Table 15: Simultaneous second-order derivative spectrophotometric determination of Fe(II) and Co(II).

Amount taken (μg mL−1)Amount found* (μg mL−1)Relative error (%)
Fe(II)Co(II)Fe(II)Co(II)Fe(II)Co(II)

0.060.590.053 (96.3)0.572 (98.8)−3.6−2.8
0.120.590.120 (103.4)0.592 (100.5)3.440.5
0.230.590.230 (99.1)0.586 (99.4)−0.86−0.5
0.330.590.334 (101.2)0.572 (98.8)1.21−2.8
0.440.590.441 (100.2)0.590 (100.1)0.220.2
0.550.590.542 (98.5)0.586 (99.3)−1.45−0.5
0.330.590.328 (99.3)1.120 (94.9)−0.60−0.7
0.331.180.326 (89.6)2.280 (96.6)−1.21−5.0
0.332.360.324 (98.1)3.600 (101.7)−1.81−3.3
0.333.540.336 (101.8)4.670 (98.9)1.811.6
0.334.720.332 (100.6)4.670 (98.9)0.60−1.0

* Average of four determinations.