Characterization of dextrin hydrogels by FTIR spectroscopy and solid state NMR spectroscopy

Abstract

Fourier transform infrared (FTIR) and 13 C solid state nuclear magnetic resonance (NMR) spectroscopy were used to study dextrin structural changes occurring upon hydrogel formation by vinyl acrylate (VA) grafting and subsequent free radical polymerization. The degrees of VA substitution (DS) and polymerization (DP) were quantified up to 40%VA by FTIR intensity measurements and partial least squares (PLS)/FTIR, the latter being a faster and less error-prone method. Above 40%VA, both parameters are underestimated by FTIR. A spin counting NMR experiment showed high carbon observabilities for hydrogels and improved PLS/NMR models were achieved for DS and DP determination. Alternative NMR integration methods are hindered by the broad VA peaks and need for area correction, due to their CP dynamics. NMR changes in C1 profile showed that a single helical conformation predominates at lower %VA, being replaced by disordered conformations as %VA increases. Furthermore, a correlation FTIR/NMR study indicated that ring conformations are significantly affected in hydrogels, compared to unpolymerized dextrin.

Two-dimensional correlation spectroscopy — Biannual survey 2007–2009

“…Chae et al [124] used IR-UV hetero-spectral correlation for the study of photo-induced segmental reorientation of photosensitive polyester as a function of UV irradiation exposure energy. IR-NMR hetero-spectral correlation of dextran hydrogel made by enzymatic grafting of vinyl acrylate with varying degree of substitution was reported by Garcia et al [125]. New band assignment was made by comparing IR and NMR spectra.…”

“…Zhang et al [104] studied insect venom by covariance 2D NMR. Garcia et al [125] studied dextran hydrogel made by enzymatic grafting of vinyl acrylate with varying degree of substitution. Carmona et al [271] reported the 2D IR study based on H/D exchange reaction for analyzing hepatitis C viral RNA sequence.…”

“…Šašić [68] applied generalized 2D correlation to NMR and noted some difficulty specifically associated with handling NMR data. Garcia et al [125] carried out hetero-correlation between IR and NMR spectroscopy. Ruan et al [237,238] applied generalized 2D correlation to the NMR study of the conformational changes of silk fibroin.…”

“…The in vitro formation of advanced glycation end-products in type I collagen after Fe 2+ -catalyzed non-enzymatic glycocylation was studied by 2D IR, where different Fe 2+ catalyst dose was used as the perturbation variable. Garcia et al [125] used chemical structure differences for 2D correlation analysis. Dextran hydrogel made by enzymatic grafting of vinyl acrylate with varying degree of substitution was studied.…”

Homo- and Hetero-Covariance NMR Spectroscopy and Applications to Process Analytical Technology

“…Prominent examples comprise generalized indirect covariance and multidimensional covariance NMR as well as the combination of covariance and non-uniform sampling of data [54][55][56][57]. While the concept of homo-and hetero-covariance spectroscopy was developed nearly three decades ago, there are relatively few reports on the use of synchronous and asynchronous spectra involving NMR spectroscopy [3,14,55,58,59]. In contrast, an abundant number of investigations have applied so-called statistical hetero-spectroscopy (STOCSY) that has delivered important contributions to the field of metabolomics and whose variants have recently been depicted like a phylogenetic tree [22,32,60].…”