determination of iron with 1,10-phenanthroline?

Question

The standards prepared in lab contained only the iron phenanthroline complex. If the sample were more complexed, it could contain other compounds, some which might be colored, including some which might absorb light at the same wavelength as the iron phenanthroline complex. What problem would this cause?How could the procedure be modified to correct this problem?

Answer 1

A sample containing complexes of the chromogenic reagent (in this case phenanthroline) that absorb at the analytical wavelength will make the determined values of the analyte higher than they actually are ie the results will be biased upwards.

This problem can be corrected by :-

1. The use of a blank - a sample that contains all the interferences in the sample without the analyte of interest ie iron in this case.

2. The use of the method of standard addition. This is very useful for complex samples where it is difficult to replicate the sample matrix to make a blank.

Answer 2

That is a spectral interference. Spectrophotometer, due to its limitation, could not differentiate one compound from the other with the same wavelength. Also, the length of the slits are somewhat large, producing less effective in separating a specific wavelength.

Answer 3

The complex would not be properly identified. Also, in order to correct this, it must be stored in dark bottles or opaque containers.