FTIR Applications in the Chemical Industry: Raw Material Identification and Quality Control

Raw Material Identification and Quality Control from an Instrument Supplier’s Perspective

In the chemical industry, raw material quality is the foundation of product consistency, process stability, and operational safety. Incorrect material identification, grade mismatch, or hidden adulteration can lead to reaction failure, batch rejection, equipment fouling, and even serious safety incidents.

Fourier Transform Infrared Spectroscopy (FTIR) has become a core analytical technique for raw material inspection (IQC) due to its advantages of speed, non-destructive analysis, high sensitivity, and strong chemical specificity.
By detecting the characteristic infrared absorption of functional groups, FTIR generates unique “molecular fingerprint spectra”. Combined with professional spectral libraries and quantitative calibration models, FTIR enables chemical manufacturers to implement fast, reliable, and cost-effective raw material quality control at the source.

Why FTIR Is Ideally Suited for Chemical Raw Material Control

Chemical raw materials cover a broad and complex range, including:

• Organic materials: alcohols, ethers, esters, hydrocarbons, monomers, polymers
• Inorganic materials: salts, oxides, carbonates, silicates, hydroxides
• Composite materials: resins with fillers, additives, modifiers

These materials may appear as solids, liquids, or gases, often requiring different analytical approaches.

FTIR technology offers outstanding adaptability across all these scenarios:

• Minimal sample preparation
• Direct analysis of solids, liquids, and gases
• Compatibility with laboratory, production-line, and on-site testing

As a result, FTIR has become a standard analytical tool in chemical IQC systems, process verification, and troubleshooting workflows.

Qualitative Identification and Authenticity Verification of Raw Materials

Precise Identification of Organic Chemical Raw Materials

Many organic raw materials exhibit similar physical properties but differ in functional groups and molecular structures. These differences directly influence downstream reactions and final product performance.

FTIR enables rapid differentiation based on characteristic absorption peaks, for example:

• Alcoholes
  • Methanol: broad –OH absorption around 3300 cm⁻¹, C–O stretching near 1030 cm⁻¹
  • Ethanol: –OH around 3350 cm⁻¹, C–O near 1050 cm⁻¹
• Ésteres
  • Ethyl acetate: C=O stretching at ~1740 cm⁻¹
  • Butyl acetate: C=O near 1735 cm⁻¹ with stronger long-chain C–H absorption at ~2960 cm⁻¹
• Aromatic compounds
  • Benzene: ring vibration peaks at ~1600 and 1500 cm⁻¹
  • Toluene: additional methyl C–H absorption near 2920 cm⁻¹

By comparing measured spectra with professional reference libraries such as Sadtler or NIST, FTIR can typically achieve reliable qualitative identification within minutes, with matching confidence levels above 90%.

Polymer and Resin Type Confirmation

High-molecular materials such as PE, PP, PVC, epoxy resins, polyurethane, and phenolic resins often differ in branching degree, crosslinking density, or functional group content. These differences are clearly reflected in infrared spectra.

Typical applications include:

• PE grade identification
  • LDPE shows a pronounced methyl bending vibration at ~1370 cm⁻¹
  • HDPE exhibits a significantly weaker peak at the same position
• Polipropileno (PP)
  • Strong and characteristic methyl absorption around 1370 cm⁻¹, allowing rapid distinction from PE
• Epoxy resins
  • Epoxy ring absorption at ~910 cm⁻¹ confirms the presence and integrity of epoxy functional groups

FTIR allows manufacturers to verify resin type and structure before use, preventing formulation failure caused by incorrect or degraded materials.

Detection of Adulteration and Raw Material Fraud

Adulteration and grade substitution remain common risks in the chemical raw material supply chain. FTIR provides an efficient screening method by identifying unexpected peaks or abnormal intensity changes.

Typical examples include:

• Glycerol adulteration
  • Pure glycerol shows a strong, broad –OH band near 3300 cm⁻¹
  • Water addition introduces a bending vibration near 1640 cm⁻¹
  • Ethylene glycol causes noticeable shifts in C–O absorption
• Silicone oil contamination
  • Pure polydimethylsiloxane exhibits strong Si–CH₃ (~1260 cm⁻¹) and Si–O–Si (~1090 cm⁻¹) peaks
  • Mineral oil adulteration introduces strong aliphatic C–H absorption near 2920 cm⁻¹
• Food- and pharma-grade chemicals
  • Industrial-grade impurities generate additional characteristic peaks, enabling rapid compliance screening

Identification of Inorganic Chemical Raw Materials

FTIR is also highly effective for inorganic compounds containing covalent bonds:

• Calcium carbonate (CaCO₃)
  • CO₃²⁻ asymmetric stretching at ~1420 cm⁻¹
  • Out-of-plane bending at ~875 cm⁻¹
• Silicon dioxide (SiO₂)
  • Strong Si–O–Si stretching near 1080 cm⁻¹
  • Bending vibration around 460 cm⁻¹
• Raw material degradation monitoring
  • Sodium hydroxide absorbing CO₂ to form Na₂CO₃ can be detected via emerging carbonate peaks

This capability is particularly valuable for monitoring moisture absorption and storage-related deterioration.

Technical Advantages of FTIR for Chemical IQC

Compared with GC, HPLC, and NMR, FTIR offers several irreplaceable advantages in raw material quality control:

• High analysis speed
  Complete identification typically requires only 1–5 minutes, ideal for batch IQC and production-line screening
• Broad physical-state compatibility
  Solids, liquids, and gases can be analyzed directly with simple preparation
• Non-destructive or minimal-damage testing
  ATR-FTIR enables direct measurement without altering valuable samples
• Low operating cost
  No consumable columns, mobile phases, or reference reagents required
• On-site and online monitoring capability
  Portable FTIR systems support warehouse and field inspections
  Online FTIR enables real-time pipeline monitoring
• High chemical specificity
  “Molecular fingerprint” spectra allow reliable differentiation of structurally similar materials

Practical Application Guidelines for Reliable Results

From an instrument supplier’s perspective, correct methodology is as important as instrument performance:

1. Sample preparation control
   Avoid contamination, moisture interference, and volatilization effects
2. Prefer ATR-FTIR for routine IQC
   Ideal for viscous, high-boiling, or insoluble materials
   Ensure ATR crystal cleanliness to prevent cross-contamination
3. Use application-specific spectral libraries
   Industry-focused libraries significantly improve identification accuracy
   Build in-house libraries for proprietary or new materials
4. Quantitative calibration discipline
   Select interference-free characteristic peaks
   Regularly recalibrate using certified reference materials
5. Mixed organic–inorganic systems
   Apply background subtraction or differential spectroscopy to isolate organic components

Typical Industry Applications

• Plastics & Polymers
  Resin grade identification, residual monomer detection, recycled material screening
• Coatings & Inks
  Resin and solvent identification, moisture and impurity monitoring
• Fine Chemicals
  Purity verification of flavors, fragrances, and food additives
• Rubber Industry
  Rubber type identification, antioxidant and additive content analysis
• Inorganic Chemicals
  Filler identification, moisture absorption and degradation detection

Instrument Configuration and Application Matching

Laboratory, IQC, and Production-Line FTIR Deployment

The effectiveness of FTIR in chemical raw material quality control depends not only on the analytical principle, but also on proper instrument configuration matched to specific application scenarios.
Different inspection environments impose different requirements on sensitivity, robustness, automation level, and data handling capability.

From an instrument supplier’s perspective, FTIR systems for chemical applications can typically be configured for three primary scenarios: laboratory analysis, incoming quality control (IQC), and production-line monitoring.

Laboratory FTIR Configuration

Typical application objectives

• Raw material qualification and method development
• Reference spectrum acquisition and library construction
• Quantitative model development and validation
• Root-cause analysis for quality deviations

Recommended configuration

• Bench-top FTIR spectrometer
• Wide spectral range (typically 4000–400 cm⁻¹)
• High spectral resolution (≤ 4 cm⁻¹)
• Multiple sampling accessories:
  • ATR (diamond or ZnSe)
  • Transmission cells (liquid and gas)
  • Diffuse reflectance (DRIFTS) for powders

Key advantages

• High analytical flexibility
• Best suited for complex material systems and method optimization
• Supports in-house spectral library creation for proprietary materials

Implementation guidance

Laboratory FTIR serves as the technical foundation of the quality control system.
Spectral libraries, acceptance criteria, and quantitative calibration models developed in the laboratory can later be transferred to IQC and production environments.

FTIR for Incoming Quality Control (IQC)

Typical application objectives

• Rapid verification of raw material identity
• Grade and supplier consistency checks
• Adulteration and contamination screening
• Batch release decision support

Recommended configuration

• Bench-top or compact FTIR system
• ATR-FTIR as the primary sampling mode
• Pre-configured identification workflows
• Integrated spectral library matching software

Key advantages

• Analysis time typically within 1–3 minutes per sample
• Minimal sample preparation
• Low operator dependency
• High repeatability for routine inspection

Implementation guidance

For IQC environments, robustness and simplicity are prioritized over maximum resolution.
Standardized ATR procedures and predefined pass/fail criteria help ensure consistent inspection results across operators and shifts.

FTIR for Production-Line and On-Site Monitoring

Typical application objectives

• Real-time verification of raw material feed
• Detection of abnormal composition during transfer
• Continuous quality monitoring
• Early warning of contamination or degradation

Recommended configuration

• Industrial-grade or portable FTIR system
• ATR flow cells or gas cells for inline measurement
• Automated data acquisition and alarm functions
• Integration with DCS or MES systems (optional)

Key advantages

• Immediate feedback without sampling delays
• Reduced risk of unqualified materials entering production
• Supports preventive quality control strategies

Implementation guidance

Production-line FTIR systems should emphasize mechanical stability, environmental tolerance, and data reliability.
Automated trend analysis and threshold-based alarms are recommended to support real-time decision-making.

FTIR Selection Guide for the Chemical Industry

A Practical Framework for Instrument Selection

Selecting the appropriate FTIR system for chemical applications requires balancing analytical requirements, operational conditions, and long-term quality objectives.
The following framework provides a structured approach for instrument selection.

Define the Primary Application Purpose

Application Focus	Recommended FTIR Type
Method development / R&D	High-resolution bench-top FTIR
Routine IQC inspection	ATR-based bench-top or compact FTIR
Warehouse / field inspection	Portable FTIR
Continuous monitoring	Online or process FTIR

Sampling Mode Selection

• ATR (Attenuated Total Reflection)
  Preferred for most chemical raw materials
  Suitable for solids, liquids, viscous samples, and insoluble materials
• Transmisión
  Suitable for pure liquids and gases with known path length
  Higher quantitative accuracy in controlled conditions
• Reflectancia difusa (DRIFTS)
  Suitable for powders and inorganic materials

In chemical IQC, ATR-FTIR is generally recommended as the default configuration due to its simplicity and versatility.

Spectral Performance Requirements

Key parameters to consider:

• Spectral range: Must cover target functional groups
• Resolution: Typically 4 cm⁻¹ is sufficient for IQC; higher resolution for research applications
• Signal-to-noise ratio (S/N): Critical for detecting low-level impurities

Higher performance specifications should be selected only when justified by application needs, to optimize cost-effectiveness.

Software and Data Management Capabilities

For industrial users, software functionality is often as important as optical performance.

Recommended features include:

• Automated library matching and similarity scoring
• User-defined acceptance thresholds
• Quantitative analysis and trend monitoring
• Audit trail and data integrity support
• Multi-user permission management

Scalability and Standardization

Chemical enterprises often expand FTIR usage over time.
Instrument selection should consider:

• Consistency of spectral data across different instruments
• Transferability of libraries and calibration models
• Compatibility between laboratory, IQC, and production systems

A standardized FTIR platform simplifies training, maintenance, and quality system integration.

Supplier Perspective: Building an Application-Driven FTIR Solution

From an instrument supplier’s standpoint, successful FTIR implementation is not limited to instrument delivery. It includes:

• Application assessment and configuration recommendation
• Method and workflow guidance
• Library and model transfer support
• Long-term technical service and application updates

By aligning instrument configuration with real industrial applications, FTIR becomes not just an analytical tool, but a core component of chemical quality management systems.

Conclusión

With its molecular fingerprint capability, rapid analysis speed, and versatility across material states, FTIR has become an indispensable analytical tool for chemical raw material identification and quality control.

From initial qualitative confirmation and authenticity verification to impurity screening, stability assessment, and deterioration warning, FTIR supports the entire raw material quality control workflow.
For chemical manufacturers, implementing FTIR-based IQC not only improves inspection efficiency and reduces testing costs, but also prevents unqualified materials from entering production at the source, ensuring consistent product quality and operational safety.

As an experienced FTIR instrument supplier, we focus not only on instrument performance, but also on helping customers build reliable, application-driven analytical solutions that truly support industrial quality management.

Referencias

1. ASTM E1252-98(2021) — Standard Practice for General Techniques for Obtaining Infrared Spectra for Qualitative Analysis
   This ASTM standard describes best practices for qualitative infrared spectral analysis of materials, covering solids, liquids, and gases. It is widely cited in industrial FTIR methodology.
   🔗 https://webstore.ansi.org/standards/astm/astme1252982021
2. ASTM D6348-12(2020) — Standard Test Method for Determination of Gaseous Compounds by Extractive Direct Interface FTIR Spectroscopy
   This standard provides a method for multicomponent gas analysis using FTIR, illustrating applications of extractive and interfaced FTIR methods.
   🔗 https://store.astm.org/d6348-12r20.html
3. NIST — Fourier Transform Infrared Spectroscopy
   The National Institute of Standards and Technology (NIST) provides a general overview of FTIR principles and capabilities, including functional group analysis and use of ATR accessories.
   🔗 https://www.nist.gov/laboratories/tools-instruments/fourier-transform-infrared-spectroscopy
4. Smith, Brian C. (2011) — Fundamentals of Fourier Transform Infrared Spectroscopy (2nd Edition)
   A well-regarded technical book covering FTIR theory, instrumentation, and analysis techniques. Available from CRC Press / Routledge, often used as a reference in spectroscopic method development.
   🔗 https://www.routledge.com/Fundamentals-of-Fourier-Transform-Infrared-Spectroscopy/Smith/p/book/9781420069297
5. Springer Handbook Chapter on FTIR Fundamentals
   An academic chapter on FTIR fundamentals and applications in functional group characterization, often used in materials and analytical spectroscopy research.
   🔗 https://link.springer.com/chapter/10.1007/978-3-319-92955-2_9
6. Wikipedia — Fourier-transform Infrared Spectroscopy
   A technical and referenced overview of FTIR principles, interferometer design, and typical applications. Useful as a concise technical reference summary.
   🔗 https://en.wikipedia.org/wiki/Fourier-transform_infrared_spectroscopy