A Nuclear Double Resonance Spectrograph has been designed and constructed with emphasis on quadrupolar nuclei of half-integral spins. The use of a data acquisition and processing system featuring the A/D converter, signal averager with built in fast Fourier transformation hardware greatly improves the S/N ratio. The spectrograph has been used to detect certain organochlorine, carbamate and symmetrical triazine pesticides. Concentration levels that can be detected range from 15 to 100 micrograms per liter. Since the measurements are done below ice temperatures, heat-labile compounds can be detected without conversion to more suitable derivatives as in gas chromatography. Fats and oils in sample extracts do not interfere with the measurements. Further improvement in sensitivity is possible by using liquid nitrogen-cooled, ferrite-cored electromagnet, by increasing the polarizing field and by reducing receiver recovery time.
In addition to analysis of pesticides, the Nuclear Double Resonance technique can be used to study the electronic structure of molecules
