Determination of Iron in Environmental Water Samples by FIA-TLS

Dorota Korte,Arne Bratkič,Hana Budasheva,Gaja Tomsič,Mladen Franko

doi:10.17344/acsi.2018.4825

Dorota Korte, Arne Bratkič + Show 3 more

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https://doi.org/10.17344/acsi.2018.4825

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Abstract

The determination of low concentration of iron in natural waters can be difficult due to the complexity of natural water, but primarily because it requires preconcentration of the sample with solvent extraction. In this work we report on results of thermal lens spectrometry (TLS) coupled to flow injection analysis (FIA) as a highly sensitive FIA-TLS method of iron detection. The concentration of iron redox species was determined using 1,10-phenanthroline (PHN), that forms stable complexes with Fe(II) ions which are characterized by an absorption maximum at 508 nm. The TLS system using a 633 nm probe laser and 530 nm pump laser beam was exploited for on-line detection in flow injection analysis, where a PHN solution was used as the carrier solution for FIA. The concentration of the complexing agent affects the quality of the TLS signal, and the optimal concentration was found at 1 mM PHN. The achieved limits of detection (LODs) for Fe(II) and total iron were 33 nM for Fe(II) and 21 nM for total iron concentration. The method was further validated by determining the linear concentration range, specificity in terms of analytical yield and by determining concentration of iron in a water sample from a local water stream.

Highlights

As the fourth most frequent element in the earth’s crust, iron is a geologically important element
In this work we report on results of thermal lens spectrometry (TLS) coupled to flow injection analysis (FIA) as a highly sensitive FIA-TLS method of iron detection
The TLS system using a 633 nm probe laser and 530 nm pump laser beam was exploited for on-line detection in flow injection analysis, where a PHN solution was used as the carrier solution for FIA

Summary

Introduction

As the fourth most frequent element in the earth’s crust, iron is a geologically important element. Iron can be found in various forms in water: as dissolved, colloidal or particulate, either in the elemental form or in bivalent or trivalent ion forms, and in complexes.[1] The abundance of each species depends on the pH and Eh values of the aquatic environment. The oxidation state of iron affects the properties of the species, mobility and accessibility to organisms. The prevalent oxidation state is the divalent ion form Fe(II), which is soluble in water. It forms insoluble hydroxides, Fe(OH)[3]. Due to this phenomenon, the concentration of iron in natural water is very low

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