Identification of isomers and determination of octenylsuccinate in modified starch by HPLC and mass spectrometry

A high performance liquid chromatographic (HPLC) analysis of octenylsuccinic anhydride (OSA) reagent and its bound and un-reacted forms in modified starch was developed. The HPLC system consisted of a C18 column, an elution system of acetonitrile and water containing 0.1% TFA (45:55, v/v), and a diode array detector (DAD). Using the combination of HPLC-DAD and HPLC-APCI (atmospheric pressure chemical ionisation)-MS (mass spectrometry), four main and two minor peaks were identified as 1-OS acid, cis-2-OS acid, trans-2-OS acid, 1-OSA, cis-2-OSA and trans-2-OSA, respectively. Both free and bound OS content in modified starch were successfully determined by HPLC, and direct measurement of composition of OS was achieved.