HPLC Separation of Cyclen Polycarboxylates Using Contactless Conductivity Detection

Abstract

Polycarboxylate derivatives of cyclen are potential La(III) ion carriers for application in medicine, e.g. in magnetic resonance imaging (MRI). The compounds are prepared in multistep syntheses and hence the development of efficient separation and analytical methods for the determination of purity of the products and intermediates is desirable. This work was focused on HPLC methods suitable for the purpose. Out of the four modified stationary phases, only the pentafluorophenylpropyl modification, offering mix-mode interactions, was found suitable. The effect of the mobile phase composition was investigated using aqueous methanol, acetonitrile and buffers of different pH. The best results were obtained with a methanol-water mixture (85:15, v/v). UV detection is unsuitable for the purpose because of its low absorption coefficients, even at short wavelengths. A new type of contactless conductivity detector provided a better sensitivity than the UV detector.