Nuclear magnetic resonance spectroscopy. Concentration dependence of the T₁ relaxation time for ¹³C in dioxane-D₂O. Some experimental problems with T₁ measurements

The ¹³C T₁ relaxation times determined for dioxane-D₂O solutions by the progressive saturation method have been found to range from 5 sec for 1:1 (v/v) dioxane-D₂O to 12 sec for neat dioxane. The concentration dependence roughly parallels the inverse of the viscosity and is likely to be associated with changes in correlation times because of hydrogen bonding. A 2:1 (v/v) dioxane-D₂O mixture with a T₁ of 6.2 ± 0.6 sec at 30°C has been found to be a useful standard for checking instrument performance in the determination of T₁ values. A number of experimental problems associated with measuring T₁ are discussed.