Light Source: Globar Silicon Carbide Rod (5mm diameter, 50 mm long) Heated electrically to 1300 – 1500 K Positive temperature coefficient of resistance Electrical contact must be water cooled to prevent arcing Ingle and Crouch, Spectrochemical Analysis

Sample Preparation for IR Spectroscopy Ingle and Crouch, Spectrochemical Analysis

Liquid Samples: Cell Thickness Ingle and Crouch, Spectrochemical Analysis

Window and Cell Materials Ingle and Crouch, Spectrochemical Analysis

Solvents Pretsch/Buhlmann/Affolter/Badertscher, Structure Determination of Organic Compounds

Suspension Media for Solid Samples Pretsch/Buhlmann/Affolter/Badertscher, Structure Determination of Organic Compounds

Interferences Pretsch/Buhlmann/Affolter/ Badertscher, Structure Determination of Organic Compounds

Fourier Transform IR Spectrometer Ingle and Crouch, Spectrochemical Analysis

Michelson Interferometer Split source into two beams whose path lengths can be varied periodically to give interference patterns.

Michelson Interferometer

Interferograms Douglas A. Skoog and James J. Leary, Principles of Instrumental Analysis, Saunders College Publishing, Fort Worth, 1992.

Fourier Transform of the Interferogram Gives the Spectrum Ingle and Crouch, Spectrochemical Analysis

Resolution: Jacquinot’s Advantage: Resolution is not limited by aperture width. Can increase light throughput by fold. Multiplex Advantage (aka Fellget’s Advantage): Signal from all are continuously monitored, increasing S/N. S/N for average of n measurements: Advantages of FT-IR over Dispersive IR

How long would it take to capture a dispersive IR spectrum from 500 – 5000 cm -1 with 3 cm -1 resolution elements if you could scan one resolution element every 0.5 seconds? If you want to increase your S/N by a factor of 2, how long will you have to scan? If you collect FT-IR for the same length of time, what is the theoretical S/N advantage? Are you getting the concept?

Evanescent Waves for TIR Microscopy Increased → Increased d p

ATR-FTIR Spectroscopy (Attenuated Total Reflection FTIR) Ingle and Crouch, Spectrochemical Analysis ZnSe or Ge

Schematic of a FTIR Imaging Spectrometer Koenig, J.L.; Wang, S.-Q.; Bhargava, R., Anal. Chem. 2001, 73, 361A.

Focal Plane Array Colarussa, P. et al. Appl. Spectroscopy. 1998, 52, 106A. Square array of MCT pixels Indium electrical contact between each MCT contact and readout electronics layer Total area ~ 1 mm 2 Total time < 10 sec

IR Array Detectors Colarussa, P. et al. Appl. Spectroscopy. 1998, 52, 106A.

FTIR Imaging: Dissolution of a Polymer (a) Two materials are brought into contact and allowed to diffuse across the interface. The diffusion region develops over time. (b) An image is obtained by monitoring radiation passing through the sample at a direction perpendicular to the diffusion direction. (c) Concentration profiles for three different functional groups obtained from the same sample as in (b) (diffusion of a liquid crystal monomer at 265 K for 3 h). Koenig, J.L.; Wang, S.-Q.; Bhargava, R., Anal. Chem. 2001, 73, 361A.

FTIR Imaging: Dissolution of a Polymer FTIR images of the dissolution of poly(alpha-methylstyrene) with a mole weight of 31,000 as a function of time with a mixture of the good solvent methyl isobutyl ketone and the nonsolvent (C 6 D 12 ). Koenig, J.L.; Wang, S.-Q.; Bhargava, R., Anal. Chem. 2001, 73, 361A.

FTIR Microspectroscopy: Tissue Imaging Colarussa, P. et al. Appl. Spectroscopy. 1998, 52, 106A.

FTIR Microspectroscopy: Tissue Imaging Colarussa, P. et al. Appl. Spectroscopy. 1998, 52, 106A.

Other Uses for IR Array Detectors Colarussa, P. et al. Appl. Spectroscopy. 1998, 52, 106A.

Other Uses for IR Array Detectors Colarussa, P. et al. Appl. Spectroscopy 1998, 52, 106A.