Detection, isolation, and identification of impurities in technical thiofanox

Abstract

The detection, isolation, and identification of the impurities in the technical grade of the insecticide thiofanox are described. A 13C NMR method was employed to detect impurities at about the 0.1% level or greater. The 13C spectrum of very high signal-to-noise ratio of an impurity concentrate was used to guide subsequent separation and identification work. The sensitivity and reliability of this approach are discussed. Preparative and semipreparative high performance liquid chromatography was employed to isolate 39 nonvolatile components. These were identified on the basis of spectral data and by comparisons with authentic samples which were synthesized when necessary. Some stereochemical assignments are made on the basis of NMR chemical shifts. An additional 30 volatile components were isolated and identified by vacuum distillation and gas chromatography/ mass spectrometry.

Significance of impurities in the safety evaluation of crop protection products (IUPAC Technical Report)

“…GC/MS alone cannot usually be used for identification of unknown substances [51]. In many cases, 1 H, 13 C, 31 P NMR [28,34,45], and other spectroscopic methods have been successfully applied for the identification of unknown impurities.…”