Although the goal of any synthetic process is to create the pure desired product, the realities of chemical synthesis and manufacturing mean that impurities are often present in final products. These impurities may give rise to toxicities, which are the primary driving force behind careful impurities analysis. Understanding what these impurities are, whether in active pharmaceutical ingredients (API), excipients used in drug manufacturing, or in other areas of research and manufacturing, is important to assure the quality and safety of the finished product. Degradation products, either from storage or from exposure to environmental or operational conditions, are also an important area of interest.
Impurities in products often represent minor components, and the ability to detect these in the presence of significant product is a challenge. Once detected, the need to assign a structure to the impurity or degradantis the next challenge. Both of these challenges are aided by Orbitrap™ technology. The high sensitivity and wide dynamic range of the Thermo Scientific Orbitrap Elite MS means that even minor components can be detected and valuable data gathered, while MSn fragmentation aids in structure determination.
Comstock K, Stratton T, et al.
ASMS 2012 Poster
The detection of degradation products or impurities in a finished product requires that a representative sample of the product be prepared that reflects any and all impurities or degradants that might be present. The finished product or its constituent parts are not the target of the study; instead, the potentially very minor impurities and degradants are. Extraction/solvation of a powder or liquid product, either with a solvent suitable for (U)HPLC analysis or extraction with dilution to a suitable solvent, is a common basic approach.
Degradation studies, which are often performed through exposure of the material to elevated temperature, humidity, pH, ultraviolet light, and other stresses, provide an early indication of potential impurities that may arise over time.
Detection requirements for impurities and degradants are often very low (typically 0.1% for pharmaceutical agents). This level of detection is required in the presence of often overwhelming amounts of the desired product. Chromatographic separation prior to introduction to the mass spectrometer is important to assure that the impurities can be observed.
The sensitivity and wide dynamic range of Orbitrap™-based mass spectrometers allows for both the detection of, and the acquisition of fragmentation data on, these minor components. In addition, the fast scanning speed of the Thermo Scientific Q Exactive and Orbitrap Elite instruments allows for screening injections, where valuable fragmentation data is acquired on multiple components. Combined with the very high resolution and robust mass accuracy of Orbitrap mass spectrometers, the data gathered allows for the potentially related impurities and degradantsto be found in the sample. Re-acquisition using a targeted MSn fragmentation approach can be performed on peaks discovered through fragmentation searching. These structure identification injections can use a combination of CID and HCD fragmentation techniques on hybrid Orbitrap instruments, like the Thermo Scientific LTQ Orbitrap XL, Orbitrap Velos Pro, and Orbitrap Elite systems, to provide significant structure interpretation power.
Processing data obtained during impurities analysis and degradation studies can proceed through two major routes. For degradation products and impurities related to the product structure, a fragmentation-based search (Thermo Scientific Mass Frontier software version 7.0) can be utilized. This approach makes use of the fast scanning HCD MS2 data gathered on multiple precursors to identify potentially related materials for study.
For more complex products, where impurities may not be related to components of the product or degradants may arise from one or multiple components, a differential analysis approach is useful. The new lot or degradation sample is compared to a control analysis to detect small variation, which may be the result of impurities or degradants.
For either approach, the combination of high mass accuracy, high resolution, and accurate-mass MS/MS and MSn fragmentation provided by Orbitrap™ mass spectrometers enables identification through fragmentation analysis and library searching.
Here we show the detection of multiple trace impurities and degradation products in an active pharmaceutical ingredients (API) sample preparation through fragmentation analysis to detect related compounds and identify them, even those coeluting with the significant API peak.