Development of Novel Absolute Determination Methods for Chiral Organic Compounds and Lithium

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1. A novel absolute determination method using chirality without any calibration curves or comparison standards has been proposed for phosphorus-containing amino acid-type herbicides, glufosinate (D,L-GLUF). This method is based on a change in the enantiomeric ratio after the spiking of a known amount of the enantiomers with different enantiomeric ratios to a sample. D,L-GLUF was determined by adding a known amount of L-GLUF to the sample, derivatizing them with dansyl chloride, and measuring the ratio of the peak area of the D-isomer to that of the L-isomer by means of γ-cyclodextrin modified capillary zone electrophoresis with UV detection. The accuracy and precision of the method were evaluated using a synthetic sample. The mean values obtained for D- and L-GLUF agreed with the values taken within 1.6% ; also the reproducibility was as good as less than 2.8%. Furthermore, fluorescence detection and large-volume sample stacking for the capillary electrophoresis were studied to resolve and detect trace D,L-GLUF in femto-mole levels.2. A novel analytical method, substoichiometric isotope dilution nuclear magnetic resonance analysis (SID-NMR), has been proposed. The present method consists of the complexation of Li^+ with a substoichiometric amount of cryptand [2.1.1] (C211) and the subsequent signal intensity measurement of an isotope of ^7Li by ^7Li-NMR. The resonance signal (chemical shift) of the Li(C211)^+ complex was completely separated from that of free Li^+ in the NMR spectrum and the integrated area of the signal from a constant amount of the Li(C211)^+ complex was substoichiometrically measured. The reproducibility of the integrated area was 2.1% as relative standard deviation for (4.1-8.2) × 10^<-3> mol dm^<-3> Li when a Li-β-diketone complex was used as an external standard. The validity and the usefulness of SID-NMR were demonstrated by the determination of Li in a synthetic solution.