Iron In Natural Waters Research Articles

Novel ionic reverse mixed micelle supramolecules in dispersive liquid-liquid microextraction for the successive/individual sensitive speciation analysis of iron in natural water by UV–Vis spectrophotometry

A sensitive UV–Vis spectrophotometry based procedure is delineated for ultra-trace speciation analysis of iron in natural waters. This study prepares and utilizes new ionic reverse mixed-micelles (i-RMMs) supramolecules for the coacervate microextraction of iron species successively or independently on field. The anionic dioctylsulfosuccinate-capric acid (DOSS-CA) and cationic Aliquat-336-capric acid (Aliquat-336-CA) RMMs are used as dispersing, ion-pairing and extractant, respectively for Fe(II) and Fe(III). In successive speciation, Fe(II) forms colourless Fe(II)-(phen)32+ at ng mL−1 level in weak acidic medium that reacts with anionic head groups of RMM and configurates as Fe(II)-(phen)32+-(DOSS-CA)2 ion-pair in inner hydrophilic core. This coloured ion-pair settles on the top as coacervate and leaves unreacted Fe(III) in bulk aqueous solution, which is extracted in the similar way as Fe(III)-(SCN)63−-(Aliquat-336-CA)3 ion-pair in strong acidic medium. The above strategy can be applied individually to Fe(III)/Fe(II). The iron species stabilized in coacervates are transported to laboratory for UV–Vis spectrophotometry detection. The pre-concentration and detection limits are 16 and 28; and 0.1 and 0.4 ng mL−1, respectively for Fe(II) and Fe(III). The recoveries are between 92 and 100% for both Fe(II) and Fe(III) at 100 ng mL−1. The accuracy is established by correlating the summation of discrete species concentration obtained with certified total iron of NIST CRMs 1643e and 1643f trace elements in water. This field oriented speciation is applied to real natural waters.

Nafion/platinum modified electrode-on-chip for the electrochemical detection of trace iron in natural water

Abstract A Nafion modified platinum electrode-on-chip for the electrochemical detection of iron in 0.1 M HCl has been demonstrated. The platinum electrode was patterned on a silicon substrate by a combination of microfabrication processes followed by spin coating deposition of a Nafion layer. The quality of the thin-film chip structure and the low surface roughness of the Nafion coated platinum nano-grains were observed by FE-SEM and AFM techniques. These features contributed to a significant improvement in the electrode performance in terms of sensitivity as it can offer: (i) a low and stable baseline current, (ii) a high faradic current with respect to the reduction of Fe3+. Under optimum conditions, the electrode operates in the range of 1 ppb to 250 ppb with a detection limit of 0.31 ppb. It also exhibits an excellent reproducibility with a relative standard deviation (RSD) of 6.11% for 20 repeated measurements. The electrode has been successfully applicable for detecting iron concentrations in natural water samples.

Determination of Iron in Environmental Water Samples by FIA-TLS

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.

Interferences by Natural Organic Matter in the determination of iron in natural waters by Flow Injection analysis with 1,10-phenanthroline

Interferences by Natural Organic Matter in the determination of iron in natural waters by Flow Injection analysis with 1,10-phenanthroline

Inactivation of E. coli and E. faecalis by solar photo-Fenton with EDDS complex at neutral pH in municipal wastewater effluents.

Photo-Fenton is a solar disinfection technology widely demonstrated to be effective to inactivate microorganisms in water by the combined effect of photoactivated iron species and the direct action of solar photons. Nevertheless, the precipitation of iron as ferric hydroxide at basic pH is the main disadvantage of this process. Thus, challenge in photo-Fenton is looking for alternatives to iron salts. Polycarboxylic acids, such as Ethylendiamine-N',N'-disuccinic acid (EDDS), can form strong complex with Fe3+ and enhance the dissolution of iron in natural water through photochemical process. The aim of this study was to evaluate the disinfection effectiveness of solar photo-Fenton with and without EDDS in water. Several reagent concentrations were assessed, best bacterial (Escherichia coli and Enterococcus faecalis) inactivation was obtained with 0.1:0.2:0.3 mM (Fe3+:EDDS:H2O2) in isotonic water. The benefit of using EDDS complexes to increase the efficiency of kept dissolved iron in water at basic pH was proven. Solar disinfection and H2O2/solar with and without EDDS, and Fe3+:EDDS complexes were also investigated. Bacterial inactivation results in municipal wastewater effluents (MWWE) demonstrated that the competitive role of organic matter and inorganic compounds strongly affect the efficacy of Fe3+:EDDS at all concentrations tested, obtaining the fastest inactivation kinetics with H2O2/solar (0.3 mM).

Adsorption-photometric determination of iron using silica with nitroso-R salt and nitroso-N salt functional groups

Adsorbents based on silica sequentially modified by polyhexamethylene guanidine and nitroso-R salt or nitroso-N salt are proposed for the preconcentration and adsorption-photometric determination of iron. It is shown that these adsorbents quantitatively recovered Fe(III) at pH 3.5–4.0 and Fe(II) at pH 4.5–7.0. In the adsorption of Fe(III) and Fe(II), intensely colored green complexes formed on the adsorbent surface. Based on the absence of signals in EPR spectra, it was concluded that iron in the oxidation state +2 was included into surface complexes with nitroso-R salt or nitroso-N salt. When Fe(III) interacted with nitroso-R salt or nitroso-N salt immobilized on the adsorbent surface, it was reduced to Fe(II). Diffuse reflection spectra of the surface complexes of iron(II) were broad bands with maxima at 720 and 710 nm. Procedures of the adsorption-photometric determination of iron in natural waters and snow samples were developed with the limit of detection of 0.05 μg of iron per 0.2 g of the adsorbent.

Enhancement of the Fenton and photo-Fenton processes by components found in wastewater from the industrial processing of natural products: The possibilities of cork boiling wastewater reuse

Some wastewaters from the industrial processing of natural products, such as cork boiling wastewater (CBW), have been known to contain high quantities of polyphenolic compounds that are capable of forming complexes with ferric and ferrous iron and even contributing to the reduction of ferric iron. The aim of this work is to evaluate how some of the major components found in CBW are able to influence the availability and regeneration of iron during the Fenton and photo-Fenton process, opening the way for its reuse. Presence of small quantities of CBW (1:50 related with wastewater to be treated) have been shown to increase availability of iron in natural water up to pH 5 and enhance the degradation of the insecticide Imidacloprid as well as a mixture of contaminants (phenol/methomyl/Imidacloprid) at near-neutral pH. Significant mineralization (>70%) of these compounds was also achieved at pH 5, with any added dissolved organic carbon (DOC) removed concurrently with the contaminants, with similar results to pH3 without CBW. The observed effects of the reused CBW are similar to the ones achieved by the addition of commercial iron-chelating agents such as Ethylenediamine-N,N′-disuccinic acid (EDDS) in photo-Fenton process.

Green Determination of Total Iron in Water by Digital Image Colorimetry

ABSTRACTA green iOS digital image colorimeter was fabricated for the determination of total iron in natural water. A mobile application operating on an iOS device was designed using Euclidean distance theory to perform iron determination. The application records the components of the color by storing red, green, and blue values as well as calculating the hue, saturation, brightness, and gray values using standard color theory. The component values obtained from the images of orange solutions of iron(II) complex with 1,10-phenanthroline were collected in a database and used for evaluation of the total iron concentration in water samples. Under the optimal conditions for solid-phase extraction used for sample preconcentration, the enrichment factor was 8.18. The iron concentration was determined by this device for concentrations from 0.01 to 1.0 ppm. The iOS digital image colorimeter achieved a limit of quantitation of 0.1 ppm. The accuracy and precision of the iOS digital image colorimeter were validated using a certified reference material, riverine water. The instrumentation was used for the analysis of natural water samples.

自然水中における鉄の化学種と生物利用性－鉄と有機物の動態からみる森・川・海のつながり－

食物連鎖の根底を担う藻類を含め生物にとって不可欠な微量元素である鉄は, 陸域から河川や地下水を経て下流に移行し, 沿岸域での基礎生産に貢献していると考えられている。本総説では, このような流域における鉄の生物地球化学動態について既往研究を整理した。鉄の化学的特性として, 中性pHでは無機第二鉄の溶解度はサブナノモーラーであること, 溶存有機物が鉄の溶解度を上昇させること, 種々の熱力学・光化学的反応が鉄の生物利用性と密接に関係することが明らかにされている。また, 微細藻類による鉄の生物利用性は鉄の化学種に強く依存するため, 陸域由来鉄が沿岸域の基礎生産に及ぼす影響を適切に評価するには, 鉄の化学種に着目して研究を進めていく必要がある。森・川・海のつながりにおける鉄と有機物の動態研究では, 陸での有機鉄の溶出から沿岸域生態系への移行までをカバーした総合的な研究が重要と考えられる。

Synthesis and characterization of a 3-hydroxy-4-pyridinone chelator functionalized with a polyethylene glycol (PEG) chain aimed at sequential injection determination of iron in natural waters

The synthesis of a highly water soluble 3-hydroxy-4-pyridinone ligand, functionalized with a hydrophilic ethylene glycol chain (PEG-HPO), was successfully achieved and is reported together with that of its iron(III) complex. The improved hydrophilicity of both the PEGylated 3,4-HPO ligand and its iron(III) complex were fully investigated in an analytical application and, the new chelator is proposed for the spectrophotometric sequential injection determination of iron in waters. The new ligand provided better sensitivity and a lower LOD for iron determination than that obtained for N-alkyl-3-hydroxy-4-pyridinone ligands. The developed sequential injection method presents a dynamic working range of 0.10–1.00mgFe/L with a LOD of 48μg/L. Due to the use of a sequential injection system, the overall effluent production was <2mL corresponding to the consumption of 44μg of PEG-HPO, 0.71mg of NaHCO3, 0.92mg of HNO3 and 500μL of sample. Two reference samples were assessed for accuracy studies and a relative deviation <5% was obtained; eight waters samples were analyzed and the results compared with the reference procedure, and no statistical difference was observed for the two sets of results.

ω-Thio nitrilotriacetic chemically modified gold electrode for iron determination in natural waters with different salinity

The preparation, characterization and analytical application of a chemically modified gold electrode (CME), based on ω-thio nitrilotriacetic acid derivative (N-[5-[[[[20-(acetylthio)-3,6,9-trioxaeicos-1-yl]oxo]carbonyl]amino]-1carboxypentyl]iminodiacetic acid) self-assembled monolayer (SAM), have been described. The electrode has been characterized by electrochemical techniques and tested for its response towards metallic ions, demonstrating to be effective for the determination of ionized iron at sub—μgL−1 level by differential pulse cathodic stripping voltammetry (DPCSV). The analytical response towards iron in natural water (tap water, marine water) and the interference of ions usually present and chelating agents (humic acids and EDTA as model ligand of high complexing capacity) have been evaluated.

Сорбционно-фотометрическое и тест-определение общего содержания железа в природных водах с использованием сорбентов на основе оксида циркония, модифицированного полигексаметиленгуанидином, феррозином и ференом С

Сорбционно-фотометрическое и тест-определение общего содержания железа в природных водах с использованием сорбентов на основе оксида циркония, модифицированного полигексаметиленгуанидином, феррозином и ференом С

Exploiting the use of 3,4-HPO ligands as nontoxic reagents for the determination of iron in natural waters with a sequential injection approach

In this paper, the use of 3-hydroxy-4-pyridinone (3,4-HPO) chelators as nontoxic chromogenic reagents for iron determination is proposed. The potential application of these compounds was studied in a sequential injection system. The 3,4-HPO ligands used in this work were specially designed to complex iron(III) at physiologic pH for clinical applications. The developed sequential injection method enabled to study the reaction conditions, such as buffering and interferences. Then, to further improve the low consumption levels, a microsequential injection method was developed and effectively applied to iron determination in bathing waters using 3,4-HPO ligands. The formed iron complex has a maximum absorbance at 460nm. The advantage of using minimal consumption values associated with sequential injection, together with the lack of toxicity of 3,4-HPO ligands, enabled to present a greener chemistry approach for iron determination in environmental samples within the range 0.10–2.00mg Fe/L with a LOD of 7μg/L. The overall effluent production was 350μL corresponding to the consumption of 0.48mg of 3,4-HPO ligand, 0.11mg of NaHCO3, 0.16mg of HNO3 and 50μL of sample. Three reference samples were assessed for accuracy studies and a relative deviation <5% was obtained. The results obtained for the assessment of iron in inland bathing waters were statistically comparable to those obtained by the reference procedure.

自然水中において腐植物質の化学的性質が第一鉄の酸化速度に及ぼす影響

本研究では自然水中に広く存在する腐植物質が第一鉄(Fe(II))の酸化速度に及ぼす影響を解明することを目的として, pH 8における溶存酸素(02)および過酸化水素(H2O2)によるFe(II)の各酸化速度定数(kO2およびkH2O2)を測定した. 酸化実験より得られた速度定数はいずれも腐植物質の種類により異なったが, 02による酸化速度は腐植物質存在下で増大した. また, kH202と腐植物質中の芳香族炭素割合およびカルボキシル基量との間にそれぞれ有意な相関が認められた. 本研究の結果から, 腐植物質との錯形成はFe(II)の酸化速度に影響を及ぼし, その程度は腐植物質中の鉄結合部位の種類, 量, 荷電特性等に依存することが示唆された.

Flow-Injection Determination of Iron Based on Its Catalysis on the Oxidation Reaction of Xylenol Orange by Potassium Bromate

A flow injection system is proposed for catalytic kinetic spectrophotometric determination of trace iron(II + III). The involved reaction is based on the catalytic effect of iron(III) on oxidation reaction of xylenol orange by potassium bromate to form a blue-violet complex. Iron(II) is also determined, being oxidized to iron(III) by potassium bromate. The calibration graph is linear in the range of 0.02–10.0 µg l−1 and 10.0–1100 µg l−1. The relative standard deviation is 1.5% for 4.0 µg l−1 iron(III) and 2.3% for 60.0µg l−1 iron(III) (n = 11). The presented system was applied successfully to the determination of iron in natural waters.

Determination of copper, lead and iron in water and food samples after column solid phase extraction using 1-phenylthiosemicarbazide on Dowex Optipore L-493 resin

A novel solid phase extraction procedure for determination of copper, lead and iron in natural water and food samples has been established in the presented work. 1-Phenylthiosemicarbazide (1-PTSC) as ligand and Dowex Optipore L-493 resin as adsorbent were used in a mini chromatographic column. Various analytical conditions for the quantitative recoveries of analyte ions including pH, amounts of adsorbent, eluent, sample volume, etc. were investigated. The recovery values for analyte ions were higher than 95%. The determination of copper, lead and iron was performed by flame atomic absorption spectrometry. The influences of some alkali, alkali earth and transition metals on the recoveries of analyte ions were investigated. The preconcentration factor was 62.5. The limit of detections of the understudied analytes (k=3, N=21) were 0.64μgL−1 for copper, 0.55μgL−1 for lead and 0.82μgL−1 for iron. The relative standard deviation was found to be lower than 6%. The accuracy of the method was confirmed with certified reference material (GBW 07605 Tea). The method was successively applied for the determination of copper, lead and iron in water and some food samples including cheese, bread, baby food, pekmez, honey, milk and red wine after microwave digestion.

Sequential injection trace determination of iron in natural waters using a long‐pathlength liquid core waveguide and different spectrophotometric chemistries

We developed a sequential injection analysis (SIA) method for the determination of iron in coastal, ground, and surface fresh waters using two different reagents (ferrozine and 1,10‐phenathroline). The methodology uses a double‐line SIA system to improve mixing conditions between sample and reagent solutions. A liquid wave‐guide capillary cell (LWCC) with 1.0 m pathlength, 550 µm i.d., and 250 µL internal volume was used to enhance the sensitivity of the determination. The detection limits for the ferrozine and 1,10‐phenanthroline reagent were 0.15 and 0.35 µg L−1, respectively. The system provides a linear response up to 20 µg L−1 and has a high throughput rate (41 h−1), low reagent consumption, and also low effluent production for both reagents. The developed method was applied to natural waters (river, well, ground, potable, and sea waters) and one reference water sample.

Superoxide Mediated Reduction of Organically Complexed Iron(III): Comparison of Non-Dissociative and Dissociative Reduction Pathways

We have investigated the mechanism of reduction of organically complexed iron(III) in the presence of superoxide, the one-electron reduced form of dioxygen that is produced in natural waters by thermal, photochemical, and biological pathways. Experimental results show that reduction of organically complexed iron(III) by superoxide may occur by either (or, in some instances, both) reaction of superoxide with inorganic iron(III) after its dissociation from the complex (dissociative reduction) or by direct reaction of superoxide with the complex (non-dissociative reduction). In the presence of low concentrations of ligands such as citrate and sulfosalicylate that bind iron(III) relatively weakly and result in complexes with high dissociation rate constants (kd > 1 x 10(-4) s(-1)), a dissociative reduction pathway dominates. However, in the presence of strong ligands or high concentrations of weak ligands, only non-dissociative reduction of complexed iron(III) occurs. The relative contribution of each pathway has major implications for the lability and hence potential bioavailablity of iron in natural waters. The simple kinetic model developed here can be used to correctly predict the superoxide-mediated formation rates of iron(II) in natural systems.

Establishment of heterodinuclear replacement complexation and its application to direct determination of iron in natural water with dibromo-o-nitrophenylfluorone

The chromophore dibromo-o-nitrophenylfluorone (DBNPF) was used to complex Fe(III) and Cu(II) at pH 5.88. Fe(III) can competitively replace Cu(II) from its dinuclear complex Cu(DBNPF)Cu, and forms the Cu(DBNPF)Fe heterodinuclear complex. The Fe-DBNPF and Cu-DBNPF complexes were also characterized by the spectral correction technique. The heterodinuclear replacement complexation (HRC) is proposed and first used for the quantitative detection of iron in trace level with high sensitivity and good selectivity by the light-absorption ratio variation approach. The limit of detection of Fe is 1.0 µg L−1. The method has been successfully applied to the direct determination of Fe(II, III) dissolved and bound to suspended substances in natural water.

Determination of dissolved iron(III) in estuarine and coastal waters by adsorptive stripping chronopotentiometry (SCP)

An adsorptive stripping chronopotentiometric (SCP) method has been developed for quantification of dissolved iron in estuarine and coastal waters. After UV-digestion of filtered samples the Fe(III) ions in non-deoxygenated samples were complexed with solochrom violet RS (SVRS). The complexes were then accumulated by adsorption on the surface of a mercury-film electrode. The stripping step was performed by applying a constant current of -17 microA. Sensitivity and detection limit were 15 ms nmol(-1) L (270 ms microg(-1) L) and 1.5 nmol L(-1) (84 ng L(-1)), respectively, for 60-s electrolysis time. Compared with the only other chronopotentiometric method available for measurement of iron in natural waters, our procedure is fifty times more sensitive in a quarter of the electrolysis time. It therefore enables detection of the concentrations currently found in estuarine and coastal waters. The method was successfully used to study the behaviour and seasonal variations of dissolved iron in the Penzé estuary, NW France.