title: Direct quantification of M/G ratio from (13)C CP-MAS NMR spectra of alginate powders by multivariate curve resolution.
abstract: Multivariate curve resolution (MCR) was applied to (13)C cross-polarisation (CP) magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of non-depolymerised alginate powders obtained from brown seaweed plus a pure mannuronate sample isolated from Pseudomonas fluorescens for estimation of the mannuronic acid/guluronic acid ratio (M/G ratio). An excellent MCR model with a correlation coefficient of r(2)=0.99 was established between the estimated M/G ratios and the M/G ratios obtained from the traditional (1)H solution state NMR method. The new method allows for successful determination of the M/G ratio independent of the calcium content (at least up to 2.4%, which was the upper limit in this study) with a root mean square error of prediction of 0.05. It is thus concluded that (13)C CP-MAS NMR in combination with multivariate curve resolution is a reliable, convenient (no sample preparation is required) and relatively rapid method for M/G ratio determinations of alginates and it may serve as a good alternative to the chemical techniques traditionally used.
authors.affiliation: University of Copenhagen, Department of Food Science, Quality & Technology, Frederiksberg C, Denmark. tisa@life.ku.dk
authors.forename: Tina
authors.initials: T
authors.lastname: Salomonsen
authors.forename: Henrik Max
authors.initials: HM
authors.lastname: Jensen
authors.forename: Flemming Hofmann
authors.initials: FH
authors.lastname: Larsen
authors.forename: Stefan
authors.initials: S
authors.lastname: Steuernagel
authors.forename: Søren Balling
authors.initials: SB
authors.lastname: Engelsen
mesh_terms: D000464:Alginates / Q000737:chemistry; D020723:Glucuronic Acid / Q000737:chemistry; D006603:Hexuronic Acids / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D015394:Molecular Structure
chemical_list: D000464:Alginates; D006603:Hexuronic Acids; D020723:Glucuronic Acid