As can be seen, the concentration of Fe in the natural water samples ranged
from 0.32 mg 1–1 (drinking water of Vilnius city) to 2.2 mg 1–1 (rives Neris). Besides,
the comparison of the results obtained by both methods suggests that the
agreement between the two methods is satisfactory.
Preconcentration of iron from mineral water samples was necessary because
its concentration is usually too low to be determined directly by AAS. In order to
obtain accurate and precuse analytical results, an efficient preconcentration stepshould be performed before conducting the measurement. In the present study, an
extraction procedure for the concentration of the analyte has been suggested. To
demonstrate the suitability of the proposed method, the conditions for the extraction
of the Fe-8-oxyquinoline complex sith chloroform have been investigated.
Knowing that the extraction procedure involves the transfer of the complex
through the aqueous/organic phase interface and that the efficiency of this procedure
depends on the contact time, the effect of extraction time on the analytical signal
of the iron was estimated (Fig. 4).
As can be seen, the absorbance is stable already after 2 min. Consequently, this
time could be considered as the time necessary for complete extraction.
The effect of extractant volume on the analytical responses is shown in Fig. 5.
A variation of the analytical signal as a function of the extractant volume is evident.
From these results, 10 ml of chloroform was chosen as the otpimum volume.