Simultaneous Analysis of Monovalent Anions and Cations with a Sub-Microliter Dead-Volume Flow-Through Potentiometric Detector for Ion Chromatography

Abstract

A microliter dead-volume flow-through cell as a potentiometric detector is described in this article for sensitive, selective and simultaneous detection of common monovalent anions and cations in single column ion chromatography for the first time. The detection cell consisted of less selective anion- and cation-selective composite membrane electrodes together with a solid-state composite matrix reference electrode. The simultaneous separation and sensitive detection of sodium (Na(+)), potassium (K(+)), ammonium (NH4 (+)), chloride (Cl(-)) and nitrate (NO3 (-)) in a single run was achieved by using 98% 1.5 mM MgSO4 and 2% acetonitrile eluent with a mixed-bed ion-exchange separation column without suppressor column system. The separation and simultaneous detection of the anions and cations were completed in 6 min at the eluent flow-rate of 0.8 mL/min. Detection limits, at S/N = 3, were ranged from 0.2 to 1.0 µM for the anions and 0.3 to 3.0 µM for the cations, respectively. The developed method was successfully applied to the simultaneous determination of monovalent anions and cations in several environmental and biological samples.

Using Potentiometric Electrodes Based on Nonselective Polymeric Membranes as Potential Universal Detectors for Ion Chromatography: Investigating an Original Research Problem from an Inquiry-Based-Learning Perspective

“…At this point, the students critically evaluated the features of the explored electrode as an IC detector and the future steps needed to accomplish the final implementation. For this purpose, a deeper study of relevant papers published in the literature that describe real uses of ion-selective electrodes as IC detectors was crucial. − …”

“…The main reason for searching for an IC detector different from the conductivity detector, which is the IC detector most widely used, is mainly related to the use of suppression columns, because the detector response strongly depends on the eluent’s background conductivity . Therefore, other approaches have been explored for this purpose, including potentiometry.…”

“…Isildak et al have been working for several years on this topic and have recently published a work based on the simultaneous analysis of monovalent anions (Cl − and NO 3 − ) and cations (Na + , K + , and NH 4 + ) with a potentiometric detector for IC. 33 The detector was composed of a microfluidic cell with a sample volume of 2 μL containing a reference electrode, one electrode based on an anion exchanger, and another electrode based on a cation exchanger. These electrodes were of the all-solid-state type and microsized.…”

“…+ . What is really remarkable is the potentiometric cell, 33 and an analogous design may be considered in future steps toward the real implementation of nonselective potentiometric electrodes as IC detectors. For this purpose, it is important to adapt the electrodes developed here to a solid-contact configuration.…”

“…33−39 The main reason for searching for an IC detector different from the conductivity detector, which is the IC detector most widely used, is mainly related to the use of suppression columns, because the detector response strongly depends on the eluent's background conductivity. 33 Therefore, other approaches have been explored for this purpose, including potentiometry. However, the majority of the examples found in the literature are based on the selective measurement of relevant targets rather than the simultaneous analysis of several ions, for which it is necessary to have nonselective detectors.…”