Routine Creatinine Determination: An Equilibrium Technique Involving Reusable Cation Exchange Membranes

Abstract

A specific creatinine method is described. Serum samples of 400 μ1 are diluted with hydrochloric acid. At a pH of approx. 3, positively charged creatininium ions are isolated from other Jaffé-chromogens by adsorption to cation-exchange resin membranes fixed to polystyrene rods. After adsorption the resin membranes are washed with distilled water, and bound creatinine is released into tubes containing alkaline picrate. Finally, the resin membranes are regenerated using lithium chloride solution. The membranes can be used through several hundreds of cycles. In routine conditions the day-today coefficient of variation has been estimated to be 4.4%. Reference values: males 70–125 μmol/l, females 50–105 μmol/l.

Key Words:

• Adsorption
• creatininium ions
• ion-exchange membrane