Cloud point preconcentration and capillary electrophoresis. Monitoring the elimination of gadolinium-based pharmaceuticals

ORTEGA, CLAUDIA; SILVA MARÍA F.; GOMEZ, MARÍA ROXANA; OLSINA, ROBERTO; MARTINEZ, LUIS DANTE

Simposio; 7mo Simposio Latinoamericano en Aplicaciones de la Electroforesis Capilar y Tecnología del Microchip en Biotecnología, Biomedicina, Biofarmacia e Industria, (LACE 2001); 2001

The use of NMR contrast agents is an active area of research. Specific extraneous resonating nuclei can be introduced to label particular parts of a molecule. Physical chemical and biological results support the use of strongly chelated Gd complexes as NMR contrast agents. A rapid and complete excretion of the contrast agent is desired when a diagnostic examination of a patient is being carried out. [Gd(DPTA)]2- and [Gd(DOTA)]2- are rapidly excreted mainly into urine, while free Gd(III) is retained, with liver being the main repository . The excretion half-life of free Gd is enormously different from that of the Gd complexes: 7 days versus 5 minutes, respectively. Free Gd(III) ion has very poor acute tolerance and its long-term tolerance is unknown. It is therefore very important to determine free Gd(III) content in a Gd-based pharmaceutical. Analytical analysis are thus necessary to determine with confidence whether or not Gd was injected as [Gd(L)] , or together with unchelated Gd(III), and if it was completely eliminated. The use of micellar solutions in different areas of analytical chemistry has attracted much attention in recent years. Among other micelle-based separation methods, the cloud point extraction is an efficient extractive step for the enrichment of rare earth elements (REE), allowing the quantification of such metals at ppb levels. In the present work we have developped and optimized a high sensitive, simple and low-cost method for the preconcentration and determination of total and free Gd(III) contents in urine in order to monitoring the elimination of the metal after the injection of gadolinium-based pharmaceuticals. After the CPE preconcentration step, the surfactant-rich phase was analized by CE. The effect of several experimental parameters affecting the coupled methodology have been evaluated and optimized. Optimun results were obtained with a 50 mM sodium tetraborate, pH 9.22, with 30% acetonitrile. The carrier electrolyte gave baseline separation with good resolution, reasonably migration times, great reproducibility and accuracy.