Light Source: GlobarSilicon 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

2

nb

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

Ingle and Crouch, Spectrochemical Analysis

Michelson Interferometer

Split source into two beamswhose path lengths can bevaried periodically to giveinterference patterns.

Michelson Interferometer

http://www.newport.com/Introduction-to-FT-IR-Spectroscopy/405840/1033/catalog.aspx

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: mx

1

Jacquinot’s Advantage: Resolution is not limited by aperture width. Can increase light throughput by 10-200 fold.

Multiplex Advantage (aka Fellget’s Advantage): Signal from all l are continuously monitored, increasing S/N.

S/N for average of n measurements:

Advantages of FT-IR over Dispersive IR

xNn

N

S xS

How long would it take to capture a dispersive IR spectrumfrom 500 – 5000 cm-1 with 3 cm-1 resolution elements if youcould scan one resolution element every 0.5 seconds? If youwant to increase your S/N by a factor of 2, how long will youhave 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

http://www.olympusmicro.com/primer/java/tirf/penetration/index.html

2

12

322

0

sin2 cf

p

nnd

Increased l → Increased dp

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 contactbetween each MCT contactand readout electronics layer

Total area ~ 1 mm2

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 (C6D12).

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.