Development of a dispersive liquid-liquid microextraction method for iron speciation and determination in different water samples

Facile liquid colorimetric sensor using high-density deep eutectic solvent for trace detection and speciation of iron in milk

An efficient colorimetric sensor was developed using a high-density deep eutectic solvent (HD-DES) for the trace detection and speciation of iron in various milk samples. A liquid colorimetric probe was fabricated by dissolving ferrozine (FZ) in HD-DES prepared from TBABr and PBA. The prederivatization of Fe²⁺ via complexation with FZ on the HD-DES/FZ probe provided the [Fe(FZ)₃]^4- complex, which led to a color change from pale yellow to purple before it was simultaneously extracted by HD-DES. The Fe³⁺ content was calculated by subtracting the amount of Fe²⁺ from the total Fe content following the reduction of Fe³⁺ to Fe²⁺ by L-ascorbic acid in an acid buffer. Under the optimized conditions, the proposed colorimetric sensor exhibited appreciable linearity in the concentration range of 0.003-0.04 mg L^-1, a low limit of detection (0.95 µg L^-1), high enrichment factor (50), and outstanding repeatability. The liquid colorimetric probe was successfully applied for the determination and speciation of iron in milk samples, and the results were compared with those obtained using the standard atomic absorption spectrometry method. Moreover, quantitative analysis was performed on a smartphone using the Image J application to estimate the color intensity change, which eliminated the requirement of sophisticated scientific instruments.

Mutual Separation of Fe(II) and Fe(III) Using Cyclohexane/Water/Ionic-liquid Triphasic Extraction System with 2,2'-Bipyridine and Tri-n-octylphosphine Oxide

The triphasic extraction system with two extract phases can be used to separate two materials simultaneously into each phase. In this article, a possible mutual separation of Fe(II) and Fe(III) was studied using the cyclohexane/water/ionic liquid (IL) triphasic extraction system for Fe speciation. For Fe(II) and Fe(III) extraction, 2,2'-bipyridine (bpy) and tri-n-octylphosphine oxide (TOPO) were selected as extractants, respectively. It was suggested that [FeII(bpy)3]2+ and FeIII(TOPO)43+·3Tf2N- were extracted into the IL (1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, C4mimTf2N) phase and the cyclohexane phase, respectively, and both of the extractants also acted as masking agents. On simultaneous separation using the triphasic system, Fe(II) and Fe(III) were quantitatively extracted into the IL phase and the cyclohexane phase, respectively, and their mutual separation was achieved.

Detection of ferrous ion by etching-based multi-colorimetric sensing of gold nanobipyramids

Colorimetric sensing methods based on non-spherically symmetric gold (Au) nanoparticles have become a powerful tool in the field of biomedical detection due to their intriguing plasmonic properties. In this study, Au nanobipyramids (Au NBPs) were used as colorimetric sensing probes to detect ferrous ions (Fe²⁺) through tip etching. The quick etching of Au NBPs along the longitudinal direction by superoxide radicals generated by the reaction of Fe²⁺ and H₂O₂ led local surface plasmon resonance (LSPR) to blue shift and produced vivid color change that could be used for visual inspection. Under the optimal reaction conditions, the peak shift of the Au NBPs and the logarithm of the concentrations of Fe²⁺ had a linear relationship in the range of 10 nM to 10 μM, with a very low detection limit of 1.29 nM. During the etching process, a different end shape of the Au nanoparticles results in a different process for the morphology transition, which makes the degree of spectral change and detection sensitivity significantly different. In the presence of trace amounts of Fe²⁺ (<1000 nM), the detection sensitivity of Au NBPs with sharp ends which rely on aspect ratio and truncation is nine times higher than that of gold nanorods with round ends which only rely on aspect ratio. Although the color change of larger-sized Au NBPs was not clear during detection, the LSPR peak shift was more severe. Therefore, the system provides different modes for detecting Fe²⁺ according to Au NBPs with different sizes and characteristics.

Optimization of a methodology for determination of iron concentration in aqueous samples using a newly synthesized chelating agent in dispersive liquid-liquid microextraction

The aim of this study was to establish a new dispersive liquid-liquid microextraction (DLLME) technique for the determination of iron concentration in aqueous solutions and fruit juices based on the reaction between iron and 3-hydroxy-1-(3-hydroxyphenyl)-2-methylpyridin-4(1H)-one (3-OH-PMPO) as a chelating agent. A central composite design (CCD) was applied to optimize the effects of independent parameters (pH, volume of disperser solvent and extractant solvent and chelating agent concentration) on extraction efficiency. Under the optimized conditions, the analytical curve is linear in a concentration range of 10-750 μgL^-1 with a detection limit of 5 μgL^-1. The relative standard deviation (RSD) for ten repeated determinations of iron concentrations at 40 and 200 μgL^-1 was calculated to be 4.2% and 1.2%, respectively. Relative recovery of iron in several water samples was investigated and the average was obtained in the range of 91-108%.

A colorimetric-dispersive solid-phase extraction method for the sensitive and selective determination of iron using dissolvable bathocuproinedisulfonic acid-intercalated layered double hydroxide nanosheets

In this research, a novel, simple, sensitive and selective method has been presented for the determination of iron using dissolvable bathocuproine disulfonic acid (BCS)-layered double hydroxides (LDHs) for dispersive solid-phase extraction (DSPE).

Iron species determination by task-specific ionic liquid-based in situ solvent formation dispersive liquid-liquid microextraction combined with flame atomic absorption spectrometry

BACKGROUND

The task-specific ionic liquid (TSIL) of 1-ethyl-3-methylimidazolium bromide functionalized with 8-hydroxyquinoline was used as a chelating agent and extracting solvent for dispersive liquid-liquid microextraction and subsequent determination of Fe(III) by flame atomic absorption spectrometry. The in situ solvent formation of TSIL using KPF₆ provided the desired water-immiscible ionic liquid. The total Fe concentration could be determined after pre-oxidation of Fe(II) to Fe(III). Various factors affecting the proposed extraction procedure were optimized.

RESULTS

The proposed analytical conditions were: sample pH 5, TSIL amount 0.3% (w/v), KPF₆ amount 0.15% (w/v), anti-sticking 0.1% (w/v) and salt concentration 5% (w/v). Under optimal conditions, the linear dynamic ranges for Fe(III) and total Fe were 20-80 and 20-110 ng mL^-1 , respectively, with a detection limit of 6.9 ng mL^-1 for Fe(III) and relative standard deviation of 2.2%. The proposed method was successfully applied to the determination of trace Fe(III) in water (underground, tap, refined water and artificial sea water) and beverage (apple, tomato, and tea) samples.

CONCLUSION

The developed method offers advantages such as simplicity, ease of operation, and extraction of Fe(III) from aqueous solutions without the use of organic solvent. It was successfully applied for iron speciation in different real samples. © 2017 Society of Chemical Industry.

Fe3O4/hydroxyapatite/graphene quantum dots as a novel nano-sorbent for preconcentration of copper residue in Thai food ingredients: Optimization of ultrasound-assisted magnetic solid phase extraction

Fe₃O₄/hydroxyapatite/graphene quantum dots (Fe₃O₄/HAP/GQDs) nanocomposite was synthesized and used as a novel magnetic adsorbent. This nanocomposite was characterized using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and magnetization property. The Fe₃O₄/HAP/GQDs was applied to pre-concentrate copper residues in Thai food ingredients (so-called "Tom Yum Kung") prior to determination by inductively coupled plasma-atomic emission spectrometry. Based on ultrasound-assisted extraction optimization, various parameters affecting the magnetic solid-phase extraction, such as solution pH, amount of magnetic nanoparticles, adsorption and desorption time, and type of elution solvent and its concentration were evaluated. Under optimal conditions, the linear range was 0.05-1500ngmL^-1 (R²>0.999), limit of detection was 0.58ngmL^-1, and limit of quantification was 1.94ngmL^-1. The precision, expressed as the relative standard deviation of the calibration curve slope (n=5), for intra-day and inter-day analyses was 0.87% and 4.47%, respectively. The recovery study of Cu for real samples was ranged between 83.5% and 104.8%. This approach gave the enrichment factor of 39.2, which guarantees trace analysis of Cu residues. Therefore, Fe₃O₄/HAP/GQDs can be a potential and suitable candidate for the pre-concentration and separation of Cu from food samples. It can easily be reused after treatment with deionized water.

A Review on Recent Applications of High-Performance Liquid Chromatography in Metal Determination and Speciation Analysis

High-performance liquid chromatography (HPLC) has several advantages over the conventional methods due to their operational simplicity. It is a vital tool to determine metal ions having same mass but different electronic configuration, to separate complex mixtures and to resolve ions that may be indistinguishable by mass spectrometry alone. Metal ions play vital role in many biological processes and involved in setting up of many diseases. Therefore, the development of simple methods for the detection and quantification of metals in real samples might serve as diagnostic tools for various diseases. This review article focuses on the recent main feature of this technique, i.e. speciation of metal ions and their applications to series of problem of metal ion chemistry in different environmental matrixes. Speciation of metals is of increasing interest and has a great importance because of bioavailability, environmental mobility, toxicity and potential risk of metals. With the capability of partitioning the complex species of different metal ions, HPLC is an efficient technique for this task. This review summarizes recent advances in the development of HPLC to the fundamental understanding of metal ion chemistry in the environment and discusses all the issues that still need a lot of consideration. It has been classified into different sections depending on the role of HPLC in separation used and metal speciation; furthermore, the underlying sample preconcentration techniques and detection systems involved for the determination of metal ions and their applications were discussed.

Determination of iron (III) in food, biological and environmental samples

The nanodrop spectrophotometric (NDS) determination of iron (III) in water samples has been established. The proposed method is simple, selective and highly sensitive. The extraction of Fe (III)-thiocyanate complex was done by novel organic reagents such as N-phenylacetamide, N-alkylacetamide, (alkyl=butyl, hexyl and octyl group) in chloroform. The Fe (III) extract was examined in the strong acidic (HCl+H₂SO₄) solution. The maximum value of molar absorptivity was found to be 1.8×10⁵Lmol^-1cm^-1 at λ_max, 477nm (⩾9 fold enrichments) for N-octylacetamide (N-OAA). The method obeys the Beers Law within the range of 0.05μgmL^-1-6.0μgmL^-1. The detection limit and RSD value of the method were found to be 5ppb and 0.5906% respectively. The correlation coefficient, slope and intercept were calculated and found to be 0.9989, 0.1112, and 0.0048, respectively. The proposed method was successfully applied to the determination of trace amount of iron (III) in food, biological and environmental samples.

Ionic-liquid-based hollow-fiber liquid-phase microextraction method combined with hybrid artificial neural network-genetic algorithm for speciation and optimized determination of ferro and ferric in environmental water samples

A novel and environmentally friendly ionic-liquid-based hollow-fiber liquid-phase microextraction method combined with a hybrid artificial neural network (ANN)-genetic algorithm (GA) strategy was developed for ferro and ferric ions speciation as model analytes. Different parameters such as type and volume of extraction solvent, amounts of chelating agent, volume and pH of sample, ionic strength, stirring rate, and extraction time were investigated. Much more effective parameters were firstly examined based on one-variable-at-a-time design, and obtained results were used to construct an independent model for each parameter. The models were then applied to achieve the best and minimum numbers of candidate points as inputs for the ANN process. The maximum extraction efficiencies were achieved after 9 min using 22.0 μL of 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6MIM][PF6]) as the acceptor phase and 10 mL of sample at pH = 7.0 containing 64.0 μg L(-1) of benzohydroxamic acid (BHA) as the complexing agent, after the GA process. Once optimized, analytical performance of the method was studied in terms of linearity (1.3-316 μg L(-1), R (2) = 0.999), accuracy (recovery = 90.1-92.3%), and precision (relative standard deviation (RSD) <3.1). Finally, the method was successfully applied to speciate the iron species in the environmental and wastewater samples.

Simple and fast method for iron determination in white and red wines using dispersive liquid-liquid microextraction and ultraviolet-visible spectrophotometry

This work reports the development of a method for Fe extraction in white and red wines using dispersive liquid-liquid microextraction (DLLME) and determination by ultraviolet-visible spectrophotometry. For optimization of the DLLME method, the following parameters were evaluated: type and volume of dispersive (1300 μL of acetonitrile) and extraction (80 μL of C(2)Cl(4)) solvents, pH (3.0), concentration of ammonium pyrrolidinedithiocarbamate (APDC, 500 μL of 1% m/v APDC solution), NaCl concentration (not added), and extraction time. The calibration curve was performed using the analyte addition method, and the limit of detection and relative standard deviation were 0.2 mg L(-1) and below 7%, respectively. The accuracy was evaluated by comparison of results obtained after Fe determination by graphite furnace atomic absorption spectrometry, with agreement ranging from 94 to 105%. The proposed method was applied for Fe determination in white and red wines with concentrations ranging from 1.3 to 4.7 mg L(-1).

Dispersive liquid-liquid microextraction for the high performance liquid chromatographic determination of aldehydes in cigarette smoke and injectable formulations

A dispersive liquid-liquid microextraction method (DLLME) combined with high performance liquid chromatography (HPLC) was developed for the extraction and determination of some aldehydes, such as benzaldehyde (BzA), butyraldehyde (BuA) and furfural (Fur) in mainstream cigarette smoke as well as BzA in injectable formulations. After trapping of combustion smoke into sulfuric acid with a laboratory-made smoking machine, aldehydes were converted into their hydrazone derivatives by the reaction with 2,4-dinitrophenylhydrazine (DNPH), and then rapidly extracted by DLLME. The effects of various experimental parameters on the derivatization and extraction were studied and optimized. Under the optimum extraction conditions, linear calibration curves in the range 0.025 to 1.0 μg/mL with correlation coefficients of 0.9980-0.9996 were obtained for studied aldehydes. Limit of detections (LODs) for BzA, BuA and Fur were found to be 14.2, 21.3 and 7.92 μg/L, respectively. The relative standard deviations (RSDs) for inter-and intra-day assays were lower than 8.50%. Average recoveries for spiked samples were in the range 88.0-109%. The proposed method was successfully applied to the determination of aldehydes in different real samples.

Analysis of piroxicam in pharmaceutical formulation and human urine by dispersive liquid-liquid microextraction combined with spectrophotometry

PURPOSE

Piroxicam, is non-steroidal anti-inflammatory and analgesic agent, which is widely used in the treatment of patients with rheumatologic disorders. A new analytical approach based on the dispersive liquid-liquid microextraction (DLLME) has been developed for the extraction and determination of PX in pharmaceutical preparation and human urine.

METHODS

From the PX standard solution or solutions prepared from real samples, aliquot volumes were pipetted into centrifuge tubes and mixed with acetate buffer at pH 3.0 and NaCl solution. The contents were subjected to the DLLME, so 700 µL of methanol containing 70 µL of chloroform was injected rapidly into a sample solution. A cloudy solution was rapidly produced and the PX extracted into dispersed fine droplets. The mixture was centrifuged, thus these fine droplets of chloroform were settled. The supernatant aqueous phase was readily decanted, then the remained organic phase was diluted with ethanol and the absorbance measured at 355 ± 3 nm against a reagent blank.

RESULTS

The main factors affecting the extraction efficiency such as pH, extraction and disperser solvent types and etc. were studied and optimized systematically. Under optimized conditions, the calibration graphs were linear over the range of 0.2 to 4.8 µg/mL. The limit of detection and relative standard deviation were found to be 0.058 µg/mL and 2.83%, respectively. Relative recoveries in the spiked samples ranged from 97 to 110%.

CONCLUSION

Using the developed method PX can be analyzed in pharmaceutical formulation and human urine sample in a simpler, cheaper and more rapid manner.

An overview of liquid phase microextraction approaches combined with UV-Vis spectrophotometry

Ultraviolet and visible spectrophotometer has become a popular analytical instrument in the modern day laboratories. However, the low concentrations of many analytes in samples make it difficult to directly measure them by UV-Vis spectrophotometry. This overview focuses on the combinations of microvolume UV-Vis spectrophotometry with miniaturized approaches to sample preparation, namely, single drop microextraction (SDME), dispersive liquid-liquid microextraction (DLLME), cold induced aggregation microextraction (CIAME), in situ solvent formation microextraction (ISSFME), ultrasound assisted emulsification microextraction (USAEME), solidified floating organic drop microextraction (SFODME), and hollow fiber based liquid phase microextraction (HF-LPME) to improve both the selectivity and sensitivity. Integration of these techniques provides unique advantages which include availability, simplicity of operation, low cost, speed, precision and accuracy; hence making them a powerful tool in chemical analysis.

Spectrophotometric determination of iron species using a combination of artificial neural networks and dispersive liquid-liquid microextraction based on solidification of floating organic drop

A dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) and artificial neural networks method was developed for the simultaneous separation/preconcentration and speciation of iron in water samples. In this method, an appropriate mixture of ethanol (as the disperser solvent) and 1-undecanol (as the extracting solvent) containing appropriate amount of 2-thenoyltrifluoroacetone (TTA) (as the complexing agent) was injected rapidly into the water sample containing iron (II) and iron (III) species. At this step, the iron species interacted with the TTA and extracted into the 1-undecanol. After the phase separation, the absorbance of the extracted irons was measured in the wavelength region of 450-600 nm. The artificial neural networks were then applied for simultaneous determination of individual iron species. Under optimum conditions, the calibration graphs were linear in the range of 95-1070 μg L(-1) and 31-350 μg L(-1) with detection limits of 25 and 8 μg L(-1) for iron (II) and iron (III), respectively. The relative standard deviations (R.S.D., n=6) were lower than 4.2%. The enhancement factor of 162 and 125 were obtained for Fe(3+) and Fe(2+) ions, respectively. The procedure was applied to power plant drum water and several potable water samples; and accuracy was assessed through the recovery experiments and independent analysis by graphite furnace atomic absorption spectrometry.

Chelating agent free-solid phase extraction (CAF-SPE) of Co(II), Cu(II) and Cd(II) by new nano hybrid material (ZrO2/B2O3)

New nano hybrid material (ZrO(2)/B(2)O(3)) was synthesized and applied as a sorbent for the separation and/or preconcentration of Co(II), Cu(II) and Cd(II) in water and tea leaves prior to their determination by flame atomic absorption spectrometry. Synthesized nano material was characterized by scanning electron microscope, transmission electron microscope and X-ray diffraction. The optimum conditions for the quantitative recovery of the analytes, including pH, eluent type and volume, flow rate of sample solution were examined. The effect of interfering ions was also investigated. Under the optimum conditions, adsorption isotherms and adsorption capacities have been examined. The recoveries of Co(II), Cu(II) and Cd(II) were 96 ± 3%, 95 ± 3%, 98 ± 4% at 95% confidence level, respectively. The analytical detection limits for Co(II), Cu(II), and Cd(II) were 3.8, 3.3, and 3.1 μg L(-1), respectively. The reusability and adsorption capacities (32.2 mg g(-1) for Co, 46.5 mg g(-1) for Cu and 109.9 mg g(-1) for Cd) of the sorbent were found as satisfactory. The accuracy of the method was confirmed by analyzing certified reference material (GBW-07605 Tea leaves) and spiked real samples. The method was applied for the determination of analytes in tap water and tea leaves.