FLOW-INJECTION ANALYSIS WITH HIGH-SENSITIVITY OPTICAL-ROTATION DETECTION

The construction and characterization of a flow injection analysis sys tem with high-sensitivity, laser-based (488 nm), optical rotation dete ction (FIA-OR) is described. Baseline noise is reduced to similar to 1 0 mu deg by addition of a pressure pulsation damper between the pump a nd the autosampler. Sensitivity is increased 100-fold compared to a hi gh-quality conventional polarimeter, and detection of a 43-ng sample o f sucrose (25-mu deg rotation) is demonstrated. The instrument respons e is linear over a 500-fold range of concentration to 21 mu g of sucro se injected, with the upper limit set by laser beam distortion caused by sample refractive index effects. Specific rotation values at 488 nm for 11 organic molecules are measured by FIA-OR with good precision a nd agree with values obtained by a conventional polarimeter. FIA-OR an alysis of enantiomeric purity of (1S,2R)-(+)-ephedrine is found to be more discriminating than conventional polarimetry for the analysis of solutions with high enantiomeric excess.