Estudo da degradação de reagentes liofilizados para radiodiagnóstico por cromatografia líquida de alta eficiência (HPLC) e espectrometria de massas (MS)

Abstract

The use of radiopharmaceuticals in the diagnosis of diseases of the human organism has increased significantly in the last decades. The increasing development of new lyophilized reagents (LR) for the preparation of radiopharmaceuticals, although providing a greater variety of radiopharmaceuticals to the market, makes evident a gap in the radiopharmaceutical research: identification of degradation products. In the present work, the main degradation products of the 2,3-Dimercaptosuccinic acid (DMSA) and Ethylenedicysteine Diethyl Ester (ECD) LR were identified, using the techniques of high performance liquid chromatography with diode array detection (HPLC-DAD) and liquid chromatography multiple-stage mass spectrometry (LC-MS n). The study of forced degradation of DMSA and ECD LR was performed in the hydrolytic, photolytic and oxidative stress conditions and thermodegradation. Analyses were performed using an HPLC-DAD Shimadzu and mass spectrometer Bruker Daltonics equipment. All analyzes were carried out using Shim-Pack VP-ODS (150 mm x 4.6 mm; 5 μm) chromatographic column. DMSA showed a retention time of 5.58 minutes and m/z 204.8. Acid hydrolysis of DMSA showed no degradation products. The degradation profile of DMSA after alkaline hydrolysis presented three chromatographic peaks with more nonpolar characteristics than DMSA. In the fragmentation spectrum of the ion m/z 204.8 (MS 2), the presence of a fragment of m/z 172.9 was observed, corresponding to sodium adduct of mercaptosuccinic acid (MSA); and a fragment of m/z 139.0 (MS 3), corresponding to sodium adduct of fumaric acid. The tin ion was coordinated to DMSA in all degradation products after alkaline hydrolysis of DMSA LR. The samples submitted to neutral hydrolysis showed no degradation. In the studies of photolysis of DMSA, the ion m/z 267.1 can be related to diacetyl dimercaptosuccinic acid (BATSA). The ion of m/z 127.1 observed in the studies of oxidation can be related to phosphonic hydroxymethyl acid. The thermodegradation of DMSA and its LR did not show a relationship between the decrease in the DMSA concentration and the time. The protonated ECD was observed in 5.55 minutes (m/z 325.6). Analysis by LC-MS n of ECD under alkaline hydrolysis showed that the peak with retention time of 1.71 minutes could be identified as the protonated ion of EC ([M+H] +) at m/z 269.2. The peaks with retention times of 3.34 and 3.69 minutes were identified as the protonated ion of ECD in its monoester form (ECDM). The alkaline degradation of ECD LR presented the m/z 441.9 (ECD-Sn) and m/z 737.9 ([ECD 2 +Sn]-C 2 H 2-2H) ions. ECD monoester monoacid (ECDM) of m/z 295.2; ECD oxidized of m/z 323.5; ECD oxidized with two disulfide bonds of m/z 389.1 and ECD dimer of m/z 645.9 were observed in the oxidative degradation. It was concluded that the analysis by HPLC-DAD and LC-MS n can be used in the stability of LR, identifying and quantifying its impurities and degradation products.