Tools and strategies for processing diffusion-ordered 2D NMR spectroscopy (DOSY) of a broad, featureless resonance: an application to methylaluminoxane (MAO)

• Published in: Analytical and bioanalytical chemistry 2004-03, Vol.378 (6), p.1574-1578
• Main Authors: Eilertsen, Jan Lasse, Hall, Randall W, Simeral, Larry S, Butler, Leslie G
• Format: Article
• Language: English
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-003-2457-1

DOSY has been extremely successful in many studies of molecular weight distributions, especially when the components are separable along the chemical shift axis. However, an unresolved NMR resonance yields the familiar problem of overlapping exponential decays. In a study of methylaluminoxane (MAO), a set of data processing and simulation tools were developed: read Bruker data files (Matlab); preliminary non-linear least-squares fit with f-test (Matlab); movie generation of the fits (Matlab); conversion of diffusion coefficients to molecular masses through molecular volumes (Gaussian-98); and simulation of DOSY data sets for various molecular mass distributions (Mathematica). These tools are presented here and briefly compared with other DOSY analysis methods. Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00216-003-2457-1. The following Matlab and Mathematica files are made available: Plot_Raw_DOSY.m, Fit_Two_Component.m (which calls One_Gaussian_LEASTSQ.m, Two_Gaussian_LEASTSQ.m, and pFTest.m), and DOSY_theory.nb. Note: Matlab v5.2 optimization toolbox, as supplied, lacked a confidence interval subroutine; upon our request, confint.m was provided to the authors by Mathworks, Inc. Newer versions of Matlab have a similar program already included in the optimization.