To investigate an unknown peak at relative retention time (RRT) 0.95 of N-nitrosodiethylamine (NDEA) of irbesartan API with the LC-MS/MS detection method. To elucidate the structure and origin of this unknown peak. Its structure was confirmed with a reference compound, and a method optimization strategy was proposed to eliminate the impact of this unknown peak.
The unknown peak causing interference in the determination of NDEA within sartan drug substances was examined using a full scan method of LC-MS/MS analysis. The unknown peak at RRT 0.95 was validated by conducting high resolution LC-MS analyses and comparing with that of a reference sample. Additionally, a strategy for resolving this issue was proposed in the further investigation.
According to the LC-Q TOF MS results, the unknown peak at RRT 0.95 was confirmed to be 1-pentanamide, a trace regular impurity commonly existing in the sartan samples. As the extract mass of 1-pentanamide was 1 less than that of NDEA, the m/z value of an isotope in 1-pentanamide ([M+H]++1) was 103 and was equal to the m/z value of the main [M+H]+ isotope of NDEA under the MRM mode. Furthermore, the [M+H]++1 isotope ion of 1-pentanamide could occur a neutral lose by leaving a molecule of ethylene to generate the isotope ion of m/z 75, which was similar to NDEA in the MRM analysis under ESI positive mode. Therefore, when m/z 103 was used as the precursor ion and m/z 75 was used as the quantitative ion, 1-pentanamide will interfere with detection of NDEA.
In the LC-MS/MS analysis for NDEA, the unknown peak observed at a retention time of 0.95 has been identified as 1-pentanamide. This compound is confirmed as a common trace impurity that regularly occurs during the production of sartan active pharmaceutical ingredients (APIs), rather than being another nitrosamine impurity. Subsequent research has revealed that employing a more selective quantitative model and choosing m/z 47 as the quantifier ion effectively avoid the unknown peak caused by 1-pentanamide.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |