Industrial laboratories are under constant pressure to deliver accurate QA/QC results faster while keeping routine analysis practical for laboratory personnel.
For some measurements, established wet chemistry or other laboratory methods remain the appropriate choice. But when the same properties need to be measured repeatedly throughout the day, the time associated with sample preparation, reagents, consumables, cleaning, and operator involvement can become a significant part of the laboratory workload.
Fourier transform infrared spectroscopy (FT-IR) and Fourier transform near-infrared spectroscopy (FT-NIR) provide another option for many industrial applications.
Both techniques use infrared light to obtain information about a sample and can provide rapid analytical results. However, they operate in different regions of the infrared spectrum and are often better suited to different analytical objectives.
Understanding the practical differences between FT-IR and FT-NIR can help laboratories select the technique that best fits their QA/QC requirements.
FT-IR and FT-NIR both measure how a sample interacts with infrared radiation, but they operate in different regions of the infrared spectrum.
FT-IR laboratory instruments typically operate in the mid-infrared region. Absorption features in this region are associated primarily with fundamental molecular vibrations and can provide detailed information about the chemical bonds and functional groups present in a sample.
FT-NIR operates at shorter infrared wavelengths. Absorption in the near-infrared region is primarily associated with overtone and combination vibrations. These absorption bands tend to be broader and less individually distinct than those found in the mid-infrared region, which is one reason FT-NIR applications frequently rely on multivariate analysis and chemometric calibration models.
The relatively weaker absorption found in the near-infrared region can also make FT-NIR well suited to measurements of bulk materials, liquids, powders, pellets, and other samples where greater optical penetration can be useful.
In practice, FT-IR and FT-NIR often complement one another rather than simply competing for the same measurement.
One of the major strengths of FT-IR is the amount of molecular information available within the mid-infrared spectrum.
Because molecules and functional groups produce characteristic absorption features, an FT-IR spectrum can provide a distinctive representation of a material. This makes the technique particularly useful when identification or chemical characterization is an important part of the analytical objective.
Typical applications can include:
Sampling accessories can also allow FT-IR instruments to work with a wide range of materials, including solids, liquids, pastes, gels, and gases.
For gas applications, FT-IR can be used to evaluate composition, purity, and unknown components, depending on the analyzer configuration and measurement requirements.
FT-NIR is particularly valuable when the objective is rapid, repeatable quantitative analysis of liquids, powders, pellets, gels, hydrocarbons, polymers, and other industrial materials.
Rather than relying on a single isolated absorption feature, an FT-NIR method can use information distributed throughout the spectrum. Chemometric models are then used to establish relationships between the spectral response and results obtained from established laboratory reference methods.
Once an appropriate calibration model has been developed and validated, a single spectrum can potentially be used to determine one or several properties of a sample.
This makes FT-NIR attractive for routine measurements such as:
For hydrocarbon, chemical, polymer, and other industrial applications, FT-NIR can provide a practical way to move repetitive analytical measurements into a faster routine workflow.
A useful starting point when comparing FT-IR and FT-NIR is to ask:
What does the laboratory actually need to know about the sample?
If identification or detailed molecular characterization is the primary objective, FT-IR may be a logical technique to evaluate because the mid-infrared region provides strong, characteristic molecular absorption features.
If rapid quantitative determination of one or more material properties is the primary objective, FT-NIR may be a strong candidate, particularly when those properties can be correlated with spectral information using representative reference laboratory data.
This is not an absolute distinction.
FT-IR can be used for quantitative analysis, and FT-NIR can also support identification and classification applications. The appropriate technique depends on the sample, concentration range, measurement objective, required performance, sampling approach, and available calibration data.
The important point is that technique selection should begin with the analytical problem rather than with the instrument.
The physical characteristics of the sample also influence whether FT-IR or FT-NIR is the better choice.
Liquids, powders, pellets, gases, polymers, hydrocarbons, and other materials interact with infrared radiation differently. Sample thickness, optical pathlength, temperature, homogeneity, and presentation can all affect the resulting spectrum.
The best spectroscopy method therefore needs to consider both the property being measured and how a representative sample will be presented to the analyzer.
For a routine QA/QC application, practical questions can be just as important as the spectroscopy itself:
Answering these questions early can prevent a technically viable measurement from becoming difficult to maintain as a routine laboratory method.
Chemometrics is particularly important when evaluating FT-NIR for quantitative QA/QC.
An FT-NIR application frequently uses a calibration model to relate spectral information to results obtained using established reference laboratory methods.
Developing a useful model therefore requires representative samples that cover the expected variation in the product or process.
The quality of the reference data is equally important. The calibration model depends on the relationship between the spectral data and the reference measurements used during development.
Once a robust model has been established and validated, FT-NIR can potentially turn what previously required several separate laboratory measurements into a much faster routine analytical procedure.
This is an important consideration when evaluating the value of FT-NIR. The benefit is not simply the speed of collecting a spectrum. It is the ability to obtain useful QA/QC information repeatedly once an appropriate analytical method has been established.
Measurement speed is only one part of improving laboratory efficiency.
An analyzer that produces a result quickly but requires frequent optical alignment, replacement components, purging, or significant routine maintenance can simply move the laboratory workload from analysis to instrument upkeep.
Industrial FT-IR and FT-NIR platforms can be designed to minimize these requirements.
For example, ABB FT-IR & FT-NIR Laboratory Analyzers are designed around stable optical systems and low routine maintenance requirements for industrial laboratory applications.
ABB's MB3000 FT-IR platform uses permanently aligned optics and is designed for long-term stability, while the MB3600 FT-NIR platform is specifically designed for QA/QC analysis and method development.
For laboratories performing frequent routine testing, these characteristics can be just as important as measurement time itself.
Another consideration is where the analytical method may eventually be used.
The immediate requirement may be a faster laboratory QA/QC measurement. But once a reliable spectroscopic method has been established, there may be value in moving the measurement closer to production.
Instead of collecting a sample, transporting it to a laboratory, preparing it, performing the analysis, and communicating the result back to operations, an at-line or process analyzer can potentially provide information closer to the point where a process decision is made.
This does not mean every laboratory FT-IR or FT-NIR application should become a process measurement.
It does mean that method development in the laboratory can provide an important foundation for determining whether that transition makes sense.
Instrument-to-instrument consistency becomes particularly important in this situation. A laboratory platform that supports calibration transfer to compatible process instruments can allow a method to be developed and evaluated in a controlled laboratory environment before being considered for deployment closer to the process.
ABB specifically supports laboratory development and calibration transfer for applicable FT-IR and FT-NIR configurations. For example, ABB's MB3000-CH90 documentation states that analyzer-to-analyzer matching permits laboratory-developed calibrations to be transferred to ABB process instruments.
For applications where that transition makes sense, ABB FT-IR & FT-NIR Process Analyzers provide a path toward applying spectroscopy directly to industrial process measurements.
For organizations considering a longer-term process analytical strategy, the laboratory analyzer can therefore serve as more than a standalone QA/QC instrument. It can also provide a platform for method and calibration development.
There is no universal answer.
ABB's MB3600 FT-NIR family, for example, includes configurations for general QA/QC and method development, hydrocarbons, solids, liquid chemicals, polyols, PET, and other industrial applications.
In some laboratories, there may be applications for both technologies.
The best approach is to define the analytical objective first, understand the sample and existing reference method, and then determine which spectroscopy technique provides the most practical path to a reliable routine measurement.
A successful FT-IR or FT-NIR application is not simply about collecting a spectrum.
It requires the right combination of spectroscopy, sample handling, method development, reference data, calibration, and long-term instrument stability.
ABB's laboratory spectroscopy portfolio includes FT-IR and FT-NIR platforms for applications ranging from material identification and gas analysis to routine liquid and solid QA/QC, chemometric method development, and laboratory-to-process calibration transfer.
For industrial laboratories evaluating FT-IR and FT-NIR, the starting point should always be the application itself.
What needs to be measured? How quickly is the result required? What reference data already exists? How will samples be handled? And could the measurement eventually provide more value closer to the process?
Answering those questions can help determine not only which spectroscopy technique fits today's requirements, but also how the analytical method could evolve in the future.
Explore ABB FT-IR & FT-NIR Laboratory Analyzers
You can also explore the complete range of ABB products available from Insight Analytical or visit the ABB laboratory spectrometers portfolio for additional technical information.
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