scope:

General

This Standard describes a method for the quantification of the aliphatic (R-OH), carboxylic acid (R-COOH), and phenolic (Ph-OH) hydroxyl groups present in lignin. Phenolic hydroxyl groups include

a) syringyl (S), guaiacyl (G), and p-hydroxyphenyl (H) units; and

b) condensed phenolics incorporating β-5, 4-O-5', and 5-5' inter-unit linkages.

Methodology

The procedure utilizes derivatization with a phosphorus-containing reagent followed by ³¹P NMR analysis.

Application

The procedure is applicable to dry solid lignins (e.g., in powdered form), isolated from the pulping processes in their acid form, that are completely soluble in the NMR solvent mixture. If the lignin is not fully dissolved in the NMR solvent, the data obtained will represent only the structure of the soluble portion of the lignin sample.

Exclusions

The procedure does not apply to raw black liquor, wet lignin, or lignin with a high ash or carbohydrate content, to the extent that these affect lignin solubility in the selected solvent system.

Terminology

In this Standard, "shall" is used to express a requirement, i.e., a provision that the user is obliged to satisfy in order to comply with the standard; "should" is used to express a recommendation or that which is advised but not required; and "may" is used to express an option or that which is permissible within the limits of the Standard.

Notes accompanying clauses do not include requirements or alternative requirements; the purpose of a note accompanying a clause is to separate from the text explanatory or informative material.

Notes to tables and figures are considered part of the table or figure and may be written as requirements.

Annexes are designated normative (mandatory) or informative (non-mandatory) to define their application.