Development of an online citrate/Ca2+ sensing system for dialysis

Abstract

An online citrate and Ca²⁺ sensing system based on sequential injection analysis (SIA) is developed as a safety module for hemodialysis. Host 1 displays high affinity towards citrate, and was selected for this study owing to its unique structural features. The o-aminomethylphenylboronic moiety can effectively interact with the α-hydroxycarboxylate moiety of citrate and the remaining two guanidiniums may further stabilize the complex viahydrogen bonds. Fura-2 chelates to Ca²⁺ with a high selectivity and affinity and was utilized in this study for Ca²⁺ measurements. The citrate sensing chemistry via an indicator displacement assay is orthogonal to the Ca²⁺ sensing chemistry, and the use of sophisticated chemometrics is not required for data analysis. The citrate and Ca²⁺ concentrations in dialysate samples are measured with the developed SIA system. The obtained citrate concentrations were verified via a commercially available enzymatic assay and an NMR method, respectively, while the Ca²⁺ concentrations were verified via atomic absorption.