FTIR in QA/QC Laboratories and on Manufacturing Floors

Significance of the topic

Fourier Transform Infrared (FTIR) spectroscopy has become a practical, high-value tool for quality assurance (QA) and quality control (QC) in industrial environments. Its strengths—rapid analysis, chemical specificity, minimal sample preparation (especially using ATR accessories), robustness, and compatibility with chemometric methods—enable on‑line, at‑line, and laboratory deployment. These features reduce turnaround time, permit routine screening by non‑specialist personnel, and provide economically attractive monitoring of production processes and final product quality.

Objectives and overview of the application note

The application note demonstrates how compact Thermo Scientific Nicolet FTIR spectrometers and a set of sampling accessories and software tools can be applied as dedicated QA/QC analyzers across multiple industrial use cases. The goal is to illustrate real‑world implementations for qualitative identification and quantitative determination, show how chemometrics simplify routine monitoring, and highlight examples where FTIR offers advantages over alternative techniques.

Methodology and approach

The document presents case studies that combine transmission and attenuated total reflectance (ATR) sampling with multivariate calibration (Partial Least Squares, PLS) and spectral difference techniques. Method development emphasizes: reproducible sample presentation (constant optical path length via ATR), selection of diagnostic absorption bands for univariate measurements, and creation of PLS models for complex matrices. Routine operation is optimized for single‑keystroke measurements and push‑button result reporting to enable use by non‑technical operators.

Instrumentation used

• Thermo Scientific Nicolet FTIR spectrometers (compact, rugged models suitable for QA/QC and production-floor environments).
• Horizontal ATR accessory for solids and liquids to provide constant optical path length and minimal sample preparation.
• TQ Analyst quantitative analysis software (for PLS calibration and rapid routine prediction).

Main results and discussion

The application note provides several representative examples showing FTIR performance in industrial QA/QC:

• Toluene diisocyanate (TDI) in pre‑polymer mixtures: ATR spectra show clear NCO band (~2,250 cm⁻¹) and carbonyl band (~1,700 cm⁻¹) enabling quantitative monitoring of TDI content prior to polymerization.
• Oxygenated gasoline extenders: Methanol, ethanol and MTBE produce distinct IR bands that permit straightforward detection and quantitation of extender concentration in fuel blends.
• Fluorinated polyethylene surface monitoring: CHF/CF₂ bands enable determination of surface fluorination levels; FTIR is presented as a cost‑effective and practical alternative to neutron activation analysis (NAA) and electron spectroscopy for chemical analysis (ESCA) for routine monitoring.
• Corn syrup process control: PLS calibration models (TQ Analyst) correlate spectral features with dextrose equivalent (DE) and dry substance (DS) values for rapid in‑process quality control.
• Lubricant blend characterization and used oil condition monitoring: Overlay and difference spectra reveal base oil and additive signatures and allow detection of oxidation products, fuel contamination, soot, water, glycols and other degradation markers. Difference spectroscopy vs. fresh oil simplifies detection of changes due to service exposure.
• Hydroxyl number in glycols: Variation in OH‑related absorptions across spectra correlates with hydroxyl value, which relates to molecular weight and functional performance of glycols.

Across examples, key practical observations include good sensitivity for organic functional groups, reproducible quantitation using ATR constant path length, and robust calibration when combined with chemometric techniques. The instrument’s internal wavelength calibration and high signal‑to‑noise support accurate, repeatable measurements suitable for production environments.

Benefits and practical applications

FTIR provides multiple operational advantages for QA/QC and manufacturing floors:

• Speed: fast spectral acquisition enables near‑real‑time decision making.
• Low cost of analysis: minimal consumables and rapid throughput reduce per‑sample cost.
• Minimal sample prep: ATR and other sampling interfaces reduce or eliminate extraction and complex handling.
• Operator simplicity: calibrated, push‑button methods support use by non‑specialists.
• Versatility: applicable to gases, liquids, and solids with appropriate sampling accessories.
• Chemometric integration: multivariate models (PLS) extend FTIR utility to complex matrices and enable accurate quantitative predictions.

Future trends and potential applications

Trends that will increase FTIR impact in industrial QA/QC include tighter integration with process analytics (PAT), expanded use of automated and in‑line ATR probes, cloud‑based model management, and improved chemometric toolsets enabling transfer of calibrations between instruments and sites. Miniaturization and ruggedization will broaden deployment directly on manufacturing floors, while ongoing improvements in software and multivariate diagnostics will make model maintenance and drift detection simpler for QA teams. Potential extended applications include lifecycle monitoring of lubricants across fleets, real‑time polymer surface treatment control, and inline monitoring of fermentation and bioprocess streams.

Conclusion

FTIR spectroscopy, implemented with rugged Nicolet instruments, ATR sampling, and chemometric software, offers an efficient, accurate and flexible platform for QA/QC and production monitoring. The technology combines speed, chemical specificity and operational simplicity to deliver reliable routine analyses across a wide range of industrial chemistries, often providing a cost‑effective alternative to more complex surface or elemental techniques.

References

• Thermo Fisher Scientific. Application Note AN50729_E (2024) FTIR in QA/QC Laboratories and on Manufacturing Floors.