Abstract
The square-wave polarographic determination of lead by means of coprecipitation with zirconium hydroxide was previously reported {This journal, 22, 1346 (1973)}. The author have investigated polarographic determination of trace amounts of copper by means of coprecipitation with zirconium hydroxide. Hydroxides of thorium and zirconium was examined, and the latter was found to be the better collector of copper.
A square-wave polarograph of Shimazu type PR-50 was used, and the mercury pool at the bottom of the electrolytic cell was used as anode. The mercury flow-rate and drop time of the capillary were 2.058 mg s-1 and 3.62 s, respectively. The span voltage was 2.0 V and the gate range was 57. The following procedure is recomended:
To a solution (20 ml1000 ml) containing 0.60 μg, 3.15 μg of copper is added 5 mg of zirconium and pH is adjusted to 9.0 with ammonia water. The precipitate is separated by filteration and dissolved in 25 ml of 2 M hydrochloric acid. The solution is diluted to 50 ml with distilled water. A portion of this solution is submitted to the polarographic determination. The polarogram is recorded over the range from -0.10 V to -0.45 V vs. Hg-pool. Copper is determined from the wave at -0.26 V. The results are as follows:
(1) As shown in Fig. 3, a linear relationship exists between the copper concentration and the wave height over the range of 0.60 μg to 3.15 μg of copper.
(2) Zirconium hydroxide exerted the best effect in collecting copper when pH was adjusted to 9.0 with ammonia water.
(3) Temperature coefficient of the peak height of copper was +0.94%.
(4) Effects of various kinds of foreign ions is given in Table IV.
Cadmium ion does not interfere with the determination of copper but iron(III) and bismuth(III) ions interfere remarkably.
(5) The analytical procedure took about 4 hours and 0.002 ppm of copper in sample solution could be determined.
(6) According to Table V the coefficient of variation of this method was 0.53%.
