Finding the right fit: FT vs Dispersive NIR

The longest continuously running mountain biking series in the United States is hosted in southwest Pennsylvania. Every year, hundreds of locals show up to test themselves in the 5-race series and vie for the title of “local hero.”

Races each take place at different venues, and each venue has a signature “wrench” to throw at riders, ranging from long, strenuous climbs to short but incredibly steep kickers, jagged rock gardens, jostling roots and log jumps, hair-raising descents, and (sometimes) even some smooth, flowing singletrack.

So what’s the point and how does this have anything to do with NIR?

The series champs are the best all-around riders. Top riders are often the most physically fit, yes, but they also are the most prepared. Oftentimes, they have to bring different bikes to best-match the terrain of any given race to get an extra advantage. They bring their fat-tired bike to glide over the rock gardens, or their narrow-tired, lightweight bike to pull away from the competition in the cyclocross race on the dry, grassy field. They bring their full-suspension bike to the downhill race, and their favorite geared bike to the climbing course.

The point is… the equipment (i.e. bike, NIR technology) you bring to the table should best meet the challenge (i.e. race course, NIR application) to perform at the best possible level and achieve the best possible result.

BUCHI offers four different NIR products, the NIRFlex N-500, NIRMaster, ProxiMate and NIR-Online, to meet different challenges or needs, including: application flexibility or difficulty, sampling location, sampling speed, or equipment ruggedness. To meet those requirements with the best advantage, BUCHI NIR products are engineered using one of two technologies: Fourier-transform (FT) and dispersive NIR.

FT-NIR

An FT-NIR, or Fourier Transform NIR, uses an interferometer to modulate the NIR signal and a computer to obtain the spectra of materials.

The simplest form of an interferometer is the classical Michelson, which consists of a beamsplitter and two mutually perpendicular plane mirrors–one which remains static and one which moves. The beamsplitter reflects part of the NIR energy from the source (typically a halogen bulb) onto each mirror. The reflected beams are recombined at the beamsplitter and directed out. When the distance between the beamsplitter and the two mirrors is equidistant, the two beams interfere constructively. The interference between the beams with an optical path difference (i.e. as the moving mirror is displaced) creates an interferogram. The mathematical treatment called Fourier transform is used to convert the interferogram to a spectrum.

Advantages of FT-NIR polarization inteferometer:

  • Simultaneous measurement of all wavenumbers and greater light throughput, giving an improved signal-to-noise ratio
  • High wavelength resolution, leading to good data transferability (i.e. calibration transfer) and improved selectivity for spectral features with narrow bandwidth
  • Single-beam interferometer without typical double-beam divergence for mechanically and temperature stable beam alignment*
  • More robust design than standard Michelson interferometer*

Because there are fewer optical components to attenuate radiation, more power reaches the detector, providing the benefit of better signal-to-noise ratio. Because the resolution at discrete wavelengths is much better, elements which interact within very narrow bands can be detected (i.e. better selectivity).

* The additional benefits of insensitivity to vibration and robustness are realized with the BUCHI polization interferometer used in both the N-500 and NIRMaster products. This benefit in rough environments is attributed to the difference of spatial movements and the optical path shifts for the two light beams in a birefringent crystal of variable thickness. Whereas in a Michelson type interferometer mechanical distortions directly affect the interference, such effects are reduced by a factor of 10 to 20 in a crystal interferometer.  

In addition to displaying the performance benefits of FT-technology, the BUCHI NIRFlex-N500 product is a good fit for an R&D setting or lab where the sample types are varied (e.g. liquids and solids). The N-500 has hot-swappable sampling modules (e.g. fiber optics, solids and liquid measurement cells) and sampling add-ons (e.g. petri dish holders and 6-position vial carousels) to optimize method performance across a variety of applications.

The BUCHI NIRMaster blends the performance of FT-technology with the more rugged demands of at-line installation points. The NIRMaster is the world’s first dedicated FT-NIR standalone spectrometer available in food-grade PMMA or stainless steel. The accuracy and reproducible performance of polarization FT technology plus the hygienic design with certified dust protection (IP64 or IP65) meets the easy cleaning processes requested for at-line machinery.

As mentioned previously, the optical bench for the N-500 and NIRMaster are the same. While the N-500 isn’t suitable for at-line work due to the risk of ingress, both products have a similar robustness to mechanical disturbances.

However, when an application doesn’t require the level of spectroscopic performance delivered by FT to deliver acceptable property measurement accuracy, or when ultra-fast measurement speed or online measurements are required, then users should look to dispersive NIR technology.

Dispersive NIR

In a dispersive NIR system, light is constantly emitted from an NIR source (typically a tungsten halogen lamp) onto a sample. The diffusely reflected light from the sample is directed to a dispersive element (e.g. stationary grating) and the resulting spatially distributed monochromatic light is detected. In lieu of a moving monochromator and a single detector, a diode array may be used. A diode array usually consists of 256 diodes, each of which collects the intensity of a certain wavelength range depending on its spatial position.  These individual diode signals are commonly referred to as pixels. Division of measured intensity (I) by intensity of a white reference spectrum (I0) as well as conversion of pixels to a wavelength scale results in a so-called spectrum, I/I0 plotted against nm or cm-1.

advantages of dispersive technology

  • Measurement speed
  • Ruggedness

Utilizing diode arrays gives rise to detecting a specified wavelength range in milliseconds. Averaging up to 200 spectra per second improves signal-to-noise ratio and allows detection of fast moving products in pipes or on conveyor belts. Because diode array based process analyzers do not contain any moving parts, they are robust by design, making them suitable for rough industrial conditions such as vibrations, extreme temperatures or humidity.

Example non-contact sensing of powder moving along a conveyor belt using NIR-Online.

In a process environment diode array process analyzers are desirable over scanning or interferometer based technologies. Rotating wavelength filter wheels or Fourier Transform (FT) spectrometers with moving parts require longer measuring times and the quality of measured data relies on stable measurement conditions.

The BUCHI NIR portfolio offers two products using diode array technology: the NIR-Online process analyzer and the standalone at-line ProxiMate NIR.

The ProxiMate was born out of a call for a lower-cost and higher IP-rated at-line solution for food and feed applications. The IP-69 designation of the ProxiMate indicates complete protection against dust particle up to 4 microns in size and protection from water projected from a powerful nozzle in any direction. The instrument can be washed down in exactly the same way as other plant machinery.

Like the NIR-Online, the ProxiMate delivers fast measurements, enabling greater throughput and less downtime in the lab or on the plant floor. Because the optical bench of the NIR-Online and ProxiMate is identical, data and calibration transfer could also provide faster method transfer from at-line to on-line applications or vice-versa.

Making your selection

Here are some additional factors to consider when it comes to finding that “perfect fit:”

Spectroscopic performance – as dictated by the application. Some applications require higher spectral resolution FT to observe small peak shifts or narrow bandwidth features, while the desired accuracy for other measurements can be easily obtained with a dispersive diode array system.

Sampling considerations (i.e. type(s), frequency, volume, location). If an R&D lab needs to optimize sampling for liquids, solids and slurries, then having the flexibility of a laboratory instrument, plus the benefits of optimal spectral resolution, would lead the user to an FT-NIR like the NIRFlex N-500. When sampling volume and/or frequency requirements are moderate, sample variation is low (i.e. you don’t need to optimize measurement conditions for drastically different materials like slurries, clear liquids and powdered solids) and measurements are more practically done on the plant floor, then an ingress protected NIR solution is advantageous. When sampling points are potentially hazardous or impractical, or when an ideal sampling frequency is very high or continuous, then an in- or online NIR product that is integrated into the processing equipment is clearly the better fit.

Cost and payback. In general, the cost of a diode array instrument is less than an FT-NIR product. Payback can be determined based on the frequency or cost of wet chemistry methods, the reduced sampling time of the NIR method over alternative methods, or mitigating the risk of a failed or recalled batch or accepting out of spec raw materials. Moreover, if an application exists as an out-of-the-box solution (e.g. a “pre-calibration” for moisture, protein and fat in ground meat) then the cost of method development will decrease sharply.

Certifications & standards. Consider whether the installation points or application requires food-grade materials, explosion-proof design, GMP or non-GMP software before making a decision. For example, the BUCHI NIRMaster, ProxiMate and NIROnline products are considered safe in food environments. The BUCHI NIRFlex N-500 and NIRWare software package offers 21 CFR Part 11 compliance and IQ/OQ, whereas the other products do not. The BUCHI NIR-Online® ExProof process analyzer is constantly over-pressurized, eliminating the risk of flammable gas penetration.

Summary

Just as a mountain bike race would best handled on a mountain bike… there are well-suited NIR products to handle specific application and workplace requirements. Need some more help getting matched up? Contact us.

Supporting References

Skoog, D. A., F. J. Holler, and T. A. Nieman. 1998. Principles of Instrumental Analysis, 5th ed. Chicago, Ill.: Harcourt Brace College Publishers

Burns, D.A., Ciurczak, E.W. 2007. Handbook of Near-Infrared Analysis, 3rd ed. CRC Press.

BUCHI Product Pages

NIRSolutions Product Page

NIR-Online Product Page

Quality is Going to the Dogs.

Don’t worry, it’s a good thing.

This week, BUCHI Product and Application Specialists mingled with pet food suppliers and manufacturers at the Petfood Forum 2019 in Kansas City, MO. Some key topics on deck for event speakers include nutrition, labeling, product development, safety and manufacturing.

BUCHI Laboratory Solutions can help keep the fur kids happy and healthy.

Did you know BUCHI has its paws in the formulation, quality control and labeling aspects of the pet food industry?

Formulation

Our spray dryer and freeze dryer equipment can be used to develop innovative, nutritious and shelf-stable products for happy, healthy pets. These technologies have been used to optimize stability and bioavailability for pet food ingredients, including: natural products, amino acids, proteins, vitamins and oils.

Quality Control

WATT Global Media conducted a survey and identified raw material ingredient quality as the top concern among surveyed Petfood Forum registrants. BUCHI provides expertise and laboratory and process equipment which helps to address quality standards at various stages along the pet food value chain, from raw material intake, to in-process quality control, to finished product testing to validate label claims.

The multi-axis plot shown below is a type of decision tree to determine which is the most appropriate method to select for protein determination, comparing Kjeldahl (red line), Dumas (yellow dashed line) and NIR (blue dashed line). For example, if your current need is for a high-speed analysis with a small environmental footprint, suitable for moderate sample type variation, then NIR is a good choice. If labeling compliance is of chief concern, with potential to adapt methods to broad variation in sample types, then Kjeldahl is a better selection.

Raw material inspection is an important component of a quality control program. Understanding the actual quality and parameters of incoming materials can help avoid process or nutritional deviations that occur because of out-of-spec ingredients. There is also an economical component: formulate closer to target and minimize issues like “protein give-away,” or avoid product recalls due to mislabeled or contaminated ingredients.

Near-infrared spectroscopy is one tool in the analytical toolbox that has been useful for establishing quality in raw ingredients, from grains to raw meats. The speed of analysis is well-suited for a quick quality check against Certificates of Analysis upon receipt of supplied goods.

Typical parameters measured by NIR in meat products include: protein, fat and moisture. For meat applications, color, pH, salt, starch and collagen content may also be implemented. These and other calibrations may be further refined with the addition of samples representative of the ingredient suppliers used within any production scheme.

Click to view a webinar highlighting ways to manage pet food production & quality using NIR

Properties of raw meat ingredients can be monitored at the time of their production, with installation points over a conveyor belt, directly in product pipes or processing equipment including deboners, grinders or mixers. An example of online measurements of protein, moisture and fat content of minced meat at a mixer has been described in a BUCHI short note . These same calibrations can be applied in-line or off-line for the pet food manufacturer who sources meat from a supplier. Large premium meat producers such as Mircana have successfully implemented this equipment to make real-time corrections to processing deviations at the mixer.

Watch this short clip to see how single or multipoint inline NIR sensors can help you control your production process

Labeling

Kjeldahl is the most established reference method for protein determination in feed, and commonly serves as a reference for NIR. You can find applications for protein and fat determination by Kjeldahl and Soxhlet extraction using our BUCHI Application Finder. Some of the content you’ll find includes:

The BUCHI Booth at Petfood Forum is getting packed up later today. If you missed us, Contact Us to schedule a chat with an Application Specialist, or even a virtual demo!

Evolution of BUCHI NIR

February 12 was Darwin Day. Darwin, of course, was known for his theories of evolution. While his theories continue to be hotly debated 137 years after his passing, none could argue that products and companies must evolve in some capacity to keep pace with, and meet the demands of customers-at-large.

Charles-Darwin-1880-631

Borrowing the words of Spanish soccer player Gerard Pique, “Evolution is all about looking forward.” The BUCHI NIR portfolio shows evidence of evolution in that sense. 

The BUCHI NIR “big bang” occurred in 1999 with the acquisition of Buhler NIR, with incremental steps leading up to the dramatic upgrade to the NIRFlex series, and so far culminating with the N-500 FT-NIR product.

N-500_Solids_left_312093-1104

The NIRFlex bench-top instrumentation was designed to meet consumer demands in both R&D and routine testing labs for true flexibility and high performance. Hot-swap modules accommodate nearly any sample type (i.e. solid, liquid, semi-solid or slurry), while the Fourier-transform (FT) technology provides exceptional precision. A novel single-beam FT design further propels instrument performance, stability and robustness, while hardware and software components continue to meet even the demands of the  pharmaceutical regulatory agencies.

NIRMaster_NIRMaster_ProNext, the NIRMaster was added to the portfolio specifically to serve the demands of the food and feed industries, bringing with it IP-54 and IP-65 ingress protection and features designed to ensure food safety. This revolutionary design was the first to marry the accuracy of FT-NIR with a robust and hygienic standalone at-line design suited for the production floor.

NIR-Online

In 2005, the BUCHI portfolio expanded with the acquisition of German on-line sensor manufacturer NIR-Online, just a modest train ride away from company headquarters in Flawil, Switzerland. With this acquisition, BUCHI was finally able to offer a true in- and on-line NIR solution for process control. Since its introduction, the NIR-Online product has further evolved, expanding capabilities to include multiplexing, and continuing to meet requirements for workplace safety, including explosion-proof options for hazardous environments.

In late 2018, the BUCHI NIR portfolio saw its next evolution: the ProxiMate. This at-line workhorse took the speed and agility of the NIR-Online solution at-line, creating an affordable option for the typical food and feed industry customer without compromise in quality or performance.

ProxiMate_masterProxiMate offers 3 main benefits for food and feed industry users: applicative fit, extreme robustness and simple operation.

  • BUCHI application chemists have developed many ready-to-use pre-calibrations typically required by the food and feed industries, enabling accurate results with minimal effort and by users of any ability level

Of course, the idea of the “survival of the fittest” comes to mind on Darwin Day. It seems that the more recent of our evolutionary steps in the NIR product portfolio has been hyper-focused on robustness–survival in the dirtiest, harshest, or most hazardous environments. Learn more about ProxiMate and join us on this Extreme Journey along the NIR evolutionary path!