Gas chromatographic determination of poly(3-hydroxybutyrate) with alkaline hydrolysis and acid esterification

A new pretreatment method for the gas chromatographic determination of poly(3-hydroxybutyrate) (PHB) was developed based on a combination of alkaline hydrolysis and acid esterification. The determination principle is as follows: PHB is hydrolyzed to its monomer 3-hydroxybutyrate by alkaline solution, followed by the esterification with methanol to generate the methyl ester of 3-hydroxybutyrate catalyzed by acid, which is detected by a gas chromatography. From the comparison of effects of alkali and acid on PHB hydrolysis and 3-hydroxybutyrate esterification, alkali resulted in a better performance for the hydrolysis, while acid was better for the esterification. The pretreatment conditions for PHB were optimized and the determination performance was characterized.