Extractive spectrophotometric determination of silver(I) at the 10(-7) M level using 1,10-phenanthroline and tetrabromophenolphthalein ethyl ester

The determination of silver(I) is based on the formation of a chelate of silver(I) with 1,10-phenanthroline and its extraction into 1,2-dichloroethane as an ion par with tetrabromophenolphthalein ethyl ester. Quantitative extraction of the ion pair was achieved when the volume of a solution containing silver(I) was varied over 10-1500 ml. The apparent molar absorptivities for silver(I) at 610 nm are 1.82 x 10(6) l mol(-1) cm(-1) for a 200 ml volume of solution containing a silver(I), 3.65 x 10(6) for 400 ml of solution and 1.37 x 10(7) for 1500 ml of solution, respectively. The absorbance of the extract is stable for at least one day in a glass-stoppered tube. A linear calibration graph was obtained over the range 3.6 x 10(-9)-3 x 10(-7) M silver(I) (0.16-12.9 mu g of Ag+ in 400 ml); at the 2.25 x 10(-7) M silver(I) level, the relative standard deviation (n=11) is 0.52%. The method was successfully applied to assays of silver in silver solder and silver protein samples: the results obtained were in good agreement with the stated values.