borne by operators and the radioactive contamination of equipment, without rushing to obtain the determination results. However, most radioactive drugs are injections and oral solutions, and the presence of high organic phases and high salt content may not only introduce unknown chemical impurities, but also increase the difficulty of analysis.

This article uses the Agilent 7850 ICP-MS system to simulate various situations and detection requirements that may be encountered in the production process of radiopharmaceuticals using stable isotopes. It demonstrates the application of ICP-MS in radiopharmaceutical analysis from the aspects of substrate applicability, stability, sensitivity, and convenience.