Determination of Cobalt in Natural Water as a 2-(5-Bromo-2-pyridylazo)-5-[N-propyl-N-(3-sulfopropyl)amino]phenol Chelate by On-Line Preconcentration HPLC with Column-Switching Technique

Abstract

Reversed-phase high performance liquid chromatography (RP-HPLC) with precolumn derivatization is a powerful method for the determination of trace amounts of metal ion because of its high sensitivity, simplicity, and low cost.1 However, some trace metal ions in natural water could not be determined by RP-HPLC directly. Combining with a suitable preconcentration technique is one of the effective ways to solve the problem.A solvent extraction 2-18 has been used commonly as the preconcentration technique for RP-HPLC. However, the off-line preconcentration methods like solvent extraction have some shortcomings, including low reproducibility, complicated procedure, and risk of contamination. To overcome these shortcomings, an on-line preconcentration technique with column switching has been proposed. [19][20][21][22][23] The flow system possesses high reproducibility, simplicity, and no contamination from atmosphere.In our previous paper 24 , cobalt(III)-2-(5-bromo-2-pyridylazo)-5-diethylamino]phenol (5-Br-PADAP) was preconcentrated by cation exchange resin for the determination of cobalt(II) by RP-HPLC. Although the preconcentration method enabled detection of 10 -10 mol dm -3 of cobalt(II), it could not avoid the shortcomings owing to the off-line methods. In this work, we investigate a valve-switching on-line preconcentration technique for HPLC determination to improve the previous work. The concentration of cobalt in natural water samples such as river water and seawater was determined with the on-line preconcentration HPLC. Experimental Reagents and apparatusAll reagents were of analytical reagent grade unless stated otherwise. A 5-Br-PAPS (Dojin Laboratories, Kumamoto, Japan) solution (5´10 -3 mol dm -3 ) was prepared by dissolving the reagent in water. A standard solution of Co(II) was prepared by dissolving cobalt nitrate in dilute nitric acid solution and standardized by ethylenediaminetetraacetic acid (EDTA) titration. Analytical-reagent grade methanol was purified by distillation. Water was purified with a Milli-Q system (Millipore) after distillation and deionization.The system used in this work comprised of a preconcentration part and an analytical part, which were combined with a six-port, two-way switching valve, as shown in Fig. 1. The preconcentration part consisted of a Nihon Seimitsu Kagaku (Tokyo, Japan) NP-DX8U pump, a Rheodine (Cotachi, USA) Model 7125 loop injector equipped with a sample loop of 1 cm 3 , and a concentration column (50 mm´4.6 mm i.d.) packed with Tosoh (Tokyo, Japan) TSKgel ODS 80 TM (C18 silica gel, particle size 5 mm). The analytical part consisted of a NP-DX 8U pump, a Hitachi (Tokyo, Japan) Model L-6000 spectrophotometric detector, a Hitachi -propyl-N-(3-sulfopropyl)amino]phenol (5-Br-PAPS) was used as a precolumn chelating agent for the determination of cobalt in natural water. Co(III)-5-Br-PAPS chelate was preconcentrated with the concentration column (50 mm´4.6 mm i.d.) packed with C18-silica gel sorbent by mean of a column-switching technique. The preconcentrated Co(III)...

Separation and Preconcentration of Cobalt after Sorption onto Amberlite XAD-2 Loaded with 2-(2-Thiazolylazo)-p-cresol

“…8,21 A complemental study revealed that cobalt(II) ions are not retained in a column loaded with TAC in the presence of reducing agents, such as ascorbic acid and hydroxylammonium chloride. In aqueous solution the cobalt(III) complex has green coloration and an absorption maximum at 576 nm.…”

Determination of Co(II) Ion as a 4-(2-Thiazolylazo)resorcinol or 5-Methyl-4-(2-thiazolylazo)resorcinol Chelate by Reversed-Phase Capillary High-Performance Liquid Chromatography

“…But, separation and simultaneous determination of mixtures of metal ions as their metal-chelates with an organic chelating reagent by reversed-phase high-performance liquid chromatography (RP-HPLC) had been accepted in inorganic analysis in recent years. [4][5][6][7][8] The organic chelating reagents, were 4-(2-pyridylazo)-resorcinol(PAR), 8,9 4-(2-thiazolylazo)-resorcinol (TAR), 4,7 2-(2-thiazolylazo)-p-cresol(TAC), 10 1-oxa-4,7,10,13-tetraazacyclopentadecane (OTAP), 11 and 2-(5-bromo-2-pyridylazo)-5-[N-propyl-N-(3-sulfopropyl)amino]phenol (5BrPSAA), 5 etc. TAR is the one of the popular chelating reagents.…”

Trace Determination of Metal Ions by On-Line Column Enrichment Followed by HPLC as Metal-2-(5-nitro-2-pyridylazo)-5-[N-propyl-N-(3-sulfopropyl)-amino]phenol Chelates

“…[5][6][7][8][9][10] Moreover, reversed-phase high-performance liquid chromatography (RP-HPLC) with precolumn derivatization is a powerful method for the determination of trace amounts of metal ions, because of its high sensitivity. [11][12][13][14][15][16][17] However, the concentration of some metal ions in water samples, such as rain, marine and tap water, are generally too low to be determined directly by RP-HPLC. [18][19][20] On the other hand, an ion-pair RP-HPLC using a counter cation has, also, usually been employed for the separation and determination of metal chelates.…”