Analysis of Contaminations on a Plastic Part using the FT-IR Microscope LUMOS II

Significance of the topic

The analysis of microscopic contaminations on polymer products is critical for ensuring product integrity and identifying sources of defects. FT-IR microscopy provides chemical specificity for both organic and inorganic residues at high spatial resolution, enabling direct identification of contaminants without extensive sample preparation.

Objectives and overview of the study

This application note demonstrates the use of the stand-alone FT-IR microscope LUMOS II to analyze black streaks on a polycarbonate part. The aims are to determine whether the streaks reside on the surface or are embedded and to identify their chemical nature to trace their origin.

Methodology

A fully automated protocol was applied using attenuated total reflectance (ATR) mapping with a motorized Germanium ATR objective. Six measurement points were selected on the contaminated area and on a clean reference region. Spectra were acquired with 4 cm⁻¹ resolution and 17 s acquisition time per point. A difference spectrum was generated by subtracting the polycarbonate matrix signal from the contaminated spot spectrum.

Used instrumentation

• LUMOS II FT-IR microscope with integrated spectrometer
• 8× ATR Germanium objective for transmission, reflection and ATR modes
• Motorized sample stage and automated OPUS Video-wizard interface

Key results and discussion

Spectral comparison showed clear differences between the black spots and the polycarbonate background. The difference spectrum revealed characteristic bands matching a black ink marker (marker ink black 6558) via library search. This identification confirms that the contamination originated from ink, allowing corrective action in the production or handling process.

Benefits and practical applications

• Stand-alone, compact design minimizes laboratory footprint and complexity
• Fully automated ATR mapping reduces user skill requirements
• High lateral resolution (four-fold improvement in ATR) and strong surface sensitivity
• Built-in library search accelerates identification of unknown contaminants
• Suitable for QC in polymers, electronics, mechanical parts and pharmaceuticals

Future trends and possibilities

Advances may include integration of artificial intelligence for automated pattern recognition, expanded spectral libraries for broader contaminant coverage, improvements in spatial resolution and coupling with complementary techniques (e.g., Raman microscopy). Real-time in-line monitoring and miniaturization of microscopy systems will further enhance contaminant control in manufacturing environments.

Conclusion

The LUMOS II FT-IR microscope offers an accessible, high-performance solution for surface defect and contamination analysis. Its automated ATR mapping and intuitive software enable rapid identification of minute residues, supporting effective quality assurance and root-cause investigations across diverse industries.