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Universal spectropolarimeter based on overtone circular dichroism measurements in the near-infrared region.

Analytical chemistry (1994-11-01)
C D Tran, V I Grishko
ABSTRACT

A novel and highly sensitive circular dichroism spectropolarimeter for the near-infrared region has been developed. In this instrument, a solid state titanium-sapphire laser that can be spectrally tuned from 670 to 1030 nm was used as the light source. The laser beam was converted into linearly polarized light by a polarizer and into left circularly polarized light and right circularly polarized light at 42 kHz by a photoelastic modulator (PEM). A limit of detection of 1.1 x 10(-6) AU was achieved by this instrument for (+)-Co(en)3(3+) at 765 nm. Further improvement including employing double modulation (at 42 kHz by the PEM and at 85 Hz by a chopper just before the laser beam was converted to CPL), demodulating and amplifying the signal with high-performance lock-in amplifiers, was made to enable the instrument to have the required sensitivity for the measurements of the circular dichroism of overtones and combination transitions of saturated chiral compounds, e.g., (R)- and (S)-camphor, (R)- and (S)-2-octanol, and (R)- and (S)-2-amino-1-octanol. Because the measured CD spectra originate from the overtones and combination transitions of the C-H and O-H groups, the spectropolarimeter can be used to detect virtually any compounds that have O-H and/or C-H groups.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
2-Octanol, 97%
Sigma-Aldrich
(S)-(+)-2-Octanol, 99%
Sigma-Aldrich
2-Octanol, ≥97%, FG
Sigma-Aldrich
(±)-2-Octanol, ≥96.0% (GC)
Sigma-Aldrich
(±)-2-Octanol, ReagentPlus®, ≥99.5% (GC)
Sigma-Aldrich
2-Amino-1-butanol, 97%