Measurement of sodium ion concentration in undiluted urine with cation-selective polymeric membrane electrodes after the removal of interfering compounds

Abstract

The measurement of sodium ion concentration in urine can provide diagnostic information and guide therapy. Unfortunately, neutral-carrier-based ion-selective electrodes show a large positive drift and loss in selectivity in undiluted urine. The extraction of electrically neutral lipids from the urine into the sensing membrane was suggested as the main source of the drift, loss of selectivity and the consequent incorrect concentration readings.In this work, (i) solvent-solvent extraction, (ii) membrane-immobilized solvent extraction, and (iii) solid phase extraction were used to remove interfering compounds from urine samples. The "cleaned" urine samples were subsequently analyzed using a calixarene (sodium ionophore X)-based, solidcontact, sodium-selective electrode in a flow-through manifold. The solid-contact sodium sensors had excellent stability in cleaned urine and an acceptable bias compared to commercial clinical analyzers.

Characterization of optimized Na+ and Cl− liquid membranes for use with extracellular, self-referencing microelectrodes

“…Na + ionophore X has been used at less than 1% by weight in macroelectrode construction [8,9]. We found that 10% Na + ionophore X increased response time by more than an order of magnitude (Fig.…”

Mathematical Model of Current‐Polarized Ionophore‐Based Ion‐Selective Membranes: Large Current Chronopotentiometry

“…When these ion-selective membranes are brought in contact with a sample, such as whole blood, a two way equilibration process is initiated. In this process, the membrane components partition between the membrane (organic) and solution (aqueous) phases [3,4], and concurrently the solution components partition between the solution and the membrane [5,6]. In general, the highly hydrophobic nature of the membrane components minimize their partition into an aqueous electrolyte while the high concentration of anionic or cationic sites in the membrane prevent the partitioning of whole bathing salts, such as KCl, into the membrane [2].…”

Determination of urine ionic composition with potentiometric multisensor system

“…It is known [21] that organic components of urine can adsorb on a Table 1 The sum of standard deviations of sensor response in replicate measurements at different dilutions levels (mV).…”

“…An important issue is adsorption of organic urine components on a membrane surface, which leads to reduced reproducibility and lifetime of the sensors. The authors of [21] proposed to use solvent-solvent extraction, membraneimmobilized solvent extraction and solid phase extraction to remove lipophilic compounds from urine samples. However, such kind of sample preparation significantly reduces the benefits of sensors ensuring fast and simple analysis.…”