IR spectroscopy and in particular mid-IR region provides a wealth of information on chemical composition of materials. Sampling techniques and HATR accessory in particular have contributed immensely to the scope of applications. Developments in fibre optics and their adaptation as probes for spectroscopic analysis has further extended the scope of FTIR applications.
Fibre-optic probes help do away with complicated and time-consuming sample preparation practices for liquids and solids. Probes serve the dual purpose of a detection system using sophisticated ATR technique and as a wave guiding fibre. This level of flexibility coupled with the ability to sample from difficult and in accessible points such as reaction flasks or reaction vessels makes fiber optic probes a powerful sampling tool.
The probes are capable of use under ambient conditions of temperature and pressure as well as extremes would as technological advances protect the device from environmental stresses. Highly aggressive chemicals such as fuming acids may not affect the fiber but can attack ATR crystals or epoxy used to hold the crystals to the fibre. Under such conditions diamond crystal can replace materials like ZnSe. Tailor made probes can withstand temperatures in the range of -1000C to +180°C and pressures up to 500 bar.
Fibre – optic probes in addition to laboratory reaction monitoring have found a number of applications in process monitoring and product control and also in control of quality of incoming raw materials. Some typical applications are:
Foods – alcoholic beverages, real-time fermentation monitoring in bioreactors, vegetable oil production, etc
Polymers – degree of polymerization and curing, cis-trans conversions, studies of coatings on metal surfaces,etc.
Pharmaceuticals – pharmaceutical residues on reactor surfaces and cleaning validation
Human skin studies – lipid composition of different skin layers, contamination of skin from environmental exposure or contact with chemicals
The fibre optic probe has been accepted as validated sampling tool and today many industries are handing over such routine analysis to partially trained manpower. It can be truly said that fibre-optic probes are extension arms of spectroscopic analysis as they offer sampling solutions outside the spectrometer sample compartment and even under extreme conditions of temperature and pressure.