Quantitation of Trace Components in Mixtures Utilizing Selective Pulse NMR Spectroscopy, Applications toward Automated Analysis

Nuclear Magnetic Resonance (NMR) spectroscopy is well suited for quantitative analyses of complex chemical mixtures. 1D ¹H NMR typically provides the highest sensitivity with excellent linear response to component concentrations. Quantitation of key trace analytes in the presence of very strong signals from the bulk matrix can however be problematic or even impossible, depending on concentration, using typical broad band excitation. This is due to dynamic range limitations of the analog to digital converter (ADC). These limitations can be overcome by the use of band selective shaped pulses to excite only the region containing the minor analytes while excluding the regions containing strong matrix signals which would exceed the ADC range. Region selective 1D ¹H NMR methods for direct quantitation of µg/g aldehyde concentrations in olive oil and honey matrices without the need for extraction or concentration of analytes will be discussed. Implementation of these methods into automated analysis methods will also be presented.