Cobalt, determination with column preconcentration

A much more efficient, but less sensitive method for the determination of cobalt in sea water, tap water and waste waters by flame AAS with on-line column preconcentration was proposed by Fang et al.[14]. The column was packed with quinolin-8-ol immobilized on controlled pore glass. With dual columns, 48-fold sensitivity enhancement was achieved at a sampling frequency of 60 h , achieving a detection limit of 0.2 //g 1 ... 

Cobalt is determined by Sperling et al.flO] in sea water with a detection limit as low as 0.004 //g 1 using Cig column preconcentration FI-ETAAS. A still lower detection limit of 0.001 //g 1 was achieved by Porta et al.[l 1] using a similar approach, making it possible to determine cobalt in Antarctic sea water. 

Sakamoto [243] determined picomolar levels of cobalt in seawater by flow injection analysis with chemiluminescence detection. In this method flow injection analysis was used to automate the determination of cobalt in seawater by the cobalt-enhanced chemiluminescence oxidation of gallic acid in alkaline hydrogen peroxide. A preconcentration/separation step in the flow injection analysis manifold with an in-line column of immobilised 8-hydroxyquinoline was included to separate the cobalt from alkaline-earth ions. One sample analysis takes 8 min, including the 4-min sample load period. The detection limit is approximately 8 pM. The average standard deviation of replicate analyses at sea of 80 samples was 5%. The method was tested and inter calibrated on samples collected off the California coast. 

Chang et al. [952] used a miniature column packed with a chelating resin and an automatic online preconcentration system for electrothermal atomic absorption spectrometry to determine cadmium, cobalt, and nickel in seawater. Detection limits of 0.12,7 and 35 ng/1 were achieved for cadmium, cobalt, and nickel, respectively, with very small sample volume required (400-1800 xl). 

Preconcentration of trace cobalt with the ion pair of 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol and tetraphenylborate onto microcrystalline naphthalene or column method and its determination by derivative spectrophotometry has been described [5]. The method was applied to the determination of trace Co in alloys and biological materials. 

The first report on the use of ion-exchange columns with chemiluminescence detection was that by Buiguera et aI.[Sl] on the determination of zinc and cadmium through inhibition of the cobalt catalyzed chemiluminescence generation from luminol. The chloro-complexes of zinc and cadmium were retained by an anion exchanger and eluted separately using sodium hydroxide and nitric acid. Apparently, preconcentration effects were not pursued. 

Yamane et al.[13] determined cobalt in sea water and river waters with a catalytic spectrophotomeiric method after on-line preconcentration using a column packed with quinolin-8-ol immobilized on silica gel. The tartrate eluate from the preconcentraiion had to pass through a second column packed with a strongly acidic cation exchanger to remove iron(III) and manganese(II) which interfere in the catalytic reaction of oxidation of protocatechuic acid by hydrogen peroxide. An extremely low detection limit of 0.005 /ig 1 was obtained. However, the sampling frequency was less than 2 h . ... 

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