Carboxymethyl starch sodium is the most commonly used superdisintegrant, and the degree of substitution and crosslinking density are the important quality attributes that affect its water swellability and disintegration performance. By exploring the correlation between degree of substitution, crosslinking density, and water swellability, this study aims to provide a theoretical reference for the production of disintegrant with excellent performance.

Seventeen batches of carboxymethyl starch sodium were collected. Low-field nuclear magnetic resonance technique was used to determine the crosslink density values. And the degree of substitution and water swellability value were determined by physical-chemical method. The correlation between crosslinking density, degree of substitution and water swellability was investigated by Pearson correlation.

There were significant differences in the attribute values of products from different sources. The crosslinking density was significantly negatively correlated with the degree of substitution and water swellability, and the correlation coefficients were -0.814 and -0.854. The degree of substitution was significantly positively correlated with the water swellability, and the correlation coefficient was 0.823.

The crosslinking density and the degree of substitution are the critical quality attributes that affect the disintegration of carboxymethyl starch sodium. Understanding the disintegration behavior of disintegrants is of great significance for the development of pharmaceutical solid preparations. Clarifying the relationship between the disintegration characteristics of carboxymethyl starch sodium and crosslinking density and degree of substitution will help to select the correct disintegrant for a given formulation.