Determination of citrate released from stabilized gold nanoparticles by capillary zone electrophoresis

In this article, we report a pilot study on release of citrate ions from citrate-stabilized gold nanoparticles by capillary zone electrophoresis. First, a method for determination of citrate released from nanoparticles was developed using 5 mM phthalate buffer pH 6.5 with polybrene capillary inner wall coating. Within these conditions, citrate migrated in 1.8 min and it can be determined with LOD of 7 µmol/L using molybdate as the internal standard. The release of citrate was initiated by addition of common MOPS buffer ions used in capillary electrophoresis to nanoparticles samples. Non-linear behavior was found that proves release of citrate from stabilized gold nanoparticles. The release is initiated when 5 mM MOPS is added to nanoparticles’ solution. This behavior can partially explain zeta potential change of the nanoparticles from –34 mV in bulk solution to –28 mV in 50 mM MOPS.