Spectrofluorimetric determination of aluminum in drinking waters by sequential injection analysis

A selective procedure for the determination of Al³⁺ in drinking and natural waters is proposed. The analytical procedure is based both on the complex formation between Al³⁺ and 8-hydroxyquinoline-5-sulfonic acid (HQS) and on a fluorimetric detection of the complex. The reaction was carried out in presence of thioglycolic acid as a masking agent. This procedure has been adapted to a sequential injection analysis (SIA) system. Operative conditions both for batch and SIA procedures were investigated including reagent concentration, volumes, pH and wavelengths used for the fluorimetric detection. Batch procedure allows determination of Al³⁺ at ppb level (LOQ: 2.8 μg l⁻¹) within a working range of 2.2-300 μg l⁻¹. The SIA procedure was successfully employed for the determination of Al³⁺ in several commercial drinking and tap waters.     

Silver nanoparticles capped with 8-hydroxyquinoline-5-sulfonate for the determination of trace aluminum in water samples and for intracellular fluorescence imaging

We report on a simple method for the determination of traces of aluminum(III) in water at pH 7.4 by using silver nanoparticles (Ag-NPs) functionalized with 8-hydroxyquinoline-5-sulfonate. The modified Ag-NPs undergo (a) a distinct color change from yellow to deep orange, and (b) a strong fluorescence enhancement upon addition of Al(III). Both the ratio of absorbances at 530 and 392 nm, and the intensity of fluorescence at 492 nm can serve as the analytical information. The absorption-based calibration plot increases linearly in the 0.1 to 4.0 μM Al(III) concentration range. The detection limit is 2.0 nM which is much lower than the permissible level (7.4 μM) for drinking water as defined by the World Health Organization. The method was successfully applied to the determination of Al(III) in samples of lake water, tap water and boiler water, and the recoveries were from 98 to 105 %. The assay also was applied to the determination of Al(III) in living mouse myeloma cells via fluorescence imaging. A linear relationship was obtained between relative fluorescence intensity (F/F₀) and the concentration of Al(III) in the 0.05 μM to 4 μM concentration range. The detection limit is 15 nM.

An AIE and ESIPT active Schiff base as colorimetric probe of Fe3+ and turn-on fluorescent probe of Al3+: Experimental and theoretical studies

In this present study, a simple cation chemoprobe 1 bearing naphthol OH and imine group was designed and synthesized, which was identified as an aggregation induced emission (AIE) active molecule with excited state intramolecular proton transfer (ESIPT) features. In addition, 1 showed both colorimetric detection for Fe³⁺ and turn-on fluorescence response for Al³⁺. The binding ratio of 1 to Fe³⁺ and Al³⁺ were determined both to be 1:1 via Job’s plot and ESI-mass spectrometry analysis. The limit of detection (LOD) of probe 1 to Fe³⁺ and Al³⁺ were 0.10 and 0.43 μM, respectively. Moreover, probe 1 could be used to quantify Fe³⁺ and Al³⁺ in environmental water samples.     

1-[(2-Hydroxy-phenylimino)-methyl]-naphthalen-2-ol: application in detection and adsorption of aluminum ions

A novel “on–off” Al³⁺ ions fluorescence-enhanced sensor (E)-1-(((2-hydroxyphenyl) imino)methyl)naphthalen-2-ol (AH-2) and its hydrogel hybrid (PAMN) were synthesized. AH-2 showed excellent selectivity and ultrasensitive to Al³⁺ ions; the detection limit was 2.36?×?10^–9 M. The most plausible complexation mechanism was studied by ¹H NMR, FT-IR, HR-MS, Job’s plot and theoretical calculation. And, it was interesting that PAMN could adsorb Al³⁺ ions with a removal rate of over 99%, which also could easily be distinguished by the naked eye in UV lamp (365 nm). Before and after adsorption of Al³⁺ ions, the microstructures of PAMN were analyzed by scanning electron microscope and X-ray energy spectrometer. The silica gel detect plates prepared in this work could rapidly and conveniently detect Al³⁺ ions with a concentration greater than 5?×?10^–6 M (0.13 mg/L) in aqueous solution, and the detection concentration (0.13 mg/L) was lower than the national standard concentration of Al³⁺ ions (0.2 mg/L) in city tap water of china.

     

A metal–organic gel‐based fluorescent chemosensor for selective Al3+ detection

As an important metal element, aluminium has a significant impact on the environment and human health, and thus the detection of Al³⁺ has become the subject of much research. We synthesized a Ni(II)‐based metal–organic gel (Ni‐MOG), which can serve as an Al³⁺ fluorescence sensor with high selectivity and sensitivity, the limit of detection being calculated to be 0.5 μM. In addition, a composite film was further fabricated by hybridization of this Ni‐MOG with poly(vinyl alcohol). The composite film produced a rapid fluorescence response to Al³⁺ solutions at concentrations above 5 × 10^?5 M in 5 min. The Ni‐MOG composite film can also be successfully applied for the sensitive detection of Al³⁺ in real samples of tap water and seawater. The effective detection of Al³⁺ described in this contribution provides a new insight into water quality monitoring and has promising application value.     

Solvent-dependent chromogenic sensing for Cu and fluorogenic sensing for Zn and Al: a multifunctional chemosensor with dual-mode

A new multifunctional chemosensor 1 was synthesized and characterized by spectroscopic tools along with a single crystal X-ray crystallography. It can exhibit selective recognition responses toward Cu²⁺, Zn²⁺ and Al³⁺ in different solvent systems with bimodal methods (colorimetric and fluorescence). This sensor 1 detected Cu²⁺ ions through a distinct color change from colorless to yellow in aqueous solution. Interestingly, the receptor 1 was found to be reversible by EDTA. The detection limit (11 μM) of 1 for Cu²⁺ is much lower than WHO guideline (30 μM) in drinking water. In addition, the sensor 1 showed significant fluorescence enhancements in the presence of Zn²⁺ ion and Al³⁺ ion in two different organic solvents (DMF and MeCN), respectively. The binding modes of the three complexes were determined to be a 1:1 complexation stoichiometry through Job plot, ESI-mass spectrometry analysis, and ¹H NMR titration.     

Preparation of Silver Nanoparticles Reduced by Formamidinesulfinic Acid and Its Application in Colorimetric Sensor

A rapid one-step preparation approach of silver nanoparticles (AgNPs) was reported by employing formamidinesulfinic acid as reducing agent and soluble starch as stabilizing agent. The formation of AgNPs was further confirmed by using UV–Vis absorption spectroscopy, X-ray diffraction spectroscopy and transmission electron microscopy techniques. The resultant AgNPs could be directly used for the colorimetric reaction with metal ions. The results showed that Al³⁺, Cr³⁺, Fe³⁺ and Hg²⁺ ions could induce the color change of AgNPs from yellow to pink (Al³⁺), orange (Cr³⁺) and colorless (Fe³⁺ and Hg²⁺), respectively, which can be observed by the naked eye. Based on these, a sensitive colorimetric sensor for Al³⁺, Fe³⁺, Cr³⁺ and Hg²⁺ ions detection was developed.     

Separation and preconcentration of trace amounts of aluminum ions in surface water samples using different analytical techniques

A separation/preconcentration of aluminum (III) (Al³⁺) has been developed to overcome the problem of high matrix species, which may interfere with the determination of trace quantity of Al³⁺ in natural water samples. The separation of Al³⁺ in water samples was carried out from interfering cations by complexing them with 2-methyle 8-hyroxyquinoline (quinaldine) on activated silica. Whereas the separated trace amounts of Al³⁺ was preconcentrated by cloud point extraction (CPE), as prior step to its determination by spectrofluorimetry (SPF) and flame atomic absorption spectrometry (FAAS). The Al³⁺ react with 8-hydroxyquinoline (oxine) and then entrapped in non-ionic surfactant Triton X-114. The main factors affecting CPE efficiency, such as pH of sample solution, concentration of oxine and Triton X-114, equilibration temperature and time period for shaking were investigated in detail. The validity of separation/preconcentration of Al³⁺ was checked by certified reference material of water (SRM-1643e). After optimization of the complexation and extraction conditions, a preconcentration factor of 20 was obtained for Al³⁺ in 10 mL of natural water samples. The relative standard deviation for 6 replicates containing 100 μg L⁻¹ of Al³⁺ was 5.41 and 4.53% for SPF and FAAS, respectively. The proposed method has been applied for determination of trace amount of Al³⁺ in natural water samples with satisfactory results.     

Linear Schiff-base fluorescence probe with aggregation-induced emission characteristics for Al detection and its application in live cell imaging

A simple Schiff-base derivative with salicylaldehyde moieties as fluorescent probe 1 was reported by aggregation-induced emission (AIE) characterization for the detection of metal ions. Spectral analysis revealed that probe 1 was highly selective and sensitive to Al³⁺. The probe 1 was also subject to minimal interference from other common competitive metal ions. The detection limit of Al³⁺ was 0.4 μM, which is considerably lower than the World Health Organization standard (7.41 μM), and the acceptable level of Al³⁺ (1.85 μM) in drinking water. The Job's plot and the results of ¹H-NMR and FT-IR analyses indicated that the binding stoichiometry ratio of probe 1 to Al³⁺ was 1:2. Probe 1 demonstrated a fluorescence-enhanced response upon binding with Al³⁺ based on AIE characterization. This response was due to the restricted molecular rotation and increased rigidity of the molecular assembly. Probe 1 exhibited good biocompatibility, and Al³⁺ was detected in live cells. Therefore, probe 1 is a promising fluorescence probe for Al³⁺ detection in the environment.     

Sensitive and selective colorimetric detection of cadmium(II) using gold nanoparticles modified with 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole

We have developed a simple, sensitive and selective colorimetric method for the detection of cadmium(II) (Cd²⁺) using gold nanoparticles modified with 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole. Organic solvents or additives are not required. It is found that Cd²⁺ induces the aggregation of the modified Au-NPs via chelation, leading to a color change from red to blue. This change can be seen with bare eyes, and monitored by UV–vis spectroscopy, transmission electron microscopy and dynamic light scattering. The detection limit is 30 nM (at a signal-to-noise ratio of 3). The new approach was successfully applied to the detection of Cd²⁺ in spiked samples of tap water and lake water, and the results agree well with those obtained by flame atomic absorption spectroscopy.

Colorimetric detection of Fe3+/2+ and fluorescent detection of Al3+ in aqueous media: applications and DFT calculations

Abstract

A new multifunctional colorimetric and fluorescent chemosensor 1 for Fe^3+/2+ and Al³⁺ has been synthesized in the one-step procedure. The sensor 1 detected both Fe²⁺ and Fe³⁺ through the color change from yellow to brown and Al³⁺ via turn-on fluorescence. The binding stoichiometries of sensor 1 with Fe^3+/2+ and Al³⁺ were proposed to be 1:1 with the analyses of ESI-mass and Job plot. Importantly, the detection limits of 1 for Fe^3+/2+ (2.11 and 2.70 μM) and Al³⁺ (3.44 μM) were lower than the EPA guideline (5.37 μM) for Fe^3+/2+ and WHO guideline (7.41 μM) for Al³⁺. Compound 1 was used to quantify ferric species (Fe³⁺) in real samples. Moreover, the sensing processes for Fe^3+/2+ and Al³⁺ were proposed with the spectroscopic studies and theoretical calculations.     

Thiophene and diethylaminophenol-based “turn-on” fluorescence chemosensor for detection of Al3+ and F− in a near-perfect aqueous solution

A new fluorescent sensor 1, based on thiophene and diethylaminophenol moieties, has been synthesized and its binding capabilities for metal-ion and anion recognition were investigated. The sensor 1 showed ‘turn-on’ fluorescence in the presence of Al³⁺ and F^?. The sensing behaviors of 1 with Al³⁺ and F^? were studied by using photophysical experiments, ¹H NMR titration, and ESI-mass spectrometry analysis. The detection limits for the analysis of Al³⁺ and F^? were found to be 0.41 μM and 14.36 μM, respectively, which are below the WHO guidelines for drinking water (7.41 μM for Al³⁺ and 79 μM for F^?). Moreover, turn-on fluorescence of 1 toward Al³⁺ and F^? caused by intramolecular charge transfer (ICT) was well explained by density functional theory (DFT) calculations. Importantly, 1 could be used to detect Al³⁺ in the living cells.     

An Extractive‐Spectrophotometric Method for Determination of Fluoride Ions in Natural Waters Based on its Bleaching Effect on the Iron (III)‐Thiocyanate Complex

An extractive‐spectrophotometric method based on the bleaching effect of F^? ions on the iron (III)‐thiocyanate complex extracted into methyl iso‐butyl keton (MIBK) is proposed for the determination of fluoride ions in natural waters. This method is a simple and rapid method and there is no need for special and expensive reagents. The experimental conditions such as SCN^? concentration, pH and kind of solvent were optimized, and we found that 0.15 M SCN^?, pH = 5 and MIBK are the best selections. Limit of detection is 0.1 mg F^?/L with a linear dynamic range 0.5–7 mg/L which covers optimum concentration of F^? ions in drinking water (0.7–1.2 mg/L). Interference of Fe³⁺ and Al³⁺ ions was easily eliminated by the extractive procedure using a solution of oxine in chloroform. Finally, the proposed method was used in determination of fluoride content of some real water samples and the obtained results compared with those obtained from the standard method. No significant differences were observed between them.     

A colorimetric and fluorescent chemosensor for detection of Hg2+ using counterion exchange of cationic polydiacetylene

In this study, a colorimetric and fluorescent chemosensor for mercury ions (Hg²⁺) was developed. Cationic polydiacetylene (PDA) vesicles with a quaternary ammonium cation and iodide as a counterion show a blue-to-red color transition; the color change is accompanied by a fluorescence enhancement in selective response to Hg²⁺ ions because of a perturbation of the ene–yne conjugated backbone induced by counterion exchange. It allows for selective detection of Hg²⁺ with the naked eye and the sensor is used to determine Hg²⁺ concentrations in tap water samples.     

A highly sensitive and selective fluorescent probe for trivalent aluminum ion based on rhodamine derivative in living cells

A rhodamine spirolactam derivative (1) is developed as a colormetric and fluorescent probe for trivalent aluminum ions (Al³⁺). It exhibits a highly sensitive “turn-on” fluorescent response toward Al³⁺ with a 70-fold fluorescence intensity enhancement under 2 equiv. of Al³⁺ added. The probe can be applied to the quantification of Al³⁺ with a linear range covering from 5.0 × 10⁻⁷ to 2.0 × 10⁻⁵ M and a detection limit of 4.0 × 10⁻⁸ M. Most importantly, the fluorescence changes of the probe are remarkably specific for Al³⁺ in the presence of other metal ions, which meet the selective requirements for practical application. Moreover, the experiment results show that the response behavior of 1 towards Al³⁺ is pH independent in neutral condition (pH 6.0–8.0) and the response of the probe is fast (response time less than 3 min). In addition, the proposed probe has been used to detect Al³⁺ in water samples and image Al³⁺ in living cells with satisfying results.     

A Novel Al(III)‐Selective Electrochemical Sensor Based on N,N′‐Bis(salicylidene)‐1,2‐phenylenediamine Complexes

A polyvinylchloride membrane sensor based on N,N′‐bis(salecylidene)‐1,2‐phenylenediamine (salophen) as membrane carrier was prepared and investigated as a Al³⁺‐selective electrode. The sensor exhibits a Nernstian response toward Al(III) over a wide concentration range (8.0×10^?7–3.0×10^?2 M), with a detection limit of 6.0×10^?7 M. The potentiometric response of the sensor is independent of the pH of the test solution in the pH range 3.2–4.5. The electrode possesses advantages of very fast response and high selectivity for Al³⁺ in comparison with alkali, alkaline earth and some heavy metal ions. The sensor was used as an indicator electrode, in the potentiometric titration of aluminum ion and in determination of Al³⁺ contents in drug, water and waste water samples.     

Modified carbon paste electrode for potentiometric determination of aluminium ion in spiked real water sample

The present paper describes the development of a new chemically modified carbon paste electrode based on azithromycin (AMC) that considered as a selective aluminium recognition agent in the carbon paste electrode (CPE). This electrode was fully characterized in terms of composition, response time, usable pH range and temperature. The electrode exhibited a Nernstian response for Al³⁺ ion over a concentration range from 7.0 × 10^–6 to 1.0 × 10^–2 mol L^–1 with a slope of 21.3 ± 0.18 mV decade^–1 and the limit of detection was 6.0 × 10^–6 mol L^?1. It had a response time of about 6 s. The proposed sensor possesses a very good selectivity with respect to a variety of other cations. Finally this modified electrode was applied for the determination of the concentration of Al³⁺ ion in different water samples and the obtained results were comparable with those obtained with atomic absorption spectrometer (AAS).     

A fluorescent and colorimetric chemosensor for selective detection of aluminum in aqueous solution

We have synthesized a new Schiff base 1, which detects Al³⁺ through fluorescence and naked eye in aqueous solution. The sensor 1 exhibited selective and sensitive recognition toward Al³⁺ via significant fluorescence enhancement (31-fold). Moreover, it showed a significant color change from colorless to yellow. The complex formation was proposed to be 1:1 ratio, based on the Job plot, ESI-mass spectrometry analysis, ¹H NMR titration, and IR analysis. The detection limit was 1.00 μM, which is below the WHO acceptable limit (1.85 μM) in drinking water. In addition, the sensor 1 could be recyclable simply through treatment with a proper reagent such as EDTA.     

SERS as an analytical tool in environmental science: The detection of sulfamethoxazole in the nanomolar range by applying a microfluidic cartridge setup

Sulfamethoxazole (SMX) is a commonly applied antibiotic for treating urinary tract infections; however, allergic reactions and skin eczema are known side effects that are observed for all sulfonamides. Today, this molecule is present in drinking and surface water sources. The allowed concentration in tap water is 2·10⁻⁷ mol L⁻¹. SMX could unintentionally be ingested by healthy people when drinking contaminated tap water, representing unnecessary drug intake. To assess the quality of tap water, fast, specific and sensitive detection methods are required, in which consequence measures for improving the purification of water might be initiated in the short term. Herein, the quantitative detection of SMX down to environmentally and physiologically relevant concentrations in the nanomolar range by employing surface-enhanced Raman spectroscopy (SERS) and a microfluidic cartridge system is presented. By applying surface-water samples as matrices, the detection of SMX down to 2.2·10⁻⁹ mol L⁻¹ is achieved, which illustrates the great potential of our proposed method in environmental science.     

Determination of Cu2+ in Drinking Water Based on Electrochemiluminescence of Ru(phen)32+ and Cyclam

A convenient and simple electrochemiluminescence (ECL) method was employed to detect trace amounts of Cu²⁺ in drinking water. This method is based on the inhibitory effect of Cu²⁺ on the ECL of Ru(phen)₃²⁺ and 1,4,8,11‐tetraazacyclotetradecane (cyclam) system. ECL intensity of Ru(phen)₃²⁺ was considerably enhanced by the addition of cyclam because of the ECL reaction between them. The ECL intensity of Ru(phen)₃²⁺/cyclam system rapidy decreased with the addition Cu²⁺ because of the formation of chelate complex [Cu(cyclam)]²⁺. Good linear response (R ²=0.9948) was obtained at Cu²⁺ concentration of 1.0×10⁻⁹−1.0×10⁻⁵ mol ⋅ L⁻¹ at glassy carbon electrode in 0.1 mol ⋅ L⁻¹ phosphate buffer (pH 9.0). Observed detection limit of 4.8×10⁻¹⁰ mol ⋅ L⁻¹ satisfied the maximum contaminant level goal (MCLG) for Cu²⁺ set by the US Environmental Protection Agency (US EPA). Applicability of the proposed method was verified by the good reproducibility and stability of the method when applied to determine Cu²⁺ in tap water and simulated wastewater. Thus, a novel ECL detection method was developed for Cu²⁺ detection.