Category: Formulation and Quality
Purpose: The presence of foreign particulate in parenteral products frequently sparks an investigation to determine the particulate source. Root cause analysis (RCA) is an investigative tool for evaluating the reason for a deviation or nonconformance. Characterization of foreign particulate in a parenteral product is a critical step in RCA. The more information known about the particulate, the more likely a source of the particulate can be found and corrective and preventative action can be taken. Using multiple techniques for particulate characterization concurrently not only increases the knowledge of the particle but streamlines the workflow in the laboratory to decrease time and resource utilization. An investigation requires a sound scientific approach, experienced scientists, rapid analysis and complementary techniques to determine the source of the foreign particulate.
Methods: Isolation of the particles was conducted under an ISO 5 clean bench using vacuum filtration onto a polycarbonate membrane filter. The filter was examined using darkfield reflected light microscopy and differential interference contrast microscopy (DIC) to determine particle size, morphology and general appearance. Polarized light microscopy (PLM) was used to characterize optical properties. Subsamples of particulate were removed from the filter and transferred to various substrates for chemical and elemental analysis. Chemical information was acquired using Fourier transform infrared microspectroscopy (FTIR) and confocal Raman microscopy (CRM) which revealed the particulate was foreign material and did not originate from the drug product. Elemental analysis using scanning electron microscopy with energy dispersive x-ray spectrometry (SEM-EDS) characterized the foreign particulate as aluminum corrosion products. Based on the characterization of the isolated particulate, the manufacturer sent samples from a possible source for comparison. The particulate submitted by the manufacturer was analyzed using the same techniques and parameters as the original sample.
Equipment: Nikon Eclipse LV100 DIC and darkfield microscope, aus Jena Jenapol polarized light microscope, SensIR IlluminatIR Fourier transform infrared spectrophotometer coupled to an Olympus BX51 compound microscope, Renishaw inVia confocal Raman microscope, JEOL JSM-6500F field emission scanning electron microscope coupled to a Thermo Scientific Noran System 7 spectral imaging system.
Results: The sample presented as a glass vial containing visible suspended particulate in a colorless solution. Suspended particles were isolated by filtration and imaged using multiple contrast-enhancing techniques. Darkfield reflected light microscopy created contrast between the filter and the thin colorless particles, allowing the visualization of the particles’ true appearance. Isolated particles ranged from 50 to 400 micrometers (µm). DIC microscopy of both samples revealed the particles exhibited bireflectance typical of thin particles. PLM analysis of each sample revealed the particles were low birefringent polycrystalline flakes. FTIR analysis of each sample revealed strong absorbance at approximately 3200-3600 wavenumbers (cm-1) in the O-H stretch region suggesting the particulate contained a hydroxide or hydroxyl functional group. Raman analysis of each sample revealed a sharp peak at approximately 545 cm-1 similar to inorganic salts and corrosion products. SEM-EDS analysis of each sample revealed the particles were composed of oxygen and aluminum with trace amounts of carbon and chlorine.
Conclusion: The particles from the parenteral product and the sample submitted by the manufacturer were aluminum corrosion products likely from the same source. The SEM-EDS analysis results were consistent with the FTIR and Raman analysis results. Simultaneous analysis of each sample using multiple techniques allowed the analyses to be completed on the same day the samples were received. Applying multiple analytical techniques to the same set of particles served as a quality check between techniques ensuring that the results were accurate. The parenteral product was protein based and did not contain ingredients with aluminum, so the isolated particulate was classified as extrinsic, or not part of the formulation, packaging, or assembly process. Discussions with the manufacturer identified a source of the aluminum corrosion products and provided vital information in determining the root cause of the foreign particulate.