Small Molecule Identity and Purity Testing
Pacific BioLabs is committed to providing our clients with personalized testing support for manufacturing and lot release testing for small molecule products. Identity and purity/impurity testing are crucial requirements of a lot release testing program. As such, PBL offers a variety of testing methods to analyze if content of final drug products match client specifications and are free of contamination and impurities.
Testing Services for Identity and Purity
- HPLC (High-Performance Liquid Chromatography)
- Mass Spectrometry – LC-MS, LC-MS/MS, and TOFMS
- UV-Vis (Ultraviolet-Visible Spectroscopy)
- FTIR (Fourier Transform Infrared Spectroscopy)
- TLC (Thin-Layer Chromatography)
USP <621> Chromatography describes the use of high-performance liquid chromatography for qualitative and quantitative analyses. Following standardized guidelines, Pacific BioLabs uses HPLC retention times and readings from various detectors to verify identity against a reference standard. This is done by comparing the chromatogram with the reference peak. Discrepancies between the expected and experimental chromatograms may indicate sources of impurity within the lot. PBL has many validated HPLC method for currently marketed drug products. See these available methods here.
LC-MS (Liquid Chromatography Mass Spectrometry) is an accurate and reliable method of chemical analysis that combines the advantages of liquid chromatography and mass spectrometry. PBL has extensive experience in using LC-MS for identity and purity testing for lot release programs. Mass to charge ratios derived from this analytical technique can reveal molecular weight of each compound and therefore help with the identification of the analytes and impurities. PBL also owns two triplequads, LC-MS/MS units, which contains two mass spectrometers in tandem. The first mass spec filters the precursor ion and fragments it. The second mass spec unit filters the fragmented ions. The triplequads have enhanced specificity and sensitivity over LC-MS instruments.
Time of Flight Mass Spectrometry is typically provides better resolution than LC-MS/MS and has an advantage of LC-MS/MS when analyzing unknown compounds (such as unknown impurities) while the LC/MS/MS is best used for known compounds. TOFMS determines an ion’s mass-to-charge ratios based on time the ion takes to reach the detector. PBL has many validated mass spec method for currently marketed drug products. See these available methods here.
Spectrophotometric tests are critical for the identification of many chemical substances. The UV-Vis technique is described in both USP <857> Ultraviolet-Visible Spectroscopyand USP <197> Spectrophotometric Identification Tests. These tests yield absorption spectra that demonstrates rough identification of the formulation and any contamination. This method may be coupled with HPLC to detect multiple components in separated mixtures. At Pacific BioLabs, UV-Vis testing is often performed in conjunction with other tests, to confirm sample identity and purity.
Infrared spectroscopy is notably the most powerful test in confirming the identity of small molecules and pharmaceuticals. As written in USP <197>, “the IR absorption spectrum of a substance […] provides perhaps the most conclusive evidence of the identity of the substance that can be realized from any single test.” FTIR results may be used to compare multiple specific peaks in the IR spectrum with those of a reference standard, establishing a robust acceptance criteria. PBL also has access to a FTIR library that may be used to search and compare expected results and characterize the specimen and impurities.
Thin-layer chromatography is another chromatography technique that may be used to rapidly characterize a formulation’s or sample’s content. Due to differences in analyte properties and interactions between the mobile and stationary phase, mixtures can be distinguished by their retention factors. Comparison against a known reference standard may confirm or reject the identity and purity of the tested sample.
Case Study – Drug Combination Studies
Our analytical team has worked on several drug combinations over the past 30 years. Notably, the team has tested the impact of certain classes of drugs on others. They have developed methods to test the binding efficacy of a polymer drug with commonly used drugs and whether the polymer drug reduced their safety or efficacy profile. Our team used HPLC to measure drug concentrations in simulated gastric fluids. You can read the detailed case study here.
Read More About Small Molecule Identity and Purity Tests
- PBL’s Available Validated Methods
- PBL’s Learning Center – Pharmaceutical CMC Expectations
- PBL Blog – FTIR – A Helpful Tool to Determine Chemical Composition
- FDA Guidance for Industry – ANDAs: Impurities in Drug Products