Identifying Contaminants in Manufacturing Processes Using an IR Microscope

All manufacturing processes are designed to create products that are made up of only the desired components. However, contamination frequently occurs and can effect the quality of the product and sometimes even results in product failure. A thorough investigation is needed to determine the nature of the contamination and its origin.

Infrared spectroscopy is a commonly used analytical technique for material analysis and identification. For contaminants that are large enough to be detected by the human eye, simple IR (macro) measurements can be performed. However, in industries such as electronics, contamination present at micro-level can cause issues in the final product.

IR microscopy allows samples as small as a few micrometers in size to be analyzed and identified and is the ideal solution for these types of problems. A range of sampling modes for the IR microscope (Attenuated Total Reflectance, transmission and specular reflectance) allow spectra measurements for contaminants present in a range of sample matrices.

This study examines the use of Spotlight™200i system, an automated IR microscope system, for detecting and measuring various contaminants present in manufactured samples.

Automated Contaminant Detection and Analysis on Electronic Contact

Electronic contacts need to be clean and free from contamination to avoid problems in operation. A sample was submitted for analysis that contained visible contaminants. It was positioned on the Spotlight 200i for collecting a ‘visible image survey’ of the whole contact. This is shown in Figure 1. Some contaminants were detected using the “Detect Particles” function of the Spectrum 10 software (Figure 1).

The Visible Image Survey and expanded region, Figure 1b, showing automatic detection of contaminants.

Figure 1. The Visible Image Survey and expanded region, Figure 1b, showing automatic detection of contaminants.

The reflectance backgrounds and the spectra for the fiber particles are recorded automatically by the software, as shown in Figure 2.

Reflectance spectra of two contaminant fibers.

Figure 2. Reflectance spectra of two contaminant fibers.

The spectra of the two materials is similar to the lower spectrum that displays an additional broad peak cantered around 700cm-1. The upper spectrum was identified as an acrylonitrile-butyl methacrylate copolymer by comparing it with a database of polymer and polymer additives spectra. Since the lower spectrum clearly has another component present it was subjected to a mixture search, which also detected the presence of tin oxide in the sample.

Fiber Contamination on a Pharmaceutical Tablet

A pharmaceutical tablet was observed to have visible contaminants present, appearing to be on the surface. However, how the contaminant was introduced remained unclear. The Spotlight 200i was used to observe the sample with the help of a visible image formed by reflectance as shown in Figure 3.

The contaminant was found to be fiber. The image shows that a large proportion of the fiber is embedded under the surface of the tablet and hence could not have simply fallen onto the surface post-manufacturing.

The visible image of a fiber embedded in pharmaceutical tablet.

Figure 3. The visible image of a fiber embedded in pharmaceutical tablet.

Since the fiber was embedded into the sample surface and enclosed in excipients, direct ATR measurement was not possible. This necessitated the physical removal of the fiber from the surface of the tablet and examination by placing on a KBr window, as shown in Figure 4. The spectrum measured via transmission is shown in Figure 5.

The visible image of the extracted fiber on KBr window

Figure 4. The visible image of the extracted fiber on KBr window

Transmission spectrum of fiber extracted from pharmaceutical tablet.

Figure 5. Transmission spectrum of fiber extracted from pharmaceutical tablet.

The spectrum obtained still contains spectral features (broad – OH in the region 3400 cm-1 and C-O band at ~1020 cm-1) due to the microcrystalline cellulose, one of the excipients. However, performing mixture search allowed the fiber material to be identified as a chlorinated polyethylene as shown in Figure 6.

Transmission spectrum of fiber extracted from pharmaceutical tablet.

Figure 6. Transmission spectrum of fiber extracted from pharmaceutical tablet.

Conclusion

Identification of minute contaminants that occur during the manufacturing process can be effectively performed via IR microscopy. This study illustrates the suitability of an automated IR microscope for the fast detection and measurement of contaminants. Automatic detection and identification of contaminants can be done using the Spectrum 10 software.

The process of identification is accelerated by the range of IR microscopy sampling modes that are capable of making in-situ measurements. In some cases, the contaminant needs to be removed by physical means to achieve a high quality spectrum that is devoid of matrix interference.

This information has been sourced, reviewed and adapted from materials provided by PerkinElmer.

For more information on this source, please visit PerkinElmer.

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