LC-FTIR combines liquid chromatography (LC) with Fourier transform infrared spectroscopy (FTIR) to allow for the detection and identification of separated compounds. There are two main interfaces for coupling LC to FTIR: flow cell interfaces and solvent elimination interfaces. Flow cell interfaces involve passing the LC eluent directly through an FTIR flow cell, but this approach is limited by solvent interference. Solvent elimination interfaces remove the solvent before FTIR analysis, avoiding solvent interference and allowing the full IR spectrum to be analyzed. Common solvent elimination techniques include thermospray, electrospray, and pneumatic or ultrasonic nebulization to deposit analytes on a substrate for FTIR analysis. LC-FTIR

1. LC FTIR
R.ARULKUMAR
M.PHARM PHARMACEUTICS
KMCH COLLEGE OF PHARMACY

2. Hyphenated Technologies
GC-MS LC-MS
GC-IR LC-IR
Separation
Gas Phase & Liquid Phase
Chromatography
Detection
Mass Spectroscopy Infra Red Spectroscopy DiscovIR-GC
DiscovIR-LC
Identification Data Acquisition & Analysis

3. LC - HPLC
HPLC works on the principle of the separation of the material
according to their molecular weight and polarity.

4. FTIR -Fourier Transform Infra Red
• FTIR spectroscopy deals with the quantitative measurement of the
interaction between IR radiationand materials.
• FTIR reveals molecular-vibrational transitions and provides
characteristic information on molecularstructure.

5. LC - FTIR
LCand FTIR can be combined togetherfor
the detection and identification of certain
separated compounds.
The application of FTIR spectroscopy inLC is
limited because the solvents used commonly in
LC are strong IR absobers ,
limiting both sensitivity and the spectral
information that may beobtained.

6. Features
• Online Fully Integrated System
• Fully Automated Operation: No Fractionation
• Multi-Sample Processing: 8-40 Hr ZnSe Disk Time
• Microgram Sensitivity at Sample Injection Point
• Real-Time Chromatography & Spectral Data
• Solid Phase Transmission IR Spectra: High Quality w/ Purified Analytes
• Database Search Capability & In-House Library Creation
• Data Analysis: GRAMS for Chemometrics, 3D LC-IR, Functional Group
Chromatograms & Comparisons at any Wavenumbers or across Peaks
• All LC Solvents: Water, ACN, Methanol, THF, Chloroform, HFIP
• GPC/SEC: TCB @ High Temperature (150C) HPLC: Isocratic or Gradient; Normal
& Reverse- Phase
• Compatible with LC-MS Set-Up in Parallel

7. INSTRUMENTATION

8. COUPLING OF LC-FTIR
INTERFACES
1. FLOW CELL INTERFACES
2. SOLVENT ELIMINATION INTERFACES

9. Simple and Straight forward method for the on-line coupling of
LCand FTIR.
FLOW CELL INTERFACES
MERITS
• Low cost.
• Instrumental simplicity.
• Easeof operation.
• Low maintenance.
• Possible use of non volatile buffers.
DEMERITS
• Limited choice of eluents.
• Eg :Chloroform.

10. Cell Window Materials
Ideal Characteristics :
• Chemically resistant to the eluentused.
• Withstand high pressure.
• Offer sufficient transmittance.

11. MATERIAL
Calcium
Fluoride
Germanium
Zinc
Selenide
Sodium
Chloride
Potassium
Bromide
• Expensive
• High refractive index.
• Preferred in ATR flow cells
• Cheap
• Low refractive indices minimize therisk of
spectral fringes.
• But cannot resist excessive pressure and
are strongly hygroscopic ( limits the use to
non aqueous eluents)

12. Types of Flow Cells
1. Transmission Cells
2. Cell based on Attenuated Total Reflection(ATR)
3. Cell based on Specular ReflectionMeasurements

13. Eluent
• The Mobile Phase used should not exhibit serious background
absorption. But most organic solvents used in LC show intense IR
spectra.
• To Correct the background absorption by the eluent,
background subtraction can be carriedout.

14. Correction Remedies :
ATR flow cells can be used to reduce the optical pathlength.
Post-Column extraction of the analytes from the LC effluent into a
more IR-transparentsolvent.
Deuterated solvents can be used to switch eluent- absorption bands to lower
wavenumbers and to potentially
reveal analyte absorption bands.
Increase the intensity of theIR-Source.

15. APPLICATIONS
• Analysis of samples with relatively high analyte concentrations. Eg:
Analysis of sugars in non-alcoholic beverages.
• Characterization of synthetic polymers. Eg:Polyolefins.

16. SOLVENT ELIMINATION INTERFACES
The eluent is removed prior todetection.
Eluent is directed toa nebulizer often aided
with nebulizer gas.
The Separated analytes are deposited ona
substrate.
IR Spectra from the immobilized
chromatogram may be obtained.

17. Advantages over Flow Cell FTIR
 Absence of interfering eluent absorption band - Spectral
interpretation over entire wavelength - Full exploitation of the
identification possibilities.
 Immobilized Chromatogram is still available after the
chromatographic run has been completed.
 Sensitivity can be increased by producing concentrated analyte
deposits.

18. Types of Solvent Elimination Interfaces
1. Early LC-DRIFT
2. Buffer memory
3. Spray type interfaces
a) Thermospray interface
b) Particle beam interface
c) Electrospray interface
d) Pneumonic nebulizer
e) Ultrasonic nebulizer

19. 1.Early LC-DRIFT Interfaces
The LCeluent was dripped via a heated tube into discrete
KCl-filled cups and residual solvent was removed under
a gentle stream of nitrogen before the aquisition of
spectra

20. 2.Buffer Memory Technique
• Flat KBrPlates are used for transmissionmeasurements.
• A complete chromatogram is immobilized and stored on a
substrate.
• Micro-bore LCand low flow rates were used for rapid
evaporation of eluent.
• Spectra aquistion - FTIR transmission
microscopy
• Study of analytes - X-ray Fluorescence Spectra

22. 3.Spray type Interfaces
a) Thermospray Interfaces :
– LC eluent is passed through a directly
heated vapourized tube.
– Part of the liquid evaporates to an
expanding vapour and as a result, a mist
of desolvating droplets emerges from the
end of the tube.
– Operating Temp : 100 - 300℃
– Detection limits : 1 microgram.

23. b) Electrospray interface :
• A spray of charged droplets a produced
using a highelectric field.
• The initial droplets further breakdown into
smallerdroplets as a result of solvent
evaporation and chargedensity.
• Deposit Surface - ZnSe Plate.

24. c) Pneumonic nebulizer :
 A High speed gas flow is used to distrupt the liquid surface and to form
small droplets which are dispersed by the gas.
 Deposit Surface : IR-Reflective Disc
 Gas : Nitrogen Gas.

25. d) Ultrasonic nebulizer :
 A Spray is formed by depositing the LC eflluent on a transducer that is vibrating
at ultrasonic frequencies.
 The vibrations cause the solvent to break up into small, desolvating droplets
which are transported by a carrier gas towards a substrate.
 Deposition Substrate : KBr discs

26. APPLICATIONS
i. In trace analysis.
ii. Analysis of environmental pollutants such as polycyclic aromatic hydrocarbons,
pesticides and herbicides.
iii. Analysis of Pharmaceuticals such as steroids and analgesics, and their impurities,
drug metabolites, polymeradditives, dyes, non- ionic surfactants and fullerenes.
iv. Distinction of isomers
v. Separation of secondary structure of proteins such as beta globulin and
lysozyme.
vi. A unified interface for GC, HPLC, and SFC hyphenation to FTIR applying
IR microscopic technique is also available today

27. REFERENCE
P.R.Griffiths, J.A.de Haseth, Fourier Transform Infrared
Spectrometry, Wiley, New York,1986.
G.W. Somsen et al. I.J. , Chromatography A. 856 (1999) 213 - 242
Kok, S.J.(2004), Coupling of liquid chromatographyand FTIR for
characterization of Polymers,UvA-DARE