The selectivity of the glass slide
was examined for 60 ng mL1 of iron in the presence of a different
amount of foreign ions using the recommended method. An error
of less than or equal to ±5% in the absorbance reading was considered
tolerable. The results of the interference study were listed in
Table 2. Result specified that most of the common cations and
anions have no obvious influence on the determination of iron
even at high concentrations.