On-line determination of the trace amount of cobalt(II) in real samples by flame atomic absorption spectrometry method after pre-concentration by modified polyvinyl chloride

This work reports a simple and sensitive on-line solid-phase extraction system for the pre-concentration and determination of a trace amount of Co(II (ions by flame atomic absorption spectrometry (FAAS). This method is based on the on-line retention of cobalt ions with polyvinyl chloride modified by 3-(2-thiazolylazo)-2,6-diaminopyridine in a mini-column system. The retained Co(II) ions were eluted with 1.0 mol L-1 HCl, and direct aspiration to flame atomic absorption spectrometry (FAAS) for an accurate determination of it. The important experimental parameters such as the solution pH, length of column (adsorbent mass), sample flow rate, solvent eluent, type and concentration of the eluent, and co-existing ion effects were investigated in detail and optimized. Under the optimum conditions, the calibration graph was linear over the concentration range of 2-150 mu g L-1 for pre-concentration of 10.0 mL of the sample solution. The interassay precession (n = 6) was in the range of 1.8-5.2% at the concentration levels of 10.0, 50.0, 100.0, and 140.0 mu g L-1. The limit of detection and enhancement factor were 1.3 mu g L-1 and 40, respectively. The method was applied for determination of trace levels of Co(II) ions in different real samples such as tap water, waste water, vegetable, fruit, and drug with satisfactory results.