ASTM F2259-10(2012)e1
Standard Test Method for Determining the Chemical Composition and Sequence in Alginate by Proton Nuclear Magnetic Resonance (¹H NMR) Spectroscopy

Standard No.

ASTM F2259-10(2012)e1

Release Date

2010

Published By

American Society for Testing and Materials (ASTM)

Latest

ASTM F2259-10(2012)e1

Scope

Significance and UseTop Bottom

4.1 The composition and sequential structure of alginate determines the functionality of alginate in an application. For instance, the gelling properties of an alginate are highly dependent upon the monomer composition and sequential structure of the polymer. Gel strength will depend upon the guluronic acid content (F_G) and also the average number of consecutive guluronate moieties in G-block structures (N_Ggt;1).

4.2 Chemical composition and sequential structure of alginate can be determined by ¹H- and ¹³C-nuclear magnetic resonance spectroscopy (NMR). A general description of NMR can be found in lt;761gt; of the USP 35-NF30 . The NMR methodology and assignments are based on data published by Grasdalen et al. (1979, 1981, 1983).^{4, 5, 6} The NMR technique has made it possible to determine the monad frequencies F_M (fraction of mannuronate units) and F_G (fraction of guluronate units), the four nearest neighboring (diad) frequencies F_GG, F_MG, F_GM, F_MM, and the eight next nearest neighboring (triad) frequencies F_GGG, F_GGM, F_MGG, F_MGM, F_MMM, F_MMG, F_GMM, F_GMG. Knowledge of these frequencies enables number averages of block lengths to be calculated. N_G is the number average length of G-blocks, and N_Ggt;1 is the number average length of G-blocks from which singlets (-MGM-) have been excluded. Similarly, N_M is the number average length of M-blocks, and N_Mgt;1 is the number average length of M-blocks from which singlets (-GMG-) have been excluded. ¹³C NMR must be used to determine the M-centered triads and N_Mgt;1. This test method describes only the ¹H NMR analysis of alginate. Alginate can be well characterized by determining F_G and N_Ggt;1.

4.3 In order to obtain well-resolved NMR spectra, it is necessary to reduce the viscosity and increase the mobility of the molecules by depolymerization of alginate to a degree of poly......

ASTM F2259-10(2012)e1 history

• 2010 ASTM F2259-10(2012)e1 Standard Test Method for Determining the Chemical Composition and Sequence in Alginate by Proton Nuclear Magnetic Resonance (¹H NMR) Spectroscopy
• 2010 ASTM F2259-10 Standard Test Method for Determining the Chemical Composition and Sequence in Alginate by Proton Nuclear Magnetic Resonance (¹H NMR) Spectroscopy
• 2008 ASTM F2259-03(2008) Standard Test Method for Determining the Chemical Composition and Sequence in Alginate by Proton Nuclear Magnetic Resonance (¹H NMR) Spectroscopy
• 2003 ASTM F2259-03 Standard Test Method for Determining the Chemical Composition and Sequence in Alginate by Proton Nuclear Magnetic Resonance (¹H NMR) Spectroscopy