Structural Elucidation of Unknown Impurity

Impurity profiling is a critical aspect of pharmaceutical manufacturing, ensuring the quality and safety of drug products. The identification and characterization of unknown impurities are essential steps in this process, as they can pose potential health risks to patients. Here’s an overview of the techniques and procedures used for structural elucidation of unknown impurities in pharmaceutical products:

We employ a range of methods to separate impurities from your compound. Prior to purification, we may conduct experiments to enhance impurity levels through forced degradation reactions. Our goal is to purify or isolate the compound using techniques such as liquid-liquid extraction, normal phase or reversed-phase purification, semi-preparative HPLC, crystallization, etc., to obtain sufficient quantities of the impurity (ies). This will enable us to conduct analyses for their structural elucidation.

LC-MS, or Liquid Chromatography-Mass Spectrometry, combines liquid chromatography with mass spectrometry to analyze impurities both qualitatively and quantitatively. It is commonly used in impurity profiling due to its sensitivity, selectivity, and ability to provide detailed structural information. The Orbitrap Mass Spectrometer is a high-resolution mass spectrometer that is also used in impurity profiling for its ability to resolve complex mixtures, identify unknown impurities, and perform structural elucidation. Other hyphenated techniques, such as GC-MS, DSC, TGA and Elemental Analysis, can also be useful depending on the nature of the sample. Spiking studies involve adding known impurities to a sample to compare with pure standards, aiding in the identification of unknown impurities. In conclusion, hyphenated techniques like NMR (1H, 13C, DEPT, COSY, HMBC, HSQC…) , LC-MS, the HRMS, and spiking studies are valuable tools in impurity profiling due to their speed, ease of use, and ability to provide detailed structural information.

1. Investigation Approach:

  • Impurity Peak Reproduction: Replicating stress conditions within laboratories to reproduce impurity formation and increase corresponding chromatographic peaks.
  • Peak Recognition: Optimizing chromatographic methods to resolve and identify the peak of interest.

2. MS (Mass Spectrometry) Experiments:

  • MS and MS2 Experiments: Conducting mass spectrometry scans on the sample to identify ionizable species present under the peak, followed by fragmentation experiments on selected parent ions to hypothesize molecular structure.

3. Confirmatory Experiments:

  • Assaying putative identities using commercially available standards and customized analytical methods.

4. Impurity Isolation:

  • Evaluating the feasibility of preparative method scale-up, performing isolation cycles, and providing NMR characterization when needed.

5. Toxicological Risk Assessment:

  • Classifying impurities based on ICH M7 guidelines for hazard assessment involving database searches for carcinogenicity and bacterial mutagenicity data.

6. In Silico Prediction:

  • Utilizing in silico QSAR predictors for predicting toxicological profiles when relevant data from literature is not available.

7. Permitted Daily Exposure (PDE) Determination:

  • Deriving PDE for systemic toxicity based on substance-specific doses is unlikely to cause adverse effects with daily exposure over a lifetime.

8. Margin Of Safety (MOS):

  • Comparing PDE with Maximum Daily Intake (MDI) to determine MOS and associated toxicological concerns.

In summary, various analytical techniques such as mass spectrometry experiments, confirmatory studies, impurity isolation, toxicological risk assessment procedures including in silico prediction are employed for identifying unknown impurities in pharmaceutical products while ensuring patient safety through comprehensive structural elucidation processes.

Contact us