Spectrophotometric Determination of Iron(II) and Cobalt(II) by Direct, Derivative, and Simultaneous Methods Using 2-Hydroxy-1-Naphthaldehyde-p-Hydroxybenzoichydrazone

Table 4

Tolerance limits of some cations in derivative methods.

Foreign ion	Tolerance limit (in folds)
	Direct method	First derivative	Second derivative	Third derivative
Ag(I)	14	18	35	22
Hg(II)	11	20	40	30
U(VI)	11	12	25	18
Mn(II)	7	20	16	20
Th(IV)	5	10	16	20
In(III)	7	28	48	34
Au(III)	4	35	55	28
Sn(II)	<1	8	15	22
Co(II)	<1	interfere	7	15
Ni(II)	<1	interfere	5	10
Cu(II)	<1	5	12	10