“Infrared” is the electro-magnetic radiation region between0.7µm to 1000µm (Doyle), for chemicalanalysis, between 2.5 µm and 25 µm will receive the best results. mid-IR regionis where the most functional groups organic molecules’ frequencies lie, so quantitativecalibration can be done very straightforwardly and it is robust, spuriousartifacts effects will less likely to arise. Figure 1: Electromagnetic Spectrum The nature of black body radiation has led to the radiation sourcepower available in the mid IR is a lot lower, mid-IR detectors have a lowersensitivity when operating in room temperature compare to near-IR counterparts.These two factors are the main reasons why less sensitive dispersive approach isnot used in the near-IR, and Fourier transform infrared (FTIR) approach is usedinstead.
During sample interfacing, absorptions in the mid-IR relate to thefundamental molecular vibrations are orders of magnitude stronger than the nearIR overtones, mid-IR will not be able to use simple transmission cells as hownear-IR liquid analysis is carried out.In Situ FTIR is the Fourier Transform Infrared Spectroscopy,it has been growing in popularity since its introduction, it is becomingcommonly used in pharmaceutical industry to determine the chemistry in achemical. Whenever there is a new chemical entity that needs to enter thecommercial production, the chemical process and the chemistry behind it must bethoroughly understand in order to have a safe, robust and reliable productionto prevent any consequential reaction occur to human body. The ReactIR in situFourier Transform Infrared answer all the questions in a chemical reaction, itgives the time it starts, the time it stops, the expected mechanism for thereaction and its kinetics.
ReactIR in situ Fourier Transform Infrared (FTIR)Spectroscopy provide real time monitoring of all the key reaction species, italso shows the changes in the reaction throughout the progression, the ReactIRAttenuated Total Reflection (ATR) provide the specific information from the reactioninitiation, conversion, intermediates and endpoint, this will allow a muchbetter understanding of the mechanism in the reaction compare to the oldmethods.FTIR Spectroscopy is carried out in situ. In traditionmethod, in order to find out the chemical reaction mechanism, kinetics,conversion etc, chemicals have to be taken out from the reaction and undergoesvaries analytical techniques, these chemical could be very toxic, hightemperature or high pressure, which means it is not always easy to undertakethese analytical techniques, this shows the significances of FTIR Spectroscopycarried out in situ, the probe isinserted directly into the reaction mixture, so reaction sample will not changeduring sampling, and it is much more safe to carry the reaction. (MettlerToledoAC)