How does the IRmadillo differ to Off-line Analysis?
The IRmadillo is based on FTIR spectroscopy, which is either on-line (with a recirculation loop) or in-line (being installed directly into the process pipework or reaction vessel) gives a continuous measurement updating frequently. This can be used for process control and feedback algorithms, as there is no delay between making a measurement and receiving the result.
Off-line analysis is an extractive technique which involves taking a sample from the process and then performing the actual measurement either in a laboratory (for true off-line analysis) or using an instrument nearby (for at-line analysis). There are numerous different types of off-line and at-line measurement that can be made. A selection of them is:
- HPLC: high performance liquid chromatography is a technique for separating out different components from a mixture (the “chromatography” part of the name) which are then detected using a separate detector. This technology requires calibration standards to be run through the instrument regularly to ensure that the process has not drifted, and requires a special “method” for each and every chemical to be measured. This is often run as a true off-line analysis technique as HPLC instruments need clean and benign environments – such as laboratories.
- GC-MS: gas chromatography mass spectrometry involves running a sample through a column that separates out the chemicals within the mixture, and then detects them using a mass spectrometer. This is an effective method for gaseous samples or volatile processes that can be evaporated easily but is completely ineffective for processes with high boiling points. There are systems designed to automatically take samples and measure them at-line.
- ICP-AES: inductively coupled plasma atomic emission spectroscopy is a technique that burns a sample in a controlled environment and measures the light that is emitted. This is a powerful method of measuring very low levels of inorganic molecules and metal ions (such as Ca2+ or Mg2+). The technology does require standards, and a benign environment similarly to HPLC.
- Chemical assays: the vast majority of classical chemical assay techniques have been replaced by instrumentation, but some processes do still require wet chemical workup. Chemical titrations are still commonly used, for example to analyse the free fatty acid content in edible oil refining or to measure the levels of dissolved SO2 in sulphate/sulphite mixtures.
There are lots of other off-line instruments that may used in laboratory settings (for example plate readers in biochemical settings, or NMR instruments in organic synthesis laboratories), but for process control the above techniques cover the majority of approaches.
What is the benefit of the IRmadillo over off-line analysis?
There are a number of benefits to using an on-line analytical tool such as the IRmadillo over off-line and extractive techniques. These are:
- Safety: taking samples off-line of processes that may be very hot, under high pressure, corrosive, explosive or highly toxic is never a safe activity to perform. By removing the need to take samples off-line the IRmadillo can dramatically reduce the hazards involved with analysing a process.
- Time to measurement: the IRmadillo is constantly measuring the process it is installed in, with a default update frequency of 2 minutes. This means there is never a delay in measurement, and problems can be spotted quickly and rectified before causing large scale issues or failed batches.
- Less error prone: the IRmadillo uses an internal calibration that is stable and requires no further input on a day to day basis. Off-line analysis normally requires dilution and active laboratory work, which can be prone to error – especially during night shifts. The IRmadillo completely removes this risk.
- Real-time control: the IRmadillo can be connected directly to a DCS, SCADA or PLC system, enabling the measurements to be used as an input into control algorithms, controlling chemical dosing, temperature settings or other control valves. This means that the process can be constantly optimised, 24 hours a day, 7 days a week.
- More representative: some processes have short lived or reactive chemicals present inside them, that may disappear in the delay to off-line analysis. The IRmadillo directly observes these chemicals and registers their presence. This can be very important for qualitative measurements where the instrument is registering whether a process is in or out of specification rather than a direct chemical concentration measurement. Moreover, off-line analysis will change the pressure and temperature of a process, which can cause analysis to be offset against the conditions within the process.
What would we use off-line or extractive sampling for?
Off-line laboratory testing plays an important role in both process characterisation and calibration of online instrumentation. Some examples of where we would use it are:
- Where the process or problem is completely unknown: characterisation of unknown processes and problems should involve a wide range of different instrumentation and processes, to fully characterise the various chemicals present. NMR, laboratory FTIR and mass spectrometry (i.e. time of flight spectrometry) can all be used for structural elucidation. X-ray fluorescence and ICP-AES might detect inorganic contaminants, whilst scanning electron microscopy might identify a particular solid contaminant such as a piece of equipment that has degraded and contaminated a process.
- Where on-line instruments require calibration: almost all on-line instrumentation requires calibration of some form, and technologies such as HPLC are commonly used to achieve this. It should be remembered that HPLC instruments have their own error associated with their use and cannot be considered 100% accurate, but when some form of reference data is required they are often a good choice.
- For final QC checks: many regulators and quality assurance teams require a final off-line analysis before allowing a product to be released for sale. In these cases a highly controlled laboratory instrument operating to GMP standards is often used.
What would we recommend choosing the IRmadillo over off-line and extractive sampling for?
While off-line analysis can often give very accurate and precise readings, its use in real-world manufacturing and industrial processes can be limited. Here are some examples where we believe the IRmadillo is the more useful instrument to use:
- Where real-time control is required: off-line samples cannot be processed rapidly to enable real-time control, so an on-line analyser such as the IRmadillo is required to obtain continuous data that be used to make adjustments to the process.
- Where the process is hazardous: if the very action of taking a sample off-line could cause injury or damage equipment then an on-line solution is the only realistic approach.
- Where the analysis is complicated: complicated analytical processes are prone to error, and for industrial processes errors can cost money – the built in calibration of the IRmadillo removes this problem, enabling cost saving and efficiency improvements.