Mass Spectrometry & Spectroscopy
Synergistic strategies for impurity and contaminant monitoring within healthcare industries
Dr Catherine Frankis, Reading Scientifi c Services Ltd (RSSL) The importance of impurity and contaminant analysis
Ensuring a product is free from unwanted contaminants and impurities is paramount in providing safe and effective healthcare products, whether these are pharmaceutical drugs or over-the-counter treatments. These issues can arise for several reasons including manufacturing process challenges, changes in raw materials or unexpected reactions of previously well characterised molecules within new formulation types. Additionally, the existence of fraudulent products can endanger patients’ lives from the absence of an active ingredient or the unconsidered substitution of cheaper agents designed to ‘bulk out’ or ensure positive test results against rudimentary analysis. Within three case studies, key considerations when planning analytical strategies in this area are highlighted and discussed.
Techniques and considerations
Chemical analyses in many forms have long been used to ensure the provenance, reliability and safety of products, however one analytical technique alone seldom provides suffi cient information to fully understand the identity of an impurity or contaminant, let alone the reason for its appearance. Possible techniques for investigation include chromatography (HPLC, GC, LC-MS), spectroscopy (NMR, FTIR, UV/Vis) and basic wet-chemistry methods. An issue will often require the holistic consideration of data from multiple techniques to gain a better picture of what, why, how and if possible, when the impurity/contamination fi rst arose.
It is important to consider sample preparation strategies when planning investigations, especially when the use of spectroscopic techniques is planned, or where instrument sensitivity is of concern. A range of techniques can be employed, building up in complexity, depending on the relative concentration of the impurity/contaminant and the nature of other ingredients present. Some analytical techniques lend themselves better to in-depth analysis of a single component in a complex matrix, while others require an isolated sample of high purity to provide best results. Conversely, it can also be of value to consider a sample on the analytical data collected from the sample in its whole (‘bulk’) state, where an analytical fi ngerprint of all compounds present can be assessed, either visually or statistically, to aid non-targeted impurity/contaminant screening.
Case Study: Identifi cation of an unknown impurity
in a pharmaceutical product Routine quality control (QC) analysis, commonly chromatography-based, can reveal unexpected peaks, which may indicate the presence of an unknown impurity. In these cases, it is crucial to understand the nature of the impurity to assess the toxicological impact on the product and to allow generation of a root cause hypothesis. The concentration of an unknown impurity in these instances may be low and so techniques which give superior sensitivity are often employed in the fi rst instance. An analytical HPLC method can be transferred to high accuracy LC-UV-MS in order to determine a mass ion for the unknown impurity, and therefore also a molecular formula, considering the presence of common adduct forms (e.g. sodium, ammonium). The isotope ratio of certain atoms will also give rise to distinctive patterns in the mass spectra; for example the natural abundance of 35
Cl and 37 Cl will indicate the number of chlorine
atoms present within an impurity structure. However, once generated, a molecular formula can give rise to a number of structural isomers. On some occasions, LC-MS/ MS can be used to look for tell-tale fragments, but in other instances, techniques that provide inherent structural information, such as NMR, can be harnessed. Consideration of observed splitting patterns and coupling constants observed within the 1
H NMR
spectrum can confi rm the structural identity of an unknown compound (Figure 1). As a fi nal confi rmation step, once an impurity molecule has been identifi ed, it can be
Figure 1: LC-UV chromatograms acquired from control (upper) and test (lower) samples, with impurity peak highlighted. Inset: LC-MS and NMR data used to aid structure elucidation.
analysed using the original HPLC method and the observed retention time will agree with the original unknown peak.
Case Study: Nitrosamines – analytical strategies
for mechanistic investigations In recent years, the pharmaceutical industry has become concerned about the formation of nitrosamines within products, which can be formed either intramolecularly or by reaction of selected functional groups with low level nitrate and nitrite compounds, commonly found in a broad range of excipient materials. As such, there is a need to screen raw materials for the presence of nitrate and nitrite at sub-ppm levels. HPIC (ion chromatography) with conductivity detection is a popular method for anion screening and recent advances in hardware and consumables available now mean that detection levels as low as 1 ppb can be achieved in solution. In certain materials, however, high levels of chloride may interfere with nitrite determination, and in such instances alternative detection methods, such as UV-visible absorption or MS, can be used (Figure 2). It’s also important to consider the effect of excipient properties on the performance of the analytical method; for example, water-soluble polymeric excipients (e.g. copovidone) can collect on the column and affect the method performance without suitable dilution and/or column clean-up procedures. Overall, this
INTERNATIONAL LABMATE - NOVEMBER 2023
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64
