Iron(III) oxidized nucleophilic coupling of catechol with o-tolidine/p-toluidine followed by 1,10-phenanthroline as new and sensitivity improved spectrophotometric methods for iron present in chemicals, pharmaceutical, edible green leaves, nuts and lake water samples.

A nucleophile formed from iron(III) oxidized catechol in 0.1M hydrochloric acid couple with o-tolidine, system 1/p-toluidine, system 2 to produce dye product, λ max 520 nm. The system 1/2 obeys Beer's law in the range 0.08-8.0 μg ml(-1) with molar absorptivity, Sandell sensitivity and regression coefficient values, 4.225 × 10(3)/3.140 × 10(3) l mol(-1) cm(-1), 0.0132/0.0178 μg cm(-2) and 0.9987/0.9981. Iron(II) formed from iron(III) in system 1/2 reacts with 1,10-phenanthroline, λ max 510 nm, will constitute sensitivity improved iron determinations with values 0.08-1.6 μg ml(-1), 2.4136 × 10(4)/2.2511 × 10(4) l mol(-1) cm(-1), 0.0023/0.0025 μg cm(-2) and 0.9980/0.9997 corresponding to range, molar absorptivity, Sandell sensitivity and regression coefficient. The results of the systems for iron present in chemicals, pharmaceutical, edible green leaves, nuts and lake water samples are satisfactory since they are comparable with the results of iron determined separately from 1,10-phenanthroline method.