**2.1.2 Apparatus**

422 Macro to Nano Spectroscopy

determination of iron (II) and iron (III) were examined. The developed methods have been successfully applied to the determination of iron (II), iron (III) and total iron in water and ore samples. The methods were also verified by applying certified reference materials.

**2. A very sensitive flow-injection spectrophotometric determination method** 

Spectrophotometric detection based on the measurement of the absorbance at a characteristic wavelength of complex formed between a chelating agent and iron has been mainly applied (Kass M. and Ivaska A. 2002; Saitoh K., et al. 1998; Weeks D.A. and Bruland K.W. 2002; Giokas D.L., et al. 2002; Themelis D.G., et al. 2001; Bagheri H., et al. 2000; Molina-Diaz A., et al. 1998; Teshima N., et al. 1996; Tesfaldet Z.O., et al. 200); Udnan Y., et al. 2004; Morelli B., et al. 1983; Pojanagaroon T., et al. 2002; van Staden J.F. and Kluever L.G. 1998). A number of other chelating agents that have been reported for the spectrophotometric and/or flow-injection spectrophotometric determination of iron (III) and total iron include 2-thiobarbituric acid (Morelli B., et al. 1983), norfloxacin (Pojanagaroon T., et al. 2002), tiron (Mulaudzi L.V., et al. 2002; Van Staden J.F. and Kluever L.G. 1998), tetracycline (Ahmed M.J. and Roy U.K. 2009) and chlortetracycline (Sultan S.M. and Suliman F. 1992). Flow-injection spectrophotometric methods based on above chelating agents are not either selective, or a masking agent should be used (Wirat R., 2008). However, highly selective, simple and economical methods are still required for the routine determination of iron (II) in different sample matrices. An ultrasensitive and highly selective, rapid flow-injection spectrophotometric method for the determination of iron (II) and total iron has been proposed. The method was based on the reaction between iron (II) and 2', 3, 4', 5, 7-pentahydroxyflavone (Morin) in slightly acidic solution (pH:4.50) with a strong absorption at 415 nm. The chemical structure of Morin is shown Fig. 1. The reagent itself is sparingly soluble in water and does not absorb in the visible region of the spectrum, therefore, might be well suited for flow-injection analysis of iron (II) and total iron. The method has been successfully applied to the determination of iron (II) and

**for iron(II) and total iron using 2', 3, 4', 5, 7-pentahydroxyflavone** 

Fig. 1. The chemical structure of 2', 3', 4', 5', 7-pentahydroxyflavone (Morin)

All chemicals used were of analytical reagent grade or the highest purity available. Doubly distilled deionized water was used throughout the study. Glass vessels were cleaned by

total iron in water samples and ore samples.

**2.1 Experimental** 

**2.1.1 Reagent and standards** 

UV-Visible spectra of metal-AcSHA complexes were taken with a Unicam spectrophotometer (GBC Cintra 20, Australia). A Jenway 3040 Model digital pH-meter was used for the pH measurements.

In the FIA system, peristaltic pump (ISMATEC; IPC, Switzerland) 0.50 mm i.d. PFTE tubing was used to propel the samples and reagent solutions. Samples were injected into the carrier stream by a 7125 model stainless steel high pressure Rheodyne injection valve provided with a 20 L loop. The absorbance of the coloured complex formed (λmax 415 nm) was measured with a UV-Visible spectrophotometer equipped with a flow-through micro cell (Spectra SYSTEM UV 3000 HR, Thermo Separation Products, USA), and connected to a computer incorporated with a PC1000 software programme.

A UNICAM 929 model (Shimadzu AA-68006) flame atomic absorption spectrophotometer with deuterium-lamp background correction was used for the determination of iron in reference to the FIA method. The measuring conditions were as follows: UNICAM hollow cathode lamp, 10 cm 1-slot burner, air-acetylene flame (fuel gas flow-rate 1.50 L/min), 0.2 nm spectral bandwidth, and 7 mm burner height. The wavelength and the lamp current of Fe was respectively 248 nm and 5 mA.
