SIMULTANEOUS PRECONCENTRATION AND DETERMINATION OF TRACE-ELEMENTS IN WATER SAMPLES BY COPRECIPITATION-FLOTATION WITH LANTHANUM HYDROXIDE [LA(OH)(3)]

The preconcentration and determination of trace Cd(II), Cu(II), Pb(II), Mn(II) and Zn(II) in water samples were studied by the precipitate flotation using La(OH)(3) as a coprecipitant. The analytes were quantitatively coprecipitated by adding 3.0 mL of 0.1 M La(III) solution in a 1,000 mL water sample and adjusting the pH to 9.5 with NaOH solution. After the addition of the 1:8 mixed surfactant solution of each 0.1% sodium oleate and sodium lauryl sulfate, the solution was stirred with a magnetic stirrer for 10 minutes. The precipitates were floated to the surface by bubbling with nitrogen gas and collected in a small sampling bottle. The precipitates were:dissolved in nitric acid and then the solutions were diluted to 25.00 mL with a deionized water. The analytes were determined by flame atomic absorption spectrometry. This procedure was applied to the waste water analysis. This technique was simple, convenient and especially rapid for the analysis of a large volume of sample. And also, from the recoveries of better than 92% which were obtained from rear samples, this method could be judged to be applicable to the preconcentration and quantitative determination of trace elements in water samples.