Extractive spectrophotometric determination of silver(I) at the 10−7M 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 × 106 l mol−1 cm−1 for a 200 ml volume of solution containing a silver(I), 3.65 × 106 for 400 ml of solution and 1.37 × 107 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 × 10−9 − 3 × 10−7 M silver(I) (0.16–12.9 μg of Ag+ in 400 ml); at the 2.25 × 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.