Separation of catechol derivatives by capillary electrophoresis using a polyvinylpyrrolidone solution

A poly(N-vinylpyrrolidone) (PVP) solution was used as a running buffer solution of capillary electrophoresis (CE) for the separation of catechol derivatives. No improvement in the separation efficiency between the cationic catechol derivatives, such as dopamine and epinephrine, was observed when a phosphate buffer solution containing PVP was used as the running buffer. This may have been due to a weak interaction of the cationic catechol derivatives with PVP. On the other hand, the separation efficiency between anionic catechol derivatives, such as caffeic acid, DOPAC including ascorbic acid, was greatly improved by the addition of PVP to the phosphate buffer solution, compared with the buffer solution without PVP. The improvement in the separation efficiency was due to the difference in the interaction of the solutes with PVP. The mobility of the anionic solutes in the presence of PVP, which was calculated from the migration times of the solutes and a neutral marker, increased in the order caffeic acid <DOPAC< ascorbic acid. This sequence suggests that the interaction of the solutes with PVP is larger in the order ascorbic acid <DOPAC< caffeic acid. The formation constants of the PVP complex with the solutes were estimated from the relationship between the PVP concentration in the running buffer and the mobility of the solutes obtained in this work.