Sol-Gel Functionalized Polyurethane Foam-Packed Mini-Column as an Efficient Solid Extractor for the Rapid and Ultra-Trace Detection of Textile Dyes in Water.

Textile dyes widely used in industrial products are known as a major threat to human health and water ecological security. On the other hand, sol gel represents a principal driver of the adoption of dispersive solid-phase microextractors (d-µ SPME) for pollutants residues in water. Thus, the current study reports a new and highly rapid and highly efficient hybrid sol-gel-based sponge polyurethane foam as a dispersive solid-phase microextractor (d-µ-SPME) platform packed mini-column for complete preconcentration and subsequent spectrophotometric detection of eosin Y textile dye in wastewater. The unique porous structure of the prepared sol-gel immobilized polyurethane foams (sol-gel/PUF) has suggested its use for the complete removal of eosin Y dye (EY) from water. In the mini-column, the number (N) of plates, the height equivalent to the theoretical plates (HETP), the critical capacity (CC), and the breakthrough capacities (BC) of the hybrid sol-gel-treated polyurethane foams towards EY dye were determined via the breakthrough capacity curve at various flow rates. Under the optimum condition using the matrix match strategy, the linear range of 0.01-5 µg L-1, LODs and LOQs in the range of 0.006 µg L-1, and 0.01 µg L-1 for wastewater were achieved. The intra-day and inter-day precisions were evaluated at two different concentration levels (0.05 and 5 µg L-1 of dye) on the same day and five distinct days, respectively. The analytical utility of the absorbents packed in pulses and mini-columns to extract and recover EY dye was attained by 98.94%. The column could efficiently remove different dyes from real industrial effluents, and hence the sol-gel/PUF is a good competitor for commercial applications. The findings of this research work have strong potential in the future to be used in selecting the most suitable lightweight growing medium for a green roof based on stakeholder requirements. Therefore, this study has provided a convenient pathway for the preparation of compressible and reusable sponge materials from renewable biomass for efficient removal of EY from the water environment.

Extractive Spectrophotometric Determination and Theoretical Investigations of Two New Vanadium(V) Complexes.

Two new vanadium (V) complexes involving 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR) and tetrazolium cation were studied. The following commercially available tetrazolium salts were used as the cation source: tetrazolium red (2,3,5-triphenyltetrazol-2-ium;chloride, TTC) and neotetrazolium chloride (2-[4-[4-(3,5-diphenyltetrazol-2-ium-2-yl)phenyl]phenyl]-3,5-diphenyltetrazol-2-ium;dichloride, NTC). The cations (abbreviated as TT+ and NTC+) impart high hydrophobicity to the ternary complexes, allowing vanadium to be easily extracted and preconcentrated in one step. The complexes have different stoichiometry. The V(V)-HTAR-TTC complex dimerizes in the organic phase (chloroform) and can be represented by the formula [(TT+)[VO2(HTAR)]]2. The other complex is monomeric (NTC+)[VO2(HTAR)]. The cation has a +1 charge because one of the two chloride ions remains undissociated: NTC+ = (NT2+Cl-)+. The ground-state equilibrium geometries of the constituent cations and final complexes were optimized at the B3LYP and HF levels of theory. The dimer [(TT+)[VO2(HTAR)]]2 is more suitable for practical applications due to its better extraction characteristics and wider pH interval of formation and extraction. It was used for cheap and reliable extraction-spectrophotometric determination of V(V) traces in real samples. The absorption maximum, molar absorptivity coefficient, limit of detection, and linear working range were 549 nm, 5.2 × 104 L mol-1 cm-1, 4.6 ng mL-1, and 0.015-2.0 µg mL-1, respectively.

Vanadium-Containing Anionic Chelate for Spectrophotometric Determination of Hydroxyzine Hydrochloride in Pharmaceuticals.

Four azo dyes known to form anionic complexes with V(V) were investigated as potential liquid-liquid extraction-spectrophotometric reagents for the antihistamine medication hydroxyzine hydrochloride (HZH). A stable ion-association complex suitable for analytical purposes was obtained with 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR). The molar absorption coefficient, limit of detection, linear working range, and relative standard deviation in the analysis of real pharmaceutical samples (tablets and syrup) were 3.50 × 104 L mol-1 cm-1, 0.13 µg mL-1, 0.43-12.2 µg mL-1, and ≤2.7%, respectively. After elucidating the molar ratio in the extracted ion-association complex (HZH:V = 1:1), the ground-state equilibrium geometries of the two constituent ions-HZH+ and [VO2(HTAR)]--were optimized at the B3LYP level of theory using 6-311++G** basis functions. The cation and anion were then paired in four different ways to find the most likely structure of the extracted species. In the lowest-energy structure, the VO2 group interacts predominantly with the heterochain of the cation. A hydrogen bond is present (V-O···H-O; 1.714 Å) involving the terminal oxygen of this chain.

Analytical optimization of liquid-liquid extractive spectrophotometric assessment protocol for tetravalent platinum: Analysis of environmental samples and cisplatin.

An easy and reliable method is optimized for extractive spectrophotometric assessment of platinum(IV) with 4-(4'-nitrobenzylideneimino)-3-methyl-5-mercapto-1,2,4-triazole as an extractant. The basis of this method is the formation of red platinum(IV) complex with the above reagent in acetate buffer medium (pH 5.0) and extraction in chloroform. Good linearity with regression equation as y = 1.011 × 104 ×  + 0.002 having correlation coefficient (R2) of 0.998 over concentration up to 17.5 µg mL-1 of platinum(IV) was achieved with apparent molar absorptivity of 1.011 × 104 L mol-1 cm-1. The limit of detection (0.22 µg mL-1), limit of quantification (0.73 µg mL-1) and Sandell's sensitivity (0.0193 µg cm-2) were also estimated. The interference of various cations was removed by using proper masking agents and consequently by using EDTA and citrate to mask certain transition metals, the method becomes highly specific for platinum(IV), including the effects of platinum group metals. The method is effectively used for determination of platinum(IV) from environmental and real samples such as alloys, catalysts, thermocouple wire and pharmaceutical sample.

Highly Efficient Spectrophotometric Determination of Cu2+ ion in Aqueous Medium Using a thiosemicarbazone-derivative Ligand.

A new simple spectrophotometric method for the determination of Cu2+ ion was developed using an thiosemicarbazone compound, 2-{4-[Bis(2-chloroethyl)amino]benzylidene}-N-[(4-methylthio)phenyl]hydrazinecarbothioamide (TSC). A simultaneous color change was observed (from colorless to bright yellow) by the addition of Cu2+ ion to the TSC ligand solution. The maximum absorbance of the TSC ligand measured at 366 nm was decreased by the presence of Cu2+ ion. The graphs of absorbance obtained by means of the Job's method and the molar-ratio method proposed a complex formation with a 1:2 Cu2+-TSC ligand stoichiometry. The molar-ratio method with emission measurements also confirmed the stoichiometry. The complex stability constant of TSC-Cu2+ complex (K) was evaluated to be 1.76 × 105. The proposed spectrophotometric method was associated with the change in absorbance at 366 nm owing to the interaction between the TSC ligand and Cu2+ ion. From the spectrophotometric titration data, it was pointed out that TSC ligand (1.5 × 10- 5 mol L-1) selectively reacted with Cu2+ ion in DMSO/water (1:1, v/v, citrate buffer at pH = 6.0). The calibration curve for Cu2+ ion was obtained with a good linearity in the range of 0.0191-0.3241 mg L-1. The detection limit for Cu2+ ion was 0.0063 mg L-1. The proposed method was achievemently implemented in real water samples (drink water, tap water and, distilled water). Satisfactory recoveries were confirmed at three different concentrations. The method presented a relative standard deviation (RSD%) of less than 3.08%.

A simple spectrophotometric determination of hydrogen peroxide solution via spectral delta from redox reaction with sodium hypochlorite.

Hydrogen peroxide (H2O2) is widely used in the synthesis of organic chemicals, bleaching of paper pulp, and the treatment of wastewater and as a food additive, important mediator of redox processes in natural water, and a disinfectant. However, H2O2 stock solution is unstable and slowly decomposes when exposed to, for example, light, elevated temperatures, or metal compounds. Therefore, the ability to measure the exact concentration of H2O2 stock solution is important for its proper use in diverse applications. This work proposes a simple method for the spectrophotometric determination of H2O2 solution via chemical reaction with sodium hypochlorite that is inexpensive and easy to acquire. The proposed method is based on the stoichiometric spectral change of hypochlorite ion at 292.5 nm following a redox reaction with a sample solution of H2O2. Due to high relationship between the spectral delta value and the applied H2O2 concentration (0.00188-0.03000%), H2O2 stock solution can be easily quantified.

Corrigendum: Radical scavenging capacity, antibacterial activity, and quantum chemical aspects of the spectrophotometrically investigated iridium (III) complex with benzopyran derivative.

[This corrects the article DOI: 10.3389/fphar.2022.945323.].

Radical scavenging capacity, antibacterial activity, and quantum chemical aspects of the spectrophotometrically investigated iridium (III) complex with benzopyran derivative.

A comprehensive aqueous phase spectrophotometric study concerning the trace level determination of iridium (III) by its reaction with benzopyran-derived chromogenic reagent, 6-chloro-3-hydroxy-7-methyl-2-(2'-thienyl)-4-oxo-4H-1-benzopyran (CHMTB), is performed. The complexing reagent instantly forms a yellow complex with Ir (III) at pH 4.63, where metal is bound to the ligand in a ratio of 1:2 as deduced by Job's continuous variations, mole ratio, and equilibrium shift methods. The complex absorbs maximally at 413-420 nm retaining its stability for up to 4 days. An optimum set of conditions have been set with respect to the parameters governing the formation of the complex. Under the set optimal conditions, the Ir (III)-CHMTB complex coheres to Beer's law between 0.0 and 1.5 µg Ir (III) mL-1. The attenuation coefficient and Sandell's sensitivity are, respectively, 1.18×105 L mol-1 cm-1 and 0.00162 µg cm-2 at 415 nm. The correlation coefficient (r) and standard deviation (SD) were 0.9999 and ± 0.001095, respectively, whereas the detection limit as analyzed was 0.007437 µg ml-1. The interference with respect to analytically important cations and complexing agents has been studied thoroughly. It is found that the majority of the ions/agents do not intervene with the formation of the complex, thus adding to the versatility of the method. The results obtained from the aforesaid studies indicate a simple, fast, convenient, sensitive, and versatile method for microgram analysis of iridium (III) using CHMTB as a binding ligand. Furthermore, the studied complex is subjected to the evaluation of antibacterial and antioxidant capacity by employing the Agar Diffusion assay and DPPH. radical scavenging method, respectively. The results obtained from the mentioned assays reveal that the investigated complex possesses significant potency as an antibacterial and antioxidant agent. Finally, the computational approach through DFT of the formed complex confirmed the associated electronic properties of the studied complex.

A simple and safe approach for simultaneous spectrophotometric determination of nitroglycerin and nitrocellulose in double base solid propellants.

An accurate, simple and safe method was developed for simultaneous determination of nitroglycerine (NG) and nitrocellulose (NC) in double base solid propellants (DB propellants). The proposed method is based on alkaline hydrolysis of NG and NC, and followed by colored reaction of released nitrite ion with p-nitroaniline in the presence of diphenylamine in acidic media and produce azo dye. The absorbance of the azo dye was measured at 534 nm. Two sets of reaction conditions were developed. In the first set, at room temperature, only NG was hydrolyzed and calibration curve obtained. In the second set, at 60 â„ƒ, NG and NC were hydrolyzed simultaneously. Based on obtained amount for the NG at room temperature, and total amount of NG and NC at 60 â„ƒ, the amount of NC was determined by using stoichiometric equations. The calibration curve was linear over the concentration ranges of 0.2-5.0, 0.5-10 µg mL-1 for NG and NC, respectively. The proposed method was successfully applied for the determination of NG and NC in DB propellants with good recoveries ranged from 99 to 101%, and RSD less than 2.0%. The method statistically compared based on t- and F-tests with those obtained in according to military standard method (MIL-STD-286). The results showed that the proposed method offers an accuracy and reliable approach for the determination of these compounds in DB propellants, and can be suggested as a routine method in military quality control laboratories.

Use of a Hydrophobic Azo Dye for the Centrifuge-Less Cloud Point Extraction-Spectrophotometric Determination of Cobalt.

The hydrophobic azo dye 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR, H2L) was studied as part of a system for the centrifuge-less cloud point extraction (CL-CPE) and spectrophotometric determination of traces of cobalt. The extracted 1:2 (Co:HTAR) complex, [CoIII(HL-)(L2-)]0, shows an absorption maximum at 553 nm and contains HTAR in two different acid-base forms. Optimum conditions for its formation and CL-CPE were found as follows: 1 × 10-5 mol L-1 of HTAR, 1.64% of Triton X-114, pH of 7.8, incubation time of 20 min at ca. 50 °C, and cooling time of 30 min at ca. -20 °C. The linear range, limit of detection, and apparent molar absorptivity coefficient were 5.4-189 ng mL-1, 1.64 ng mL-1, and 2.63 × 105 L mol-1 cm-1, respectively. The developed procedure does not use any organic solvents and can be described as simple, cheap, sensitive, convenient, and environmentally friendly. It was successfully applied to the analysis of artificial mixtures and real samples, such as steel, dental alloy, rainwater, ampoules of vitamin B12, and saline solution for intravenous infusion.

Supramolecular solvent-based liquid phase extraction of antimony prior to spectrophotometric quantification.

Antimony (Sb) is highly hazardous to human health even in minute concentration. Therefore, its accurate and precise determination in the real environmental samples is of immense importance. In this work for the first time, UV-Vis spectrophotometric method was developed for the quantification of Sb(III) from water samples using supramolecular solvent (undecanol-tetrahydrofuran)-based extraction. The maximum absorption wavelength for antomony-diathizone complex was found to be 590 nm having molar absorptivity of 3.1 × 104 L.mol.cm-1. Factors affecting extraction efficiency like solution sample volume, amount of chelating agent, pH, matrix effect, and type and volume of supramolecular solvent were determined and optimized. Analytical parameters like limit of detection (0.19 µg L-1), limit of quantification (0.62 µg L-1), pre-concentration factor (15), enhancement factor (15), and relative standard deviation for 8 successive analysis (0.8%) were calculated under optimized experimental conditions. The method was applied to real water samples like tap water of laboratory, waste water from Kohat hospitals, and dam water (Tanda dam Kohat) with quantitative addition recovery (94-100%).

Spectrophotometric Determination of Molybdenum(VI) as a Ternary Complex with 4-Nitrocatechol and Benzalkonium Chloride.

A new liquid-liquid extraction system for molybdenum(VI) was studied. It contains 4-nitrocatechol (4NC) as a complexing chromogenic reagent and benzalkonium chloride (BZC) as a source of heavy cations (BZ+), which are prone to form chloroform-extractable ion-association complexes. The optimum conditions for the determination of trace molybdenum(VI) were found: concentrations of 4NC and BZC (7.5 × 10-4 mol dm-3 and 1.9 × 10-4 mol dm-3, respectively), acidity (3.75 × 10-2 mol dm-3 H2SO4), extraction time (3 min), and wavelength (439 nm). The molar absorptivity, limit of detection, and linear working range were 5.5 × 104 dm3 mol-1 cm-1, 5.6 ng cm-3, and 18.6-3100 µg cm-3, respectively. The effect of foreign ions was examined, and the developed procedure was applied to the analysis of synthetic mixtures and real samples (potable waters and steels). The composition of the extracted complex was 1:1:2 (Mo:4NC:BZ). Three possible structures of its anionic part [MoVI(4NC)O2(OH)2]2- were discussed based on optimizations at the B3LYP/3-21G level of theory, and simulated UV/Vis absorption spectra were obtained with the TD Hamiltonian.

Zirconium (IV)-3-hydroxy-2-tolyl-4H-chromen-4-one complex-the analytical and DFT studies.

Trace determination of Zr(IV) was carried out by its complexation with a newly synthesized chromone derivative, 3-hydroxy-2-tolyl-4H-chromen-4-one (HToC) for the formation of a 1:4 (M:L) yellow-colored complex from the bicarbonate medium maintained at pH 7.90-8.13. The complex was extractable into the non-aqueous organic solvents showing maximum and stable color intensity in dichloromethane in the wavelength range 414-430 nm. The complex obeyed Beer's law showing linearity of calibration curve in the range 0.0-1.1 µg Zr(IV) ml-1 with an optimum range of determination as 0.44-1.0 ppm Zr(IV) detected from the Ringbom plot. Molar absorptivity, specific absorptivity, and Sandell's sensitivity of thus prepared complex were ascertained, respectively as 4.1971 × 104 l mol-1 cm-1, 0.4601 ml g-1 cm-1, and 0.0022 µg Zr(IV) cm-2 at 420 nm. The linear regression equation being [Formula: see text] (Y = absorbance, X = µg Zr(IV) ml-1) with the correlation coefficient of 0.9977 and detection limit of the procedure as 0.0729 µg ml-1. Theoretical calculations were used to determine and compare structural and bonding properties of the Zr(IV)-HToC complex along with justification of the donor sites provided by ligand for complexation with respect to the metal. The consequences obtained were highly cogent with standard deviation of ± 0.0021 absorbance unit. The procedure was applied to various synthetic (some analogous to cooperate and nickel zirconium) and technical (reverberatory flue dust and water) samples with satisfactory results.

Determination of N-Acetyl-l-cysteine Ethyl Ester (NACET) by Flow Injection Analysis and Spectrophotometric Detection Using Different Thiol-Sensitive Ligands.

A new flow injection spectrophotometric method for the determination of N-acetyl-l-cysteine ethyl ester (NACET) was developed and validated. The method is based on the reduction of Cu(II)-ligand complexes to chromophoric Cu(I)-ligand complexes with the analyte. The studied ligands were neocuproine (NCN), bicinchoninic acid (BCA) and bathocuproine disulfonic acid (BCS). The absorbance of the Cu(I)-ligand complex was measured at 458, 562 and 483 nm for the reactions of NACET with NCN, BCA and BCS, respectively. The method was validated in terms of linear dynamic range, limit of detection and quantitation, accuracy, selectivity, and precision. Experimental conditions were optimized by a univariate method, yielding linear calibration curves in a concentration range from 2.0 × 10-6 mol L-1 to 2.0 × 10-4 mol L-1 using NCN; 2.0 × 10-6 mol L-1 to 1.0 × 10-4 mol L-1 using BCA and 6.0 × 10-7 mol L-1 to 1.2 × 10-4 mol L-1 using BCS. The achieved analytical frequency was 90 h-1 for all three ligands. The method was successfully employed for NACET determination in pharmaceutical preparations, indicating that this FIA method fulfilled all the essential demands for the determination of NACET in quality control laboratories, as it combined low instrument and reagent costs with a high sampling rate.

A centrifuge-less cloud point extraction-spectrophotometric determination of copper(II) using 6-hexyl-4-(2-thiazolylazo)resorcinol.

A simple, cheap, and environmentally friendly centrifuge-less cloud point extraction procedure was developed for the preconcentration of traces of Cu(II) before its spectrophotometric determination. It is based on a complexation reaction with the hydrophobic azo reagent 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR), in which a complex with a stoichiometric ratio of 1:1 and an absorption maximum at 535 nm is formed. The experimental conditions for Cu(II) determination were found: HTAR concentration (8 × 10-6 mol mL-1), mass fraction of the surfactant Triton X-114 (2.2%), pH (5.9, ammonium acetate buffer), and incubation time (10 min at 60 °C). The linear range, limit of detection, molar absorption coefficient and preconcentration factor were calculated to be 4.5-254 ng mL-1, 1.34 ng mL-1, 2.54 × 105 L mol-1 cm-1, and 10, respectively. The effect of foreign ions was studied, and the proposed procedure was applied to the analysis of water samples and a saline solution for intravenous infusion.

Ethylenediamine-bound magnetite nanoparticles as dual function colorimetric sensor having charge transfer and nanozyme activity for TNT and tetryl detection.

A reusable, low-cost, and convenient ethylenediamine (EDA)-bound magnetite nanoparticles (MNPs)-based colorimetric sensor has been developed for dual function colorimetric determination of nitroaromatic explosives such as TNT and tetryl. Colorimetric detection of analytes may occur through two independent routes: (1) nano-Fe3O4- EDA- NH2 as σ-donor may interact with the σ- and π-acceptor aromatic-poly(NO2) groups to produce a colored charge-transfer (CT) complex; (2) nano-Fe3O4-EDA-NH2 as a Fenton-type nanozyme may generate reactive species that comprise hydroxyl radicals (•OH) with H2O2 to oxidize 3,3',5,5'-tetramethylbenzidine (TMB) to a blue-colored diimine (oxTMB-TMB) CT complex, where this color is bleached with TNT/tetryl because of donor-acceptor interactions between the explosive -NO2 groups and the -NH2 group of Fe3O4-EDA nanoparticles of restricted nanozyme activity. Both methods can quantify TNT well below the EPA recommended TNT residential screening level in soil, LOD being in the micromolar range. As EDA was covalently bound to MNPs, the same sensor can be separately reused six times for TNT and eight times for tetryl determination, using method (1). Common metal ions, anions, energetic materials, several camouflage materials, and soil components such as humates did not interfere with the nanosensor performance for TNT and tetryl. The combination of charge-transfer and nanozyme ability of Fe3O4- EDA-NH2 nanoparticles may bring a new approach to dual function colorimetric sensor design. To the best of our knowledge, this is the first dual function colorimetric sensor for TNT and tetryl using the same nanoparticles as sensing elements in two different detection systems involving either formation or bleaching of colored species. The proposed colorimetric sensor can determine nitroaromatic explosives in two different ways: method-1 for TNT and tetryl sensing with EDA-MNPs relies on the donor-acceptor interaction between the electron-deficient nitroaromatics and electron-rich amine groups covalently functionalized on MNPs to produce an absorbance at 512 nm. In method-2, EDA-MNPs having nanozyme activity react with H2O2 to form reactive species that can oxidize TMB to its blue-colored charge-transfer (CT) complex, where TNT and tetryl addition may partially inhibit the nanozyme activity of EDA-MNPs and cause color bleaching (decrement of 650 nm absorbance) by disrupting the CT complex formed from TMB. This is the first dual function colorimetric sensor for nitro explosives uniquely combining charge-transfer and nanozyme ability of EDA-Fe3O4 nanoparticles in the same nano-sensor.

Optimization of green and rapid analytical procedure for the extraction of patulin in fruit juice and dried fruit samples by air-assisted natural deep eutectic solvent-based solidified homogeneous liquid phase microextraction using experimental design and computational chemistry approach.

In this paper, a green and inexpensive air-assisted natural deep eutectic solvent-based solidified homogeneous liquid phase microextraction procedure was optimized for extraction of patulin in fruit juice and dried fruit samples using experimental design prior to its spectrophotometric determination. Four different natural deep eutectic solvent were prepared and applied to ensure efficient, and selective extraction of patulin. The significant variables including Zn(II) amount, cooling time, pH and amount of natural deep eutectic solvent were optimized by using central composite design. Under optimized conditions, working range was 10-750 µg L-1 with 0.9996 of correlation coefficient. Detection limit and preconcentration factor were 3.5 µg L-1 and 150, respectively. The repeatability and reproducibility precision were in the range of 3.2-4.6% and 4.3-5.6% respectively. Recoveries ranging from 94% to 104% proved the accuracy of the method. The optimized method was successfully applied to the extraction and identification of patulin in the selected samples.

A colorimetric probe based on 4-mercaptophenol and thioglycolic acid-functionalized gold nanoparticles for determination of phytic acid and Fe(III) ions.

As a first of its kind, we developed a highly sensitive colorimetric nanoprobe for phytic acid (PA) and Fe(III) ion detection based on 4-mercaptophenol (4MP) and thioglycolic acid (TGA)-functionalized gold nanoparticles {AuNPs@(4MP-TGA)}. AuNPs were easily derivatized by 4MP and TGA through -SH binding to gold. Fe(III) ions possibly are bound first to the phenolate groups of 4MP-AuNPs, and further coordinated several nanoparticles via the carboxylate groups of TGA-AuNPs to cause aggregation, resulting in a red-to-purple color change and a bathochromic shift in the SPR absorption band of the nanoprobe. With the addition of PA to the AuNPs@(4MP-TGA)-Fe(III) system, the aggregated particles were released due to strong complex formation between Fe(III) and PA, resulting in a restoration of the color (purple-to-red) and of the SPR band to the original 520 nm wavelength maximum. Thus, the 650-nm absorption is attenuated and the 520-nm band is enhanced upon PA-Fe(III) chelation. This means that the absorption ratio A650/A520 is an indication of Fe(III) whereas the reverse ratio A520/A650 of the PA content of complex samples. The limits of detection (LOD) of the AuNPs@(4MP-TGA) were 1.0 µM for Fe(III) ions and 0.15 µM for PA. Phytic acid extracted from bean grains was determined with the proposed probe, yielding good recoveries. In addition, common metal ions, anions, and several biomolecules did not show an adverse effect on the nanoprobe performance for ferric ions and phytate. The developed method was statistically validated against a LC-MS/MS literature method. Graphical abstract Mercaptophenolate (4MP)- and thioglycolic acid (TGA)-functionalized gold nanoparticles were prepared as nanoprobes to detect Fe(III) ions through nanoparticle aggregation accompanied by red-to-purple color shift. The same nanoprobe determined phytic acid in food through disaggregation of Fe(III)-aggregated nanoparticles by strong Fe(III)-phytate chelation and restoration of solution color from purple to red.

Determination of optimization parameters based on the Box-Behnken design for cloud point extraction of quinoline yellow using Brij 58 and application of this method to real samples.

Quinoline yellow (E104) dye is a food additive and generally used in cosmetics and drugs. In this work, polyethylene glycol hexa decyl ether (Brij 58) was used for the spectrophotometric determination of quinoline yellow (QY) in food and drug samples after cloud point extraction (CPE). Some parameters such as extraction temperature and time, pH, centrifuge speed, Brij 58 (surfactant) concentration, and Na2SO4 concentration were optimized using Box-Behnken design. The limit of detection (LOD) of this method was 0.0019 µg mL-1 for QY while the relative standard deviation (RSD) at low concentration levels (0.03 µg mL-1) was 1.32% (n = 5). Findings indicated that, this novel CPE method can be used quickly for the reproducible, selective and sensitive determination of QY dye in ordinary analysis.

Highly reproducible, simple and selective analytical method for extractive UV-visible spectrophotometric determination of ruthenium(III): Analysis of catalyst, fissium alloy and sequential separation.

An easy and selective method has been developed for the extractive spectrophotometric determination of ruthenium(III) with 4-(4'-flurobenzylideneimino)-3-methyl-5-mercapto-1,2,4-triazole (FBIMMT) as a chelating reagent. The basis of the method is the formation of stable complex of 'soft base' FBIMMT with 'soft acid' ruthenium(III). The reagent FBIMMT in n-butanol easily forms extractable yellow coloured complex with ruthenium(III) in acetate buffer of pH 4.8. The absorbance of [Ru(III)-FBIMMT] complex is measured at 394 nm against the reagent blank. Good linearity range of concentration up to 27.0 µg mL-1 of ruthenium(III) is attained with correlation coefficient R2 = 0.998. The optimum concentration range is 6 to 27.0 µg mL-1 which is deduced by Ringbom's plot. The apparent molar absorptivity found to be 2.75 × 103 L mol-1 cm-1. Some additional characteristics such as limit of detection (LOD = 0.48 µg mL-1), limit of quantification (LOQ = 1.19 µg mL-1), and Sandell's sensitivity (SS = of 0.0367 µg cm-2) are also estimated. The composition of [Ru(III)-FBIMMT] complex has been established from Job's continuous variation method, mole ratio method, and log-log plot method. The specificity towards ruthenium(III) is well studied and appropriate masking agents are applied wherever required to boost it. The intra-day and inter-day precision values are found to be brilliant with % relative standard deviation of 0.52 and 0.68 respectively with % accuracy within the range of 99.00-100. The method is effectively used for determination of ruthenium(III) from water samples, binary and ternary synthetic mixtures, fissium alloy samples and catalyst materials. A scheme for sequential group separation of ruthenium(III), palladium(II) and osmium(VIII) has also been developed. The reproducible results of the present method confirm that the method has a good potential for quantitative determination of ruthenium(III) from various matrices.