High-throughput chiral detector and methods for using same

• US 7,301,633 B2
• Filed: 10/01/2002
• Issued: 11/27/2007
• Est. Priority Date: 10/01/2001
• Status: Expired due to Fees

• Current Assignee: Georgia Institute of Technology (University System of Georgia)
• Original Assignee: Georgia Institute of Technology (University System of Georgia)
• Inventors: Bommarius, Andreas Sebastian, Trebino, Rick P., Kimmel, Mark W., Gibbs, Phillip Ray
• Primary Examiner(s): Punnoose; Roy M.
• Application Number:
  US10/491,094
• Publication Number:
  US 20050094144A1
• Time in Patent Office: 1,883 Days
• Field of Search: 356/367, 356/369
• US Class Current: 356/369
• CPC Class Codes: G01N 21/21 Polarisation-affecting properties G01N21/19 takes precedence

Abstract

A new generation polarimetry apparatus and methodology is disclosed, which involve passing polarized light through a sample including a chiral analyte, where the analyte is under the influence of a periodically varying magnetic field. The apparatus also utilizes optical heterodyne detection and lock-in detection at higher order harmonics of the magnetic field modulation frequency to improve sensitivity and detection limits of optical properties of chiral analytes.

Claims

1. A method for detecting optical properties of an analyte in a sample comprising the steps of:

exposing a sample including a chiral analyte to a periodically varying magnetic field across a sample;

passing an incident polarized light beam having a narrow bandwidth through the sample, while the sample is under the influence of the periodically varying magnetic field to produce an output light beam, where the narrow bandwidth comprises light having a base frequency and light having a frequencies within about 1% of the base frequency and comprising less than about 1% of the light intensity;

removing substantially all of the incident polarized light from the output beam;

detecting the output beam to produce an output signal; and

lock-in amplifying the output signal, where the lock-in signal is a frequency of the periodically varying magnetic field or a harmonic thereof to produce a magnitude and phase of the output signal.

2. The method of claim 1, wherein the periodically varying magnetic field is a sinusoidally varying magnetic field.

3. The method of claim 1, wherein the narrow bandwidth comprises light having a base frequency and light having a frequencies within about 0.5% of the base frequency and comprising less than about 0.5% of the light intensity.

4. The method of claim 1, wherein the narrow bandwidth comprises light having a base frequency and light having a frequencies within about 0.1% of the base frequency and comprising less than about 0.1% of the light intensity.

5. The method of claim 1, wherein the narrow bandwidth comprises a single frequency.

6. The method of claim 1;

wherein the light is light from a laser.

7. A polarimeter method comprising the steps of:

exposing a sample including a chiral analyte to a periodically varying magnetic field across a sample;

passing an incident polarized light beam hasting a narrow bandwidth through the sample, while the sample is under the influence of the periodically varying magnetic field to produce an output light beam, where the narrow bandwidth comprises light having a base frequency and light having a frequencies within about 1% of the base frequency and comprising less than about 1% of the light intensity;

optically heterodyne detecting the output beam to produce an output signal; and

lock-in amplifying the output signal, where the lock-in frequency is a frequency of the periodically varying magnetic field or a harmonic thereof to produce a magnitude and phase of the output signal.

8. An apparatus for enhanced detection of optical properties of analytes, where the apparatus comprises:

a light source adapted to generate an incident light beam having a narrow bandwidth;

a first polarizer adapted to polarize the incident light beam to produce a polarized light beam;

a sample cell containing a sample including a chiral analyte adapted to receive the polarized beam and produce an output light beam;

a magnetic field generator surrounding the cell, and adapted to generate a periodically varying magnetic field across the cell such that the analyte is exposed to a periodically varying magnetic field as the polarized light bean passes through the cell;

a power supply adapted to supply a periodically varying electric current to the magnetic field generator to generate the periodically varying magnetic field;

a second polarizer or analyzer aligned substantially out-of-phase with the first polarizer to block substantially all of the incident polarized light to form an analyzed, output light beam;

a detector adapted to receive the analyzed output light beam and produce an output signal; and

a lock-in amplifier adapted to amplify the output signal and generates an amplitude and phase of the output signal, where the lock-in frequency is the frequency of the periodically varying magnetic field or a harmonic thereof.

9. The apparatus of claim 8, further comprising a modulator adapted to modulate the polarization of the polarized beam prior to being received by the sample cell.

10. The apparatus of claim 8, wherein the lock-in amplifiers is locked to a combined frequency comprising frequency of the power supply and the frequency of the modulator.

11. An apparatus for enhanced detection of optical properties of analytes, where the apparatus comprises:

a light source adapted to generate an incident beam of light having a narrow bandwidth;

a first polarizer adapted to polarize the incident light beam to produce a polarized light beam;

a flow cell into which a sample including a chiral analyte is supplied, where the cell is adapted to receive the polarized beam and produce an output beam;

a magnetic field generator surrounding the cell and adapted to generate a periodically varying magnetic field across the cell such that the analyte is exposed to a periodically varying magnetic field as the polarized light beam passes through the cell;

a power supply adapted to supply a periodically varying electric current to the magnetic field generator to generate the periodically varying magnetic field;

a second polarizer or analyzer aligned substantially out-of-phase with the first polarizer to block substantially all of the incident polarized light to form an analyzed, output light beam;

a detector adapted to receive the analyzed output light beam and produce an output signal; and

a lock-in amplifier adapted to amplify the output signal and generates an amplitude and phase of the output signal, where the lock-in frequency is the frequency of the periodically varying magnetic field or a harmonic thereof.

12. The apparatus of claim 11, further including a sample delivery system for supplying a sample to the flow cell.

13. The apparatus of claim 12, wherein the sample delivery system is an analytical separation apparatus or a sampling apparatus.

14. The apparatus of claim 11, further comprising a modulator adapted to modulate the polarization of the polarized beam prior to being received by the sample cell.

15. The apparatus of claim 14, wherein the lock-in amplifiers is locked to a combined frequency comprising frequency of the power supply and the frequency of the modulator.

16. The apparatus of claim 11, wherein the light source produces right and left handed circularly polarized light and where the apparatus further includes a handedness modulator that periodically changes the handedness of the light so that a circular dichroism of the analyte can be measured.

17. An apparatus for enhanced detection of optical properties of analytes, where the apparatus comprises:

a first light delivery system including a light source adapted to generate light having a narrow bandwidth and a plurality of optical fibers, each fiber adapted to carry a beam of incident light;

a first polarizer adapted to polarize the incident light beams to produce polarized light beams;

a sample cell including a plurality of sample chamber, each chamber containing a sample including a chiral analyte and each chamber adapted to receive a polarized light beam and produce an output light beam;

a magnetic field generator surrounding the cell and adapted to generate a periodically varying magnetic field across each chanter of the cell such that the analytes in the chambers are exposed to a periodically varying magnetic field as the polarized tight beam passes through the cell;

a power supply adapted to supply a periodically varying electric current to the magnetic field generator to generate the periodically varying magnetic field;

a second light delivery system including a plurality of optical fibers, each fiber adapted to receive one of the output light beams and a second polarizer or analyzer aligned substantially out-of-phase with the first polarizer to block substantially all of the incident polarized light in each output light beam to form analyzed, output light beams;

a detector adapted to receive the analyzed output light beams and produce output signals; and

a lock-in amplifier adapted to amplify the output signals and generate an amplitude and phase of each output signal, where the lock-in frequency is the frequency of periodically varying magnetic field or a harmonic thereof.

18. The apparatus of claim 17, further comprising a modulator adapted to modulate the polarization of the polarized beam prior to being received by the sample cell.

19. The apparatus of claim 18, wherein the lock-in amplifiers is locked to a combined frequency comprising frequency of the power supply and the frequency of the modulator.