Quantitative Analysis of Chemically Modified Starches by 1H-NMR Spectroscopy

A quantitative 1H-NMR method for the determination of the Molar Substitution (MS) of acetylated and hydroxypropylated starches was developed and tested for MS ranging from 0.09 to 0.5. Results were checked using the Johnson method and a titration method for hydroxypropylated and acetylated starch, respectively. Hydroxypropylated starch was produced using both a static mixer reactor (SMX type) and a co-rotating twin screw extruder. Acetylated starch was produced using a counter-rotating twin screw extruder. Quantitative analysis results of the 1H-NMR method were in good agreement with traditional analysis methods for all samples tested. Main advantage of the 1H-NMR method is the considerable time saving as compared to the traditional analysis methods.