Pseudo-3D HSQC0, a method to create a true 2D HSQC0-plane. Application to softwood extract analysis

Abstract

Pseudo-3D HSQC₀ provides an alternative and easy way to record and analyze quantitative HSQC₀-data. In the original time-zero extrapolated ¹H–¹³C HSQC (HSQC₀), three separate 2D constant-time (CT) HSQC-experiments (HSQC_i, i = 1–3) are acquired, where either 1,2 or 3 consecutive CT-HSQC-propagators are repeated in each pulse sequence, and the 2D integral data from the three 2D experiments is analyzed via linear regression. In the presented pseudo-3D HSQC₀, HSQC_i is one of the dimensions and all data is contained within one dataset, which is recorded in interleaved manner by acquiring the same t₁-value for each HSQC_i-point before t₁-incrementation. The 3D-nature of the data allows the utilization of backward linear prediction to calculate an actual time-zero 2D HSQC₀ spectrum, which can be analyzed using normal 2D integration procedures for quantitative results. In all, the pseudo-3D enables straightforward, intuitive and easy analysis of the quantitative 2D HSQC₀ spectrum/plane. As the recorded pseudo 3D data contains the normal HSQC_i planes, also the classic linear regression analysis can be applied.