Simultaneous Determination of Inorganic Anions and Cations in Water and Biological Samples by Capillary Electrophoresis with a Capacitive Coupled Contactless Conductivity Detector Using Capillary Filling Method

Abstract

An analytical method for concurrent analysis of inorganic anions and cations has been developed using a capillary electrophoresis (CE)-capacitively coupled contactless conductivity detector (C 4 D) system. Although hydrodynamic and electrokinetic injection techniques have been widely used in CE, we employed a capillary filling method (CFM) for the analysis of inorganic ions. The procedure is relatively simple and has the advantage that CMF does not require pressure control and vial exchange. Three anions (chloride, sulfate, nitrate) and five cations (ammonium, potassium, sodium, magnesium, calcium) were successfully separated and detected at ppm levels within 80 s using a 9 mM histidine/15 mM malic acid (pH 3.6) containing 50 mM N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate as background electrolyte. Applying this analytical condition, the electroosmotic flow is negligible and anions and cations were migrated concurrently to different polarities according to their electrophoretic mobility. Obtained raw data showed stepwise increases in detected conductivity due to the migration of sample components, which expresses as peak profiles by differentiation of electropherograms. The RSD values of the peak area and migration times for the anions and cations were satisfactory and were less than 5.15 and 2.04%, respectively. The developed method was applied for the analysis of inorganic anions and cations in commercial mineral waters, tap water, urine, and exhaled breath condensate. These results indicate that the CE-C 4 D system with CFM is suitable for the rapid analysis of inorganic anions and cations in various samples. Keywords Capillary electrophoresis (CE), capacitively coupled contactless conductivity detector (C 4 D), capillary filling method (CMF), water analysis

Application of Capillary Electrophoresis for Determination of Inorganic Analytes in Waters

“…In order to move the cations towards the detector and prevent them from exiting the capillary at the injection end, a hydrodynamic flow towards the detector end was superimposed. In the capillary filling method, the separation capillary is filled with a sample containing anions and cations dissolved in BGE, and after a high voltage application, the anions and cations move to the appropriate electrode, based on their mobilities under conditions with suppressed EOF [85]. The analytes form boundaries and migrate towards the C 4 D detector.…”

“…In another attempt, the separation of cations and anions was achieved by gradient elution moving boundary electrophoresis (GEMBE) [57]. GEMBE is a technique that involves electrophoretic separation in a short-length capillary using continuous injection against a variable In the capillary filling method, the separation capillary is filled with a sample containing anions and cations dissolved in BGE, and after a high voltage application, the anions and cations move to the appropriate electrode, based on their mobilities under conditions with suppressed EOF [85]. The analytes form boundaries and migrate towards the C 4 D detector.…”

“…Capacitively-coupled contactless conductivity detection (C 4 D) is the most widely used and commercially available method. Yamamoto, 2019 [85] * value in parentheses-the effective length of capillary; C 4 D-capacitively coupled contactless conductivity detection, CE-capillary electrophoresis, CFM-capillary filling method, CTABcetyltrimethylammonium bromide, DDAPS-dodecyl-N,N-dimethyl-3ammonio-1-propanesulfonate, DOI-dual opposite end injection, GEMBE-gradient elution moving boundary electrophoresis, L effeffective length, PVA-polyvinyl acetate, LPA-linear polyacrylamide, SIA-sequential injection analysis, MES-2-(N-morpholino) ethanesulfonic acid, TTAB-tetradecyltrimethylammonium bromide, PDCA-2,6-pyridinedicarboxylic acid.6. Application of Microfluidic CE Systems.…”

Capillary and Microchip Electrophoresis

“…9,10 They found that the number of shot signals was reduced and a broad peak of the dispersed graphene became narrower upon the addition of PEG and dodecylbenzenesulfonate in a separation buffer. Yamamoto et al reported on a concurrent analysis of inorganic anions and cations filled in a whole capillary in CE-C 4 D. 11 Under a suppressed EOF, the migrations of anions and cations to different polarities gave a stepwise electropherogram. Differentiation of the electropherogram resulted in a series of peaks of the ionic analytes.…”

Analytical Chemistry by Electrophoresis

“…15 Takayanagi et al reported on the electrophoretic behavior of graphene, demonstrating that the dispersion of graphene in an aqueous solution can be monitored and that surfactant on the graphene surface is replaced competitively by water-soluble nonionic polymers. 16 CE and MCE can be connected with various detection methods [17][18][19][20] and analysis methods, such as mass spectrometry. This merit affords fruitful information about molecular species in a sample.…”