**6. Conclusions**

442 Macro to Nano Spectroscopy

different lengths ranging between 10 cm and 150 cm. The peak height increased with the increasing mixing coil length from 10–50 cm, decreased at lower concentrations and broadened at higher concentrations and longer coil lengths. The mixing coil length of 50 cm

The flow-rate was varied from 0.2 mL min*−*1 to 2 mL min*−*1. The peak height decreased with the increasing flow-rate, probably due to the extent of the reaction decrease. The flow-rate of 0.8 mL min*−*1 was selected as a compromise between the sample throughput rate and sensitivity. A linear calibration graph for 4–150 μg L*−*1 iron(III), with the regression coefficient of 0.9914, was obtained under optimum conditions. The relative standard deviation for the determination of 5 μg L*−*1 iron(III) was 0.85 % (10 replicate injections), RSD of the data was below 3 %. The limit of detection (blank signal plus three times the standard deviation of the blank) was 0.5 μg L*−*1. The sample throughput of the proposed method was

Over 50000 Cr(III), Al(III), Cd(II), Mn(II), K(I), Na(I), Ag(I), Ca(II), Mg(II),

The interference effects of many cations and anions on the determination of 5 μg L*−*1 iron(III) were examined. The results summarised in Table 8 represent tolerable concentrations of each diverse ion taken as the highest concentration causing an error of 3 %. Most of the ions examined did not interfere with the determination of iron(III). The major interference was caused by iron(II) at the amount of 100 μg L*−*1. It is known that zinc and cobalt are the main interference metal ions in the determination of iron (Ensafi et al., 2004). In this study, the interference of these ions was completely eliminated by an addition of copper sulphate (1*×*10*−*4 mol L*−*1) to the reagent carrier solution. Background absorbance of copper(II) maintained in the reagent carrier solution eliminated possible interfering ions and improved the determination of iron(III). It is apparent from Table 1 that the proposed method tolerates all interfering species tested in satisfactory amounts, and it is therefore adequately selective

The FIA method was applied in the determination of iron(III) and total iron in water and ore samples. In order to evaluate the accuracy of the proposed method, the determination of total iron in a standard reference material (Zn/Al/Cu 43XZ3F) and in a metal alloy sample was carried out. The analytical results obtained by the proposed method are in good

For the application of the proposed FIA method to water samples; river and sea water samples collected from different sources were analysed using both the calibration curve and the standard addition methods. The values obtained from the calibration curve and the standard addition methods are in good agreement as shown in Table 10. Atomic absorption

Table 8. Effect of foreign ions on the determination of 5 μg L-1 of iron (III) in solution

Ba(II), Hg(II), CN-, NO3-, NO2-, SO42-, CO32-, Cl-

, Br-, PO43-,

was chosen since it resulted in the best peak height and good reproducibility.

almost 60 h*−*1.

Tolerance limit (μg L-1) Foreign ion

for the determination of iron(III) and total iron.

agreement with the certified values as shown in Table 9.

**5.2.3 Applications** 

Over 100 Fe (II)

NH4+

A number of highly sensitive, selective and rapid flow-injection spectrophotometric and spectrofluorimetric analysis methods for the determination of iron (II), iron (III) and total iron in a wide concentration range, without employing any further treatment, have been described. The methods were based on the reactions of iron (II) and iron (III) with different complexing agents in different carrier solutions in FIA. In addition to the simplicity and low reagent consumption of the methods, the complexing agents used are commercially available and may not have a risk of serious toxicity, thus enhancing the potential applicability of the methods for iron analysis in real samples. Several parameters affecting to the determination of iron (II) and iron (III) were examined. The methods developed have been successfully applied to the determination of iron (II), iron (III) and total iron different types of water samples including river, sea, industry and spring water samples. The methods were also verified by applying certified reference materials.
