Outsource Critical Cleaning: Contract Labs can do a better job of testing for contaminants
Pharmaceutical Formulation and Quality
March 1, 2009
Written by Barbara E. Blaum
After each batch of drug is produced, pharmaceutical manufacturers must ensure that the quality of the next product is not compromised by contaminants from the previous product’s production run. The subsequent cleaning process is intended to remove the residues of the active pharmaceutical ingredient (API) and excipients, along with plastic or metal wear particles from the machinery, cleaning agents from the cleaning process, and microbial contaminants. Unfortunately, the presence of contaminants is often not discovered until the following production run.
Despite strict cleanliness regulations for all parts of the drug development and manufacturing processes, cleaning manufacturing equipment between runs does not always remove 100% of the debris. When contaminants make their way into the next product, validation is impossible, and either manufacture or release of the drug must come to a halt. The problem is compounded when the company’s internal laboratory cannot identify the residual contaminants due to lack of appropriate analytical instrumentation or properly trained staff.
When this situation arises, pharmaceutical companies must outsource to contract laboratories. Unlike many pharmaceutical companies, which require a sterile cleanroom for drug production, the analytical laboratory’s cleanrooms restrict the number of particles in the air to ensure a low particle environment. This procedure allows the labs to isolate and identify contaminants without fear of further contamination.
Points of Vulnerability
Potential residues that can be left on critical pharmaceutical manufacturing surfaces as a result of the cleaning process include detergent residue, fibers from cleaning wipes, production machinery oil, latex glove fragments, and wear particles from machinery or tank corrosion products. These contaminants can enter the manufacturing process at any time, but some stages are more vulnerable than others. For example, during heat-intensive sterilization of parenteral vials or syringes, fibers or other organic traces left in the vials may become charred and fixed to the vial surface and subsequently transferred to the pharmaceutical product upon filling.
Analyzing and identifying these contaminants—as well as determining their sources—often leaves in-house quality control laboratories stumped. Independent analytical or microanalysis laboratories, on the other hand, can use sophisticated analytical instrumentation to characterize the contamination and identify the possible source.
Typically, after receiving a sample containing an unknown contaminant, microanalytical laboratories first perform a visual inspection. This is followed by an inspection using a stereomicroscope and, in some instances, a polarizing light microscope.
After viewing the contaminant and measuring its physical properties, lab technicians can often make an immediate assessment of the problem—or at least an educated guess. The presence of fibrous materials, for example, may indicate contamination from cleanroom wipes or garments, metal flakes may point to wear particles from production machinery, clumps of embedded granular material in tablets may be normal tablet ingredients but in a concentrated form, and discoloration of the contaminant could mean thermal degradation of the product.
After viewing the contaminant with a microscope and gathering as much information as possible, technicians then transfer samples to a specialized cleanroom where the contaminant is isolated from the product or substrate material and prepared for additional microanalysis. Sample preparations performed in a cleanroom can ensure that cross-contamination does not occur during the isolation or sample preparation process.
Cleanroom classification is based on the number of particles in the air. For example, in a Class 100 (ISO 5) cleanroom environment, there are no more than 100 particles per cubic foot of air ≥ 0.5 μm. By comparison, a regular laboratory environment can have millions of particles in the air at any time.
When contaminants make their way into the next product, validation is impossible, and either manufacture or release of the drug must come to a halt. The problem is compounded when the company’s internal laboratory cannot identify the residual contaminants due to lack of appropriate analytical instrumentation or properly trained staff.
At McCrone Associates, the microanalysis lab division of The McCrone Group (Westmont, Ill.), skilled microscopists routinely locate and isolate solid contaminants (particles or fiber fragments) as small as 1–2 μm in size. Isolation of contaminants smaller than 1–2 μm can also be performed but usually requires special techniques to ensure the integrity of the material.
If the contaminant is in a liquid such as sterile solution or rinse water, the liquid is filtered and the contaminant particle is isolated onto a polycarbonate membrane filter in order to aid in characterization and isolation of the particulate. To ensure the integrity of the sample—so that no contaminants are inadvertently added—the filtration process takes place in a Class 100 hood within a Class 100 cleanroom. When the contaminant is identified, the source can be determined and the problem solved.
Isolation is Everything
Special tools such as fine tungsten needles are used to isolate the contaminant material and prepare it for analysis. These needles, far smaller than commercial dissecting needles, are handmade by microscopists and are a few micrometers thick at the tip (see figure, p. 20). The needles are essential to isolation, and, as with most things, the proper tools are critical to getting the job done.
One of the great advantages of microanalytical testing is that, rather than sacrificing an entire sample, only a minute portion is required, and the area from which this portion is removed is often unnoticeable. Furthermore, isolating the offending contaminant from its surroundings makes it easier to identify.
One pharmaceutical company found traces of corroded stainless steel in its final product and determined that some unknown substance was attacking its stainless steel mixing basins. Unable to isolate the contaminant from the substrate or background material, the company could only identify the apparent source of the contaminant, not its cause.
After McCrone Associates was given a swab sample, the material was isolated and characterized in the cleanroom. Analysis of the contaminant using energy dispersive X-ray spectrometry (EDS) detected high levels of chlorine, indicating that the high concentration of chlorine in the cleaning agent the company used was corroding the tanks.
Most analyses require isolation of the contaminant from the original sample and remounting on a different substrate for microanalysis. Depending upon the instrument needed for analysis, the substrate will vary (e.g., elemental analysis in an electron microprobe requires a polished carbon substrate, whereas for infrared analysis a polished salt crystal is required). Subsequent analysis of the contaminant using a variety of methods requires moving the contaminant from substrate to substrate. Each contaminant must be treated uniquely, and proper isolation and sample preparation within a cleanroom setting is the only way to ensure its integrity.
In addition to the light microscope, the two most commonly used analytical techniques for the analysis of pharmaceutical contaminants are Fourier transform infrared microspectroscopy (FTIR or micro-FTIR) and scanning electron microscopy (SEM) combined with EDS for elemental analysis.
One of the great advantages of microanalytical testing is that, rather than sacrificing an entire sample, only a minute portion is required, and the area from which this portion is removed is often unnoticeable.
FTIR can be used to identify organic as well as some inorganic materials. As substances absorb light at different frequencies, each one produces a unique infrared spectrum, a chemical fingerprint of the material. To prepare a sample for micro-FTIR analysis, a portion of the contaminant as small as 10 µm is isolated by hand and pressed thin onto a potassium bromide crystal. The micro-FTIR system, a polarizing light microscope interfaced with an infrared spectrometer, shines a beam of infrared radiation through the sample and records the different frequencies at which the sample absorbs the light.
McCrone Associates maintains an FTIR reference library of thousands of known materials. By comparing the spectra of known materials through an automated computer search with the spectrum from the contaminant, scientists can often identify the contaminant.
The SEM/EDS method results in two kinds of information: a high-quality morphological image showing the features of the contaminant and a spectrum of the elemental constituents present in the sample. EDS is commonly used for the analysis of inorganic materials to identify contaminants such as metals, glass fragments, and minerals. It can also be used to characterize certain organic materials, particularly if they contain elements other than carbon and oxygen, including silicone rubber stopper fragments or tablet materials that contain metal salts. EDS analysis may also provide a clue as to the identity of charred contaminants. For instance, the presence of sulfur may indicate that the charred substance was a component of the API if the API also contained sulfur.
Upon completion of the analysis and identification of a contaminant or defect, the laboratory provides the customer with a detailed report that includes a summary of the analyses performed, photographs taken during the analysis, raw data (spectra), and a summary of the data evaluation and interpretation. The report provides the identity of the contaminant along with its possible sources based upon its composition and the information gathered from discussions with the client. The report cannot serve as validation of the cleaning process, but it can help companies determine a comprehensive cleaning process and can aid in the investigation to pinpoint contamination problems.
Blaum is a vice president and director of quality assurance and light microscopy at McCrone Associates Inc., the analytical service division of the McCrone Group. Reach her at firstname.lastname@example.org or (630) 887-7100.