Enhanced selectivity and detectability in absorption and fluorescence methods based on polarization modulation [Thesis]
- Ames Laboratory (AMES), Ames, IA (United States); Iowa State Univ., Ames, IA (United States)
Polarization properties of light can be exploited to develop more selective spectroscopic methods of chemical analysis. Modulation of polarization coupled with lock-in detection provides a powerful detection scheme with improved detectabilities. This dissertation demonstrates the importance of optical design in systems utilizing polarization modulation. In Chapter 2, optimization of modulation frequency and efficiency and simplification of optical design led to a 10-fold improvement in the detectability for sodium atoms by laser polarization spectroscopy. The limit of detection for sodium atoms by this method is 2 ng/l. The increased S/N at 150 kHz allowed operation in the dispersion mode and subsequently provided linear calibration curves. Chapters 3 and 4 present the first studies of fluorescence-detected circular dichroism (FDCD) for on-column detection in capillary electrophoresis (CE). Detection by direct fluorescence (FL) is carried out simultaneously and provides a convenient means of evaluating the FDCD performance. Modulation efficiency and balance and preservation desired polarization are discussed in detail and are shown to have great influence on the selectivity attainable by FDCD. Among techniques that sense optical activity, FDCD provides superior detectability on an absolute scale because it is suitable for picoliter detection volumes. Optical activity signals were observed for riboflavin (LOD = 0.2 fmol) and for less than 50 fmol of some fluorescein isothiocyanate-amino acid derivatives (FTC-amino acids) by FDCD/FL-CE. The major chapters have been indexed separately for inclusion on the data base.
- Research Organization:
- Ames Laboratory (AMES), Ames, IA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 6113692
- Report Number(s):
- IS-T--1449; ON: DE91008926
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400102* -- Chemical & Spectral Procedures
ABSTRACTS
ALKALI METALS
AMINO ACIDS
ANTITHYROID DRUGS
BEAMS
CARBONIC ACID DERIVATIVES
CARBOXYLIC ACIDS
CHEMICAL ANALYSIS
DATA ACQUISITION SYSTEMS
DICHROISM
DOCUMENT TYPES
DRUGS
ELECTROMAGNETIC RADIATION
ELECTROPHORESIS
ELEMENTS
EMISSION SPECTROSCOPY
EQUIPMENT
EXTRACTION APPARATUSES
EXTRACTION COLUMNS
FLUORESCENCE SPECTROSCOPY
HORMONE ANTAGONISTS
LASER SPECTROSCOPY
LEADING ABSTRACT
METALS
MODULATION
OPTICAL EQUIPMENT
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PERFORMANCE
POLARIZATION
POLARIZED BEAMS
RADIATIONS
REAGENTS
RIBOFLAVIN
SENSITIVITY
SEPARATION EQUIPMENT
SODIUM
SPECTROSCOPY
TECHNOLOGY ASSESSMENT
THIOCYANATES
VISIBLE RADIATION
VITAMIN B GROUP
VITAMINS