Analysis of ink and paint using near-infrared spectroscopy

Importance of the Topic

Near-infrared spectroscopy (NIR) enables rapid, non-destructive analysis of chemical and physical properties in inks and paints, supporting real-time quality control from raw materials to finished products. Its ability to monitor components such as dyes, pigments, moisture, viscosity, and catalysts helps manufacturers reduce production failures, ensure product consistency, and optimize formulations.

Goals and Overview of the Study

This Application Bulletin (AB-411) presents five case studies demonstrating NIR spectroscopy applications in the ink and paint industry:

• Assessment of dye strength in aqueous solutions
• Qualitative detection of moisture in flush pigments
• Quantitative monitoring of moisture in yellow pigment
• Simultaneous analysis of color strength and viscosity in inks
• Detection of catalyst levels in black paint primer

Methodology and Instrumentation

The studies employed scanning across the 400–2500 nm region using various setups:

• Metrohm NIRSystems Model 5000 with liquid sampling system and transmission detector
• Model 5000 with reflectance modules (fiber-optic reflectance and interactance probes)
• Process Analytics Model 6500 with remote reflectance probe for in-application monitoring
• Recommended equivalents: NIRS XDS RapidLiquid Analyzer, XDS SmartProbe Analyzer, XDS RapidContent Analyzer, XDS Process Analyzer

Sampling modes included transmittance (liquid cuvettes), reflectance (powder in cups), and interactance for solids. Calibration models utilized specific wavelength bands (e.g., 1678 nm for dye, 1940 nm for moisture), with multivariate PLS regressions.

Main Results and Discussion

• Dye strength: NIR calibrations achieved 1 % standard error (SEC) for monitoring dye concentration (90–122 %).
• Moisture in pigments: Qualitative differentiation in flush pigments and quantitative moisture determination (0.3–2.6 %) with SEC ~0.1 %.
• Color strength and viscosity: PLS models in the visible-NIR range (430–800 nm) provided SEC of 1.6 for color strength and 0.2 % for viscosity.
• Catalyst in primer: NIR detected catalyst presence despite interference from titanium dioxide, indicating potential for process monitoring.

Benefits and Practical Applications

• Rapid, non-destructive measurements enable inline and at-line quality checks.
• Reduced sample preparation and chemical waste compared to wet-chemical methods.
• Consistent monitoring of raw materials, intermediate formulations, and finished products.
• Improved process control minimizes batch failures and optimizes resource use.

Future Trends and Potential Applications

Advances in instrumentation, such as miniaturized NIR sensors and integrated process probes, alongside machine learning algorithms, will expand real-time analytics capabilities. Future developments may include automated feedback loops in production lines and extended spectral databases for novel pigments and additives.

Conclusion

The feasibility studies in AB-411 confirm that NIR spectroscopy is a versatile and effective tool for comprehensive monitoring of ink and paint properties, delivering rapid, accurate, and non-destructive analysis throughout the manufacturing cycle.

References

No external literature references were provided in the source document.