a. Near-infrared – 4,000 to 14,000 cm-1b. Mid-infrared – 670 to 4,000 cm-1c. Far- infrared – less than 670 cm-11. Gas in an evacuated cylinderThe spectrum of a low-boiling liquid or gas can be obtained by permitting the sample to expand into an evacuated cylindrical cell equipped with suitable windows.2. SolutionsWhen feasible, a convenient way of obtaining infrared spectra is onsolutions prepared to contain a known concentration of sample, as is generally done in ultraviolet/visible spectroscopy.3. Dissolved in solventsThere is no particular solvent that is completely transparent in the entire mid-infrared region. Therefore solvents are chose on the basis of the region the sample will absorb.4. Liquid in cellBecause of the tendency for solents to absorb, infrared cells are ordinarily much narrower than those employed in the UV/Vis regions. Fixed path length cells can be filled or emptied with a hypodermic syringe.5. PelletsOne of the most popular techniques for handling solid samples has been KBr pelleting. In using this technique, a milligram or less of the finely ground sample is ultimately mixed with about 100 mg of dried potassium bromide powder.6. MullsMulls are formed by grinding 2 to 5 mg of the finely powdered sample in the presence of one or two drops of a heavy hydrocarbon oil. If hydrocarbon bands are likely to interfere, fluorolube, a halogenated polymer can be used instead.CHE 331Chapter 17 Applications of Infrared Spectrometry Modern infrared spectrometry is a versatile tool that is applied to the qualitative and quantitative determination of molecular species of all types. The applications of infrared spectrometry can be split into three main areas:a. Near-infrared – 4,000 to 14,000 cm-1b. Mid-infrared – 670 to 4,000 cm-1c. Far- infrared – less than 670 cm-1 Spectral Regions Type Measurement Type Analysis Type SamplesNear-infrared Diffuse ReflectanceAbsorptionQuantitativeQuantitativeSolid, LiquidGaseous MixturesMid-infrared Absorption ReflectanceEmissionQualitativeQuantitativeChromatographicQualitativeQuantitativeSolid, liquid, gasSolid, liquid, gasSolid, liquid, gasPure solid or liquidAtmospheric sampleFar-infrared Absorption Qualitative Pure inorganic or metal organic Types Of Samples1. Gas in an evacuated cylinderThe spectrum of a low-boiling liquid or gas can be obtained by permitting the sample to expand into an evacuated cylindrical cell equipped with suitable windows.2. SolutionsWhen feasible, a convenient way of obtaining infrared spectra is onsolutions prepared to contain a known concentration of sample, as is generally done in ultraviolet/visible spectroscopy.3. Dissolved in solventsThere is no particular solvent that is completely transparent in the entire mid-infrared region. Therefore solvents are chose on the basis of the region the sample will absorb.4. Liquid in cellBecause of the tendency for solents to absorb, infrared cells are ordinarily much narrower than those employed in the UV/Vis regions. Fixed path length cells can be filled or emptied with a hypodermic syringe.5. PelletsOne of the most popular techniques for handling solid samples has been KBr pelleting. In using this technique, a milligram or less of the finely ground sample is ultimately mixed with about 100 mg of dried potassium bromide powder.6. MullsMulls are formed by grinding 2 to 5 mg of the finely powdered sample in the presence of one or two drops of a heavy hydrocarbon oil. If hydrocarbon bands are likely to interfere, fluorolube, a halogenated polymer can be used instead.Mid-Infrared Absorption SpectrometryMid-infrared absorption and reflection spectrometry are major tools for determining the structure of organic and biochemical species. Qualitative AnalysisThe mid-infrared region is further broken down into the group frequency region(1,280 to 5,000 cm-1) and the fingerprint region (670 to 1,280 cm-1).Quantitative ApplicationsQuantitative infrared absorption methods differ somewhat from UV/VIS molecular spectroscopic methods because of the greater complexity of the spectra, the narrowness of the absorption bands, and the instrumental limitations of infrared instruments. Quantitative data obtained with dispersive infrared instruments are generally poorer in quality to data obtained with UV/VIS spectrophotometers. References:Chem Center - Powered by ACShttp://www.chemcenter/orgScience