Extraction—spectrophotometric determination of trace amounts of iron in waters with pyrogallol red and zephiramine

The simple removal of excess of co-extracted reagent in the solvent extraction of metal complex anions with a quaternary ammonium salt greatly improves the determination of iron(II) with pyrogallol red and zephiramine. The method with pyrogallol red is suitable for the determination of trace amounts of iron in natural waters. The apparent molar absorptivities of the iron(II) complex in chloroform are 7.5×10⁴ and 10.3×10⁴ 1 mol^-1 cm^-1 at 560 and 298 nm, respectively. A large excess of reagent can be added, and the ternary complex can be completely extracted over the pH range 8.5–10. Masking agents allow most interferences to be suppressed. The method is suitable for the analysis of potable, river and sea waters.