Analysis of Human Serum Urea Using Ion Exchange Chromatography

Abstract

In uremia, toxins such as urea accumulate in the blood and therefore need to be removed. The effectiveness and efficiency of removal can be assessed accurately by determining the concentration of uremic toxins in the blood. For that purpose a selective analytical method is required. Current techniques for analysis of urea used in clinical practice include the ionselective methods is conversion of urea to ammonium with urease and then determination of ammonium (ionselective electrode method), coloring ammonium with reagents (Indophenol method), or automatic analysis predominantly based on colorimetry. Another method is determination of absorbance at 340 nm of NADH from NAD combined with a transaminase. These methods all have the problem of not being able to differentiate urea from endogenous ammonia. Furthermore in current clinical tests, differential analysis of free and bound urea is not possible. It is essential to selectively determine the free urea. In order to do this ion-exchange chromatography has been shown to be the most appropriate for differentiating urea from endogenous ammonium and separating it from other components in the serum. Selective free urea analysis can be attained by ultrafiltration.