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How does the IRmadillo differ to conventional FTIR?

Fourier transform infrared (FTIR) technology is based on an arrangement of mirrors to split light into two separate paths and then recombine them to create an interference pattern of light (called an “interferogram”). This pattern is fed into the Fourier transform algorithm producing a spectrum that can be interpreted and analysed.

With conventional FTIR design, this is achieved using a pair of mirrors, where one is static and the other moves along a smooth and well-defined track. This means conventional FTIR instruments can be very sensitive to vibration and movement, as even small vibrations can cause noise or artefacts to appear in spectra as the moving mirror is affected. Manufacturers have managed to reduce the impact of vibration by novel mirror designs, but not completely remove the susceptibility. This means that conventional FTIR instruments can be installed in laboratories or other benign environments, but are often not suitable for industrial installations.

The addition of HeNe lasers into these interferometers as an internal reference have made substantial changes to some aspects of precision, but they do not resolve the weakness to vibration, nor do they affect long-term measurements. In fact, conventional instruments tend to show poor long-term stability, and need re-baselining (called a background or reference scan) fairly frequently. This makes them suitable for short-term reactions and single batches, but can be challenging to use for long-term or continuous manufacturing campaigns.

What about fibres? I’ve heard those mean I can install the instrument far away?

Although some instruments are installed in benign environments using solid “light pipes” directly onto the process of interest, the vast majority of FTIR installations use fibre-optic probes. They are intended to be used to create distance between the instrument and the process (the source of vibration); in reality the average length is about 5 m, so they still require the instrument to be installed relatively near the process. These fibres can give more flexibility on where the instrument can be installed but have a number of drawbacks:

  • They can be very fragile and easy to break: the fibres themselves are thin and delicate, and can easily be accidentally broken – especially in an industrial environment
  • They can be very expensive to manufacture: this means that the cost to install and replace them is very high, potentially adding a higher ongoing cost to instrument ownership if they need repairing or replacing
  • They can have very low spectral throughput: which means that the signal in the instrument is very low. This can be partially overcome by installing very sensitive detectors (which often need liquid nitrogen or Stirling engine cooling – another potential point of failure) or a high-powered infrared source (which have shorter lifetimes than lower powered ones)

When would we use a conventional FTIR?

The potential weakness of traditional fibre-based FTIR systems on a manufacturing floor are part of their greatest strength in the laboratory. The flexible fibres are easy to introduce into smaller reaction vessels for experimental characterisation and scale-down experiments, which typically have short reaction times so the need to take frequent reference scans with conventional FTIR is not a problem in the laboratory. An example application for conventional FTIR is:

  • Laboratory process characterisation: performing experiments in purpose-built reaction systems that include FTIR and other tools (such as calorimetry and temperature logging, off-gas analysis); or reactions on extremely small scales that require purpose-built glassware with very small fibre probes.

When would we recommend choosing IRmadillo?

The IRmadillo is ideal for use in industrial and manufacturing settings because of its enhanced stability and vibration resistance. Some reasons you may consider the IRmadillo over conventional FTIR are:

  • You operate continuous or long-term manufacturing campaigns: if your process runs over multiple days, weeks or months then you need a solution that is reliable and stable. This is where the IRmadillo’s novel design with static mirrors and low-powered infrared source offer long-term stability and reliability – it’s a solution you can trust.
  • Your environment is dirty, hazardous, and not suitable for fragile instruments: the IRmadillo has hazardous area certification, meaning you can install it directly into hazardous areas with no additional protection required. It has IP65 rating, making it waterproof and resilient to dirt, hosing down and adverse weather conditions.
  • You want an instrument that is easy to install: the single light pipe probe mounted directly onto a small instrument body makes the IRmadillo remarkably easy to install. In most cases no sample conditioning is required, and the probe can be directly into the process pipework or a small sample loop if you’d like easy access for cleaning.
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