Module 3 - Strategic case studies in practice

N- Nitrosodimethylamine (NDMA) and N- Nitrosodiethylamine (NDEA), with their volatile properties, can be well separated from confounding molecules under gas chromatographic or liquid chromatographic conditions. The latter also extends the range of analytes by including non-volatile or thermally instable N- nitrosamine (e.g. N- nitrosodiphenylamine), which can be measured by GC after time-consuming derivatisation steps only. Additionally, all review articles list adequate pre-purification and enrichment steps of N- nitrosamine from respective matrices, e.g. food, water, drug substances, etc., to reduce the complexity of compounds prior to analysis. Recently, a review was published summarising analytical methods utilised for the determination of N- nitrosamine in pharmaceuticals [Parr et al. (2019)], and information from the article can be gleaned to support guidance on analytical aspects. A rather new approach has been published in May 2019 describing the simultaneous determination of related substances and N-nitrosamines in valsartan and losartan [Schmidtsdorff et al. (2019)] in one chromatographic run only using supercritical fluid chromatography (SFC) with modifier (methanol and formic acid), combined with UV and electrospray ionisation (ESI) MS detection. This may have some advantages for routine control of N- nitrosamine. Special emphasis should be placed on the workup procedures prior to injection of the sample solution in either GC or LC in order to reduce potential interferences. While older literature describes laborious liquid-liquid extractions followed by concentration steps (with the risk to lose volatile N- nitrosamines), combined extraction and concentration can be achieved with solid-phase extraction (SPE) or solid- phase micro extraction (SPME). Several materials can be used for SPE. Published review articles [Perera (2006); Boyd et al. (2011)] discuss the advantages and disadvantages of different materials, either used alone or in combination. Activated carbon adsorbents are considered as suitable in general while reversed phase materials are deemed less effective. However, a combination of both increases the recovery of N- nitrosamines. SPME extracts the volatile or semi-volatile analytes from solutions with fused-silica fibre coated with a polymeric liquid phase. After equilibration, the adsorbed or absorbed analyte on the fibre is thermally desorbed in a hot injector port of a gas chromatograph or in an appropriate interface of a liquid chromatograph [Perera (2006)]. The hydrophilicity and consequently the solubility of the target analyte in water or other solvents should be taken into account, when elaborating the workup procedure. While NDMA and NDEA show a high-water solubility, the water solubility of NDPA and NDBA is lower. Some characteristics are given in table 2.3.2-1. Typical solvents used for extraction of N- nitrosamines are dichloromethane, methanol and acetone. 2.3.2. Sample Preparation Procedures

EMA/369136/2020

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