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Transient isotachophoresis of highly saline trace metals under strong electroosmotic flow conditions
Author(s) -
Riaz Asif,
Soo Chung Doo
Publication year - 2005
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.200406151
Subject(s) - isotachophoresis , electrolyte , chemistry , capillary action , detection limit , stacking , analyte , chromatography , capillary electrophoresis , analytical chemistry (journal) , resorcinol , reproducibility , hydroxymethyl , materials science , electrode , organic chemistry , stereochemistry , composite material
Transient isotachophoresis (TITP) is usually performed under low‐electroosmotic flow (EOF) conditions using a coated capillary or a low pH background electrolyte. We used a bare fused‐silica capillary for TITP stacking of anionic complexes of some heavy metals under high‐EOF conditions (pH 9.0). The sample component chloride as a leading electrolyte induced stacking by an isotachophoretic mechanism and the complexing agent 4‐(2‐pyridylazo) resorcinol (PAR) acted as a terminating electrolyte. The optimized background electrolyte was composed of 150 m M N ‐tris(hydroxymethyl)methyl‐3‐aminopropanesulfonic acid, 127 m M triethylamine, and 0.1 m M PAR at pH 9.0. The strong EOF at pH 9.0 pulled the analytes against their mobilities toward the outlet side, allowing a separation in the normal polarity mode. The stacking efficiency, reproducibility, analysis time, and sample loading capacity in coated and bare capillaries were compared. The stacking efficiency and reproducibility were higher and the analysis time was shorter in the coated capillary. However, a larger volume of a sample could be injected in the bare capillary to achieve detection limits comparable to those for the coated one without compromising the resolution between the analyte peaks. The limits of detection (S/N = 3) were in the sub‐ppb range for the selected metals (Fe 2+ , 0.3 ppb; Ni 2+ , 0.16 ppb; and Zn 2+ , 0.8 ppb) in a standard saline sample with 250 m M NaCl matrix. The proposed method was successfully applied to the analysis of reference urine samples and human urine samples.