Simultaneous Quantification of H2O2 and Organic Hydroperoxides by 1H NMR Spectroscopy

:due to similar reactivity of organic hydroperoxides (OHPs), anHPLC separation step is typically required for their indirect (chemical)quantification in mixtures. The high sensitivity of chemical shifts to chemicalstructure makes NMR an ideal tool for the simultaneous quantification of OHPs inmixtures, but the concentration of these analytes in the samples of interest is usuallywell below the sensitivity of standard NMR experiments. This sensitivity problemcan be mitigated by taking advantage of the fact that thezmagnetization of theH2O2resonance recovers at the rate of hydrogen exchange with water, which issignificantly faster than longitudinal relaxation, thus enabling very fast scanning forsignal-to-noise enhancement. An adaptation of theE-BURP2pulse is described thatsuppresses the water signal by more than 4 orders of magnitude, yielding uniformexcitation of peroxide signals without interference of the ca. 108-fold stronger H2Oresonance. We demonstrate the method for a mixture of OHPs and report thechemical shifts for multiple OHPs that are of interest in atmospheric chemistry. Asshown for hydroxymethyl hydroperoxide, the chemical decay of OHPs can be tracked directly by NMR spectroscopy

Automated summary

Due to the similar reactivity of organic hydroperoxides (OHPs), HPLC separation is typically required for their indirect quantification in mixtures. NMR is an ideal tool for simultaneous quantification of OHPs in mixtures due to its high sensitivity to chemical shifts, but the concentration of these analytes in the samples of interest is usually below the sensitivity of standard NMR experiments.