Determination of ammonium in wastewaters by capillary electrophoresis on a column‐coupling chip with conductivity detection

Abstract

Analytical potentialities of a chip-based CE in determination of ammonium in wastewaters were investigated. CZE with the electric field and/or ITP sample stacking was performed on a column-coupling (CC) chip with integrated conductivity detectors. Acetate background electrolytes (pH ∼3) including 18-crown-6-ether (18-crown-6) and tartaric acid were developed to reach rapid (in 7-8 min) CZE and ITP-CZE resolutions of ammonium from other cations (sodium, potassium, calcium and magnesium) present in wastewater samples. Under preferred working conditions (suppressed hydrodynamic flow (HDF) and EOF on the column-coupling chip), both the employed methods did provide very good repeatabilities of the migration (RSD of 0.2-0.8% for the migration time) and quantitative (RSD of 0.3-4.9% for the peak area) parameters in the model and wastewater samples. Using a 900-nL sample injection volume, LOD for ammonium were obtained at 20 and 40 μg/L concentrations in CZE and ITP-CZE separations, respectively. Very good agreements of the CZE and ITP-CZE determinations of ammonium in six untreated wastewater samples (only filtration and dilution) with the results obtained by a reference spectrometric method indicate a very good accuracy of both the CE methods presented.

Determination of low-molecular-weight amines and ammonium in saline waters by ion chromatography after their extraction by steam distillation

“…Ion chromatography [1,10,[23][24][25][26][27][28][29][30][31][32] has been also used for the determination of NH 4 + in waters in addition to spectrophotometry [33], CE [34], fluorimetry [14,35] and potentiometry [36,37]. Nevertheless, problems in the resolution of low molecular mass amine [1] and NH 4 + peaks as well as permanent damage of the column with consequent shortening of its life time can occur when high salinity water samples are directly analyzed [31].…”

Recent progress in analytical capillary isotachophoresis

“…The enrichment factors were up to 780‐fold compared to a conventional CZE mode using UV detection and the LODs were in the 15–27 nM range. Luc et al described the determination of ammonium in wastewaters by CE on a column‐coupling chip with conductivity detection and with electric field and/or ITP sample stacking. Under preferred working conditions (suppressed hydrodynamic flow and EOF), the employed methods provided very good repeatabilities for both model and wastewater samples.…”

Determination of chloride, sulfate and nitrate in drinking water by microchip electrophoresis

“…For example, in the field of water analysis only a limited number of relevant papers can be found [7,16,[24][25][26][27]32]. Bodor et al [7] reported on isotachophoresis (ITP) determination of chloride, nitrate, sulfate, nitrite, fluoride and phosphate at pH 3.5 on a poly(methylmethacrylate) (PMMA) microchip using contact conductivity detection.…”

“…Although we can see significant efforts in developments of MCE [7,12,14,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35], applications of this technology in analytical practice are still rather scarce. For example, in the field of water analysis only a limited number of relevant papers can be found [7,16,[24][25][26][27]32].…”