The repeatability and reproducibility of the method were eval-
uated by making repeat measurements on a sample under speci-
fied conditions. A relative standard deviation percentage (RSD, %)
for the intra-day precision (repeatability) was determined by per-
forming five replicate extractions and analysis of two concentra-
tions iron (100 and 300 lg L1
2.67–4.25%. A relative standard deviation percentage (RSD, %) for
the inter-day precision defined as reproducibility was calculated
by extractions on five consecutive days for analyzing two concen-
trations iron (100 and 300 lg L1
Slight change of temperature (±2 C) of the solution did not
produce significant variations for the result. The preconcentration
factor was obtained as the ratio between the sample volume of
the aqueous phase and the final volume (0.5 mL) of the enriched
organic phase and was found to be 10. The data obtained demon-
strate the proposed method has a broad linear range, high sensitiv-
ity and good precision. These RSD values testify to the excellent
ruggedness of the method.