1-hexylpyridinium Hexafluorophosphate Research Articles

Water molecular state in 1-hexylpyridinium hexafluorophosphate: Water mean cluster size as a function of water concentration

The water sorption behavior of representative pyridinium-based ionic liquid (IL), 1-hexylpyridinium hexafluorophosphate ([C6Py][PF6]), was studied over the whole range of the water activity a using a continuous gravimetric method. The analysis of the water sorption isotherm using the combination of a two-mode sorption (i.e. Henry-clustering) allowed to better understand [C6Py][PF6]-water interactions. At low and intermediate activity (a ≤ 0.8), the water molecules revealed a very low affinity to [C6Py][PF6] and, consequently, the water uptake was rather low. On the contrary, at high water activity (a > 0.8), the water uptake increased exponentially and the water clustering easily occurred. The constant of the Henry-clustering equation as well as the water clustering mechanism in [C6Py][PF6] were discussed and compared to those of imidazolium-based ILs: 1-hexyl-3-methylimidazolium hexafluorophosphate [C6C1im][PF6] (water-immiscible IL) and 1-butyl-3-methylimidazolium tetrafluoroborate [C4C1im][BF4] (water-miscible IL). It is shown that the sorption of water molecules by pyridinium-based ILs is controlled not only by the anion's nature, but also by the cation's nature. Moreover, the Zimm-Lundberg theory was used to determine the water mean cluster size (MCS) in [C6Py][PF6], [C6C1im][PF6] and [C4C1im][BF4]. The MCS results confirmed the strong capacity of water molecules to be aggregated in [C6Py][PF6]. In order to have a deeper insight into the water molecular state, infrared spectroscopy measurements were carried out as a function of the relative humidity value and the obtained results were correlated with the results of water sorption isotherms. It is found that at high water activity (a > 0.8), sorbed water molecules are strongly linked with ILs by hydrogen bonds and, therefore, are easily aggregated.

Highly sensitive determination of zileuton using TiO2 nanoparticles and the ionic liquid 1-hexylpyridinium hexafluorophosphate nanocomposite sensor

The highly sensitive electrochemical determination of zileuton on a nanocomposite sensor designed by incorporation of TiO2 nanoparticles and the ionic liquid 1-hexylpyridinium hexafluorophosphate (HPFP) has been reported. The capability of the modified electrode to quantify sub-micromolar concentrations of zileuton was investigated using adsorptive stripping differential pulse voltammetry (AdsDPV) as a sensitive electroanalytical method. Some kinetic parameters such as the electron transfer coefficient (α), the electron transfer number (n), and the standard electron transfer rate constant (ks) were also evaluated by cyclic voltammetry (CV) techniques. The influence of pH, sweep rate, accumulation time, and accumulation potential on the voltammetric response of zileuton was studied. Under the optimized conditions, the anodic peak current was linear for the concentration of zileuton in the broad range of 4.0 × 10−8 to 1.0 × 10−4 M with the detection limit of 8.3 × 10−9 M. In addition, using the amperometric technique the liner dynamic range of 1.0 × 10−5 to 1.4 × 10−4 M with detection limit of 1.8 × 10−6 M was obtained. This method was also successfully applied to detect the concentration of zileuton in human plasma and pharmaceutical dosage samples.

Gold Nanocage-Based Electrochemical Sensing Platform for Sensitive Detection of Luteolin.

A simple and sensitive electrochemical sensor was developed for the detection of tracelevels of luteolin. The sensoris based on a novel type of chemically modified electrode: gold nanocage (AuNCs)-modified carbon ionic liquid electrode (CILE). To construct this electrochemical sensing platform for luteolin, CILE is initially prepared by using 1-hexylpyridinium hexafluorophosphate as the binder and then AuNCs are coated on the surface of CILE to fabricate AuNCs-modified CILE (AuNCs/CILE). Electrochemical studies have shown that AuNCs/CILE can exhibit enhanced electrocatalytic activity toward the redox reaction of luteolin, therefore, the redox peak current of luteolin can be greatly improved, resulting in the high sensitivity of the developed sensor. Under the optimal conditions, the oxidation peak currents of the sensor increase linearly with an increase in the luteolin concentration in a range from 1 to 1000 nM with a detection limit of 0.4 nM, which is lower than those of most reported electrochemical luteolin sensors. Moreover, the reproducibility, precision, selectivity, and stability of this sensor are excellent. Finally, the sensing system was applied to the analysis of luteolin-spiked drug samples and the recovery in all cases was 95.0–96.7%, indicating the potential application of this simple, facile, and sensitive sensing system in pharmaceutical analysis.

Electrooxidation study and highly sensitive voltammetric determination of alfuzosin employing multi-walled carbon nanotubes and the ionic liquid 1-hexylpyridinium hexafluorophosphate nanocomposite sensor

By using several electrochemical techniques, the voltammetric behavior of alfuzosin (AFZ) based on the oxidation at the carbon nanocomposite electrode designed by incorporation of multi-walled carbon nanotubes (MWCNT) and the ionic liquid 1-hexylpyridinium hexafluorophosphate (HPFP) has been reported. Various characteristics of the electrode were studied by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Differential pulse voltammetry (DPV) was applied as a sensitive procedure for the quantitative determination of AFZ. Concerning optimized experimental conditions, the proposed electrode exhibited substantial sensitivity toward determination of AFZ. Good linearity in the wide range of 2.0×10−8 to 9.0×10−5M was obtained with the detection limit of 4.1×10−9M. Similarly for the amperometric procedure the liner range of 1.0×10−5 to 1.0×10−4M with detection limit of 2.1×10−6M was achieved. To acquire more information about the reaction mechanism and estimating some kinetic parameters, cyclic voltammetry (CV) studies was also performed. The oxidation was irreversible and showed adsorption controlled behavior. The method was successfully applied for the determination of AFZ content in plasma samples.

Ultrasonic assisted ionic liquid based microextraction for preconcentration and determination of aluminum in drinking water, blood and urine samples of kidney failure patients: Multivariate study

We have developed a simple ultrasonic-assisted ionic liquid-based microextraction (US-ILME) method for trace levels of aluminum (Al3+), in water, blood, and urine samples, followed by atomic absorption spectrometry with a nitrous oxide–acetylene flame. An ionic liquid, 1-hexylpyridinium hexafluorophosphate [Hpy][PF6], was used as the extraction solvent, and 8-hydroxyquinoline (oxine), was used as the Al3+ chelating agent. A multivariate strategy was employed to evaluate five factors/variables (concentration of the chelating agent, pH, amount of ionic liquid, sonication time and centrifugation time) at once, whereas a central composite design was used to find the optimum values of the significant variables. The multivariate strategy was used to estimate the optimum values of experimental factors that influence the efficiency of US-ILME. Under the optimum experimental conditions, the limit of detection (3 s) and enrichment factor were 0.66 μg L−1 and 113, respectively. The relative standard deviation (RSD) for six replicate determinations of 10 μg L−1 of Al3+ was 1.7%. The method was validated by the analysis of certified reference materials and applied successfully to the determination of Al3+ in different types of drinking water, and in blood and urine samples of kidney failure patients. The data indicated that the levels of Al3+ were significantly higher in kidney failure patients compared with healthy referents (p < 0.01).

Electrochemical behavior and voltammetric determination of p-methylaminophenol sulfate using LiCoO2 nanosphere modified electrode

In this study, LiCoO2 nanoparticles were synthesized by the hydrothermal method and characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction analyses, which exhibited flower-like nanospheres composed of uniform nanosheets. The synthesized LiCoO2 nanospheres were further used for the modification of 1-hexylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE). The electrochemical performance of the modified electrode, LiCoO2/CILE, was studied by cyclic voltammetry and electrochemical impedance spectroscopy. Electrooxidation of p-methylaminophenol sulfate (metol) on the modified electrode was further tested and electrochemical responses of metol were significantly enhanced owing to the presence of LiCoO2 nanospheres with large surface area and fast electron transfer rate. The electrochemical parameters such as the charge transfer coefficient, the number of electron transferred, the standard electrode reaction rate constant, and the apparent diffusion coefficient for metol electrooxidation were calculated as 0.51, 0.91, 0.92s−1 and 7.06×10−5cm2/s, respectively. Under the optimized conditions, metol can be linearly detected in the concentration range from 0.4 to 400.0μmol/L with a detection limit of 2.46×10−7mol/L (3σ). The optimized method was further applied to the detection of metol content in artificial wastewater samples with satisfactory results.

Electrodeposited nickel oxide and graphene modified carbon ionic liquid electrode for electrochemical myglobin biosensor

By using ionic liquid 1-hexylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE) as the substrate electrode, graphene (GR) and nickel oxide (NiO) were in situ electrodeposited step by step to get a NiO/GR nanocomposite modified CILE. Myoglobin (Mb) was further immobilized on the surface of NiO/GR/CILE with a Nafion film to get the electrochemical sensor denoted as Nafion/Mb/NiO/GR/CILE. Cyclic voltammetric experiments indicated that a pair of well-defined quasi-reversible redox peaks appeared in pH3.0 phosphate buffer solution with the formal peak potential (E0′) located at −0.188V (vs. SCE), which was the typical characteristics of Mb Fe(III)/Fe(II) redox couples. So the direct electron transfer of Mb was realized and promoted due to the presence of the NiO/GR nanocomposite on the electrode. Based on the cyclic voltammetric data, the electrochemical parameters of Mb on the modified electrode were calculated. The Mb modified electrode showed an excellent electrocatalytic activity towards the reduction of different substrates including trichloroacetic acid and H2O2. Therefore a third-generation electrochemical Mb biosensor based on NiO/GR/CILE was constructed with good stability and reproducibility.

Electrochemical detection of rutin on nitrogen-doped graphene modified carbon ionic liquid electrode

In this paper nitrogen-doped graphene (NG) was synthesized and applied to modify an ionic liquid 1-hexylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE). The fabricated NG/CILE exhibited excellent electrochemical performances. Electrochemical behaviors of rutin on NG/CILE were carefully investigated with a pair of well-defined redox peaks appeared, which was attributed to the presence of NG with electrocatalytic activity. Electrochemical parameters of rutin on NG/CILE were calculated with the values of charge transfer coefficient (α), electron transfer number (n) and electrode reaction standard rate constant (ks) as 0.57, 1.76 and 1.24s−1, respectively. Under the optimal conditions rutin could be detected in the concentration range from 7.0×10−10 to 1.0×10−5mol/L with the detection limit as 0.23nmol/L (3σ) by differential pulse voltammetry. The proposed method was further applied to the determination of rutin tablet samples with satisfactory results.

TRACE DETERMINATION OF GATIFLOXACIN IN PHARMACEUTICAL AND BIOLOGICAL SAMPLES USING HYDROPHOBIC MAGNETIC NANOPARTICLES-ASSISTED IONIC LIQUID MICROEXTRACTION COUPLED WITH SPECTROFLUORIMETRY

A simple and rapid microextraction procedure based on the application of magnetic nanoparticles and hydrophobic 1Hexylpyridinium hexafluorophosphate [Hpy][PF6] ionic liquid (IL) was applied to trace determination of gatifloxacin. A mixture of [Hpy][PF6] and magnetic nanoparticles was injected into the sample solution containing the analyse of interest and a cloudy solution was formed. After centrifuging, the sediment phase containing enriched analyse was determined by spectrofluorimetry. Magnetic nanoparticles used in this microextraction procedure significantly improved the extraction recovery which is due to its proper hydrophobicity. [Hpy][PF6] was used as the extraction solvent due to some physicochemical properties such as high hydrophobicity, water immiscibility and quite viscosity. Under optimum experimental conditions, the proposed method provided a limit of detection (LOD) of 0.09 µg L -1 and a relative standard deviation (R.S.D.) of 3.0%. The present technique was applied to gatifloxacin determination in pharmaceutical formulations and human urine.

Application of poly(acridine orange) and graphene modified carbon/ionic liquid paste electrode for the sensitive electrochemical detection of rutin

A carbon/ionic liquid paste electrode (CILPE) prepared by 1-hexylpyridinium hexafluorophosphate as the binder was used as the substrate electrode. A layer of graphene oxide (GO) film was cast on CILPE surface (GO/CILPE) and the electropolymerization of acridine orange (AO) on electrode was further realized by cyclic voltammetry in the potential range from −1.40V to 1.40V, which could simultaneously reduce GO to graphene (GR) electrochemically. The fabricated PAO-GR/CILPE exhibited good electrochemical performances with higher conductivity and lower electron transfer resistance. Electrochemical behaviors of rutin were further investigated on the modified electrode in 0.1mol/L pH 2.0 phosphate buffer solution by cyclic voltammetry with a pair of well-defined redox peaks appeared. The peak-to-peak separation (ΔEp) was calculated as 0.076V, which proved a fast quasi-reversible electron transfer process and the electrochemical parameters of rutin on PAO-GR/CILPE were calculated. Under the optimal conditions, the linear relationship between the oxidation peak current of rutin and its concentration was obtained in the range from 0.03 to 800.0μmol/L with the detection limit as 8.33nmol/L (3σ). The PAO-GR/CILPE showed good selectivity, stability and reproducibility, which was further applied to detect rutin tablet samples with satisfactory results.

Electrodeposited nanogold decorated graphene modified carbon ionic liquid electrode for the electrochemical myoglobin biosensor

In this paper, a carbon ionic liquid electrode (CILE) was fabricated using ionic liquid 1-hexylpyridinium hexafluorophosphate as modifier, which was further in situ electrodeposited with graphene (GR) and gold nanoparticles step by step to get an Au/GR nanocomposite modified CILE. Myoglobin (Mb) was further immobilized on the Au/GR/CILE surface with Nafion film to get the modified electrode denoted as Nafion/Mb/Au/GR/CILE. Cyclic voltammetric experiments indicated that a pair of well-defined quasi-reversible redox peaks appeared in pH 3.0 phosphate buffer solution with the formal potential (E 0′) located at −0.197 V (vs. saturated calomel electrode), which was the typical characteristics of Mb heme Fe(III)/Fe(II) redox couples. Thus, the direct electron transfer rate between Mb and the modified electrode was promoted due to the high conductivity and increased surface area of Au/GR nanocomposite present on electrode surface. Based on the cyclic voltammetric data, the electrochemical parameters of Mb on the modified electrode were calculated. The Mb-modified electrode showed excellent electrocatalytic activities towards the reduction of trichloroacetic acid and H2O2 with wider linear range and lower detection limit. Using GR and Au nanoparticles modified CILE, a new third-generation electrochemical Mb biosensor was constructed with good stability and reproducibility.

Electrodeposited Graphene and Gold Nanoparticle Modified Carbon Ionic Liquid Electrode for Sensitive Detection of Rutin

Abstract A carbon ionic liquid electrode (CILE) was prepared by using ionic liquid 1-hexylpyridinium hexafluorophosphate (HPPF6) as the binder and the modifier, which was further decorated with gold nanoparticles and graphene (GR) through step by step electrochemical method to get a modified electrode denoted as GR/Au/CILE. Electrochemical performance of GR/Au/CILE was greatly enhanced due to the presence of nano-gold and GR. Different electrochemical methods such as cyclic voltammetry, differential pulse voltammetry and chronocoulometry were used to investigate the electrochemical behaviors of rutin on GR/Au/CILE along with the electrochemical parameters calculated. Under the optimal conditions the oxidation peak current of rutin was proportional to its concentration in the range from 8.0 × 10−8 M to 8.0 × 10−5 M with the detection limit of 2.55 × 10−8 M (3σ). The proposed method was further applied to the rutin tablet samples detection with satisfactory results.

Direct electrochemistry with enhanced electrocatalytic activity of hemoglobin in hybrid modified electrodes composed of graphene and multi-walled carbon nanotubes

A graphene (GR) and multi-walled carbon nanotubes (MWCNT) hybrid was prepared and modified on a 1-hexylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE). Hemoglobin (Hb) was immobilized on GR-MWCNT/CILE surface with Nafion as the film forming material and the modified electrode was denoted as Nafion/Hb-GR-MWCNT/CILE. Spectroscopic results revealed that Hb molecules retained its native structure in the GR-MWCNT hybird. Electrochemical behaviors of Hb were carefully investigated by cyclic voltammetry with a pair of well-defined redox peaks obtained, which indicated that direct electron transfer of Hb was realized in the hybrid modified electrode. The result could be attributed to the synergistic effects of GR-MWCNT hybrid with enlarged surface area and improved conductivity through the formation of a three-dimensional network. Electrochemical parameters of the immobilized Hb on the electrode surface were further calculated with the results of the electron transfer number (n) as 1.03, the charge transfer coefficient (a) as 0.58 and the electron-transfer rate constant (ks) as 0.97s−1. The Hb modified electrode showed good electrocatalytic ability toward the reduction of different substrates such as trichloroacetic acid in the concentration range from 0.05 to 38.0mmolL−1 with a detection limit of 0.0153mmolL−1 (3σ), H2O2 in the concentration range from 0.1 to 516.0mmolL−1 with a detection limit of 34.9nmol/L (3σ) and NaNO2 in the concentration range from 0.5 to 650.0mmolL−1 with a detection limit of 0.282μmolL−1 (3σ). So the proposed electrode had the potential application in the third-generation electrochemical biosensors without mediator.

Optimization of solid-phase extraction based on a new sol-gel material using a response surface methodology for the determination of copper in water samples by flame atomic absorption spectrometry

A simple method for solid-phase extraction and pre-concentration of trace amounts of copper prior to determination by flame atomic absorption spectrometry (FAAS) has been developed. The method is based on the adsorption of Cu(II) ions on a micro-column packed with a sol-gel material doped with 1-hexylpyridinium hexafluorophosphate [C6py+] [] ionic liquid and 8-hydroxyquinoline (oxine) as a novel solid-phase extractor. Different variables affecting the separation/pre-concentration conditions of analyte, including pH of the sample solution, buffer concentration, sample loading flow rate and elution conditions were investigated and optimized utilizing the central composite design (CCD). In the optimum conditions, the limit of detection (LOD), limit of quantification (LOQ) and enrichment factor were 0.5 µg L−1, 1.7 µg L−1 and 50, respectively. The relative standard deviation (RSD) for nine replicate determinations of 25 and 50 µg L−1 Cu were 1.8 and 1.3%, respectively. The calibration graph using the pre-concentration system was linear in the range of 2−120 µg L−1 with a correlation coefficient of 0.9989. A standard reference material (NIST SRM 1566b), was used for validation of the presented method. The optimized method was successfully applied to the determination of copper in several water samples.

Simultaneous electrochemical determination of guanosine and adenosine with graphene–ZrO2 nanocomposite modified carbon ionic liquid electrode

In this paper an ionic liquid 1-hexylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE) was fabricated and used as the basal electrode, which was further modified by graphene (GR) and ZrO2 nanoparticle with chitosan (CTS) film to immobilize the nanocomposite. The modified electrode was denoted as CTS–GR–ZrO2/CILE and further used for the simultaneous detection of adenosine and guanosine. Electrochemical performances of the modified electrode were greatly enhanced due to the presence of GR–ZrO2 nanocomposite, and the direct electro-oxidation behaviors of adenosine and guanosine were carefully investigated. Both adenosine and guanosine exhibited an increase of the oxidation peak currents with the negative shift of the oxidation peak potentials on the modified electrode, which indicated the electrocatalytic activity of GR–ZrO2 nanocomposite on the electrode surface. Electrochemical parameters of adenosine and guanosine on CTS–GR–ZrO2/CILE were calculated respectively, and a new electroanalytical method for the simultaneous determination of adenosine and guanosine was further established with the peak-to-peak separation (ΔEp) as 0.225V. The proposed method was successfully applied to detect adenosine and guanosine in human urine samples with satisfactory results.

Electrodeposited Graphene and Gold Nanoparticle Modified Carbon Ionic Liquid Electrode for Sensitive Detection of Rutin

A carbon ionic liquid electrode (CILE) was prepared by using ionic liquid 1-hexylpyridinium hexafluorophosphate (HPPF6) as the binder and the modifier, and then it was further decorated with gold nanoparticles and graphene (GR) using step by step electrochemical method to get a modified electrode denoted as GR/Au/CILE. Electrochemical performance of GR/Au/CILE was greatly enhanced due to the presence of nano-gold and GR. Different electrochemical methods such as cyclic voltammetry, differential pulse voltammetry and chronocoulometry were used to investigate the electrochemical behaviors of rutin on GR/Au/CILE with the electrochemical parameters calculated. Under the optimal conditions the oxidation peak current of rutin was proportional to its concentration in the range of 8.0 × 10–8-8.0 × 10–5 mol/L with the detection limit of 2.55 × 10–8 mol/L (3σ). The proposed method was applied to the analysis of rutin tablet with satisfactory results.

Sensitive determination of terazosin in pharmaceutical formulations and biological samples by ionic-liquid microextraction prior to spectrofluorimetry.

An efficient and environmentally friendly sample preparation method based on the application of hydrophobic 1-Hexylpyridinium hexafluorophosphate [Hpy][PF6] ionic liquid (IL) as a microextraction solvent was proposed to preconcentrate terazosin. The performance of the microextraction method was improved by introducing a common ion of pyridinium IL into the sample solution. Due to the presence of the common ion, the solubility of IL significantly decreased. As a result, the phase separation successfully occurred even at high ionic strength, and the volume of the settled IL-phase was not influenced by variations in the ionic strength (up to 30% w/v). After preconcentration step, the enriched phase was introduced to the spectrofluorimeter for the determination of terazosin. The obtained results revealed that this system did not suffer from the limitations of that in conventional ionic-liquid microextraction. Under optimum experimental conditions, the proposed method provided a limit of detection (LOD) of 0.027 μg L−1 and a relative standard deviation (R.S.D.) of 2.4%. The present method was successfully applied to terazosin determination in actual pharmaceutical formulations and biological samples. Considering the large variety of ionic liquids, the proposed microextraction method earns many merits, and will present a wide application in the future.

Sol–gel processed pyridinium ionic liquid-modified silica as a new sorbent for separation and quantification of iron in water samples

1-Hexylpyridinium hexafluorophosphate [C6py][PF6] ionic liquid (IL) was firstly used for chemical modification of silica utilizing the acid-catalyzed sol–gel processing. The obtained pyridinium IL-modified silica was employed as a solid phase extraction (SPE) sorbent for removal of trace levels of Fe(III) ions from aqueous samples. The influence of different variables on the separation efficiency, including the concentration of chelating agent, pH, sample flow rate and volume, eluent type, concentration and volume, and interfering ions was investigated by flame atomic absorption spectrometry (FAAS). In the optimum experimental conditions, the limit of detection (3s), limit of quantification (LOQ) and pre-concentration factor were 0.7μgL−1, 2.5μgL−1, and 200, respectively. The relative standard deviation (RSD) for nine replicate determinations of 25μgL−1 Fe was 3.2%. The calibration graph using the pre-concentration system was linear in the range of 2.5–50μgL−1 with a correlation coefficient of 0.9997. The developed method was validated by the analysis of certified reference material and applied successfully to the separation and determination of iron in several water samples.

Determination of cobalt in water samples by atomic absorption spectrometry after pre-concentration with a simple ionic liquid-based dispersive liquid-liquid micro-extraction methodology

Abstract A rapid dispersive liquid-liquid micro-extraction (DLLME) methodology based on the application of 1-hexylpyridinium hexafluorophosphate [C6py][PF6] ionic liquid (IL) as an extractant solvent was applied for the pre-concentration of trace levels of cobalt prior to determination by flame atomic absorption spectrometry (FAAS). 1-Phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) was employed as a chelator forming a Co-PMBP complex to extract cobalt ions from aqueous solution into the fine droplets of [C6py][PF6]. Some effective factors that influence the micro-extraction efficiency include the pH, the PMBP concentration, the amount of ionic liquid, the ionic strength, the temperature and the centrifugation time which were investigated and optimized. In the optimum experimental conditions, the limit of detection (3s) and the enrichment factor were 0.70 µg L−1 and 60, respectively. The relative standard deviation (RSD) for six replicate determinations of 50 µg L−1 Co was 2.36%. The calibration graph using the pre-concentration system was linear at levels 2–166 µg L−1 with a correlation coefficient of 0.9982. The applicability of the proposed method was evaluated by the determination of trace amounts of cobalt in several water samples.

Combination of ionic liquid-based dispersive liquid–liquid micro-extraction with stopped-flow spectrofluorometry for the pre-concentration and determination of aluminum in natural waters, fruit juice and food samples

In this research, we combined ionic liquid-based dispersive liquid-liquid micro-extraction (IL-based DLLME) with stopped-flow spectrofluorometry (SFS) to evaluate the concentration of aluminum in different real samples at trace level. 1-Hexylpyridinium hexafluorophosphate [Hpy][PF(6)] ionic liquid and 8-hydroxyquinoline (oxine), which forms a highly fluorescent complex with Al(3+), were chosen as the extraction solvent and chelating agent, respectively. The hydrophobic Al-oxine complex was extracted into the [Hpy][PF(6)] and separated from the aqueous phase. Then, the concentration of the enriched aluminum in the sediment phase was determined by SFS. Some effective parameters that influence the SFS signals and the micro-extraction efficiency, such as the suction and sending time, the concentration of the chelating agent, pH, the amount of the ionic liquid, the type of disperser solvent and diluting agent, ionic strength, extraction time, equilibration temperature and centrifugation time were investigated and optimized. In the optimum experimental conditions, the limit of detection (3s) and enrichment factor were 0.05microgL(-1) and 100, respectively. The relative standard deviation (RSD) for six replicate determinations of 6microgL(-1) Al was 1.7%. The calibration graph using the pre-concentration system was linear in the range of 0.06-15microgL(-1) with a correlation coefficient of 0.9989. The developed method was validated by the analysis of certified reference materials and applied successfully to the determination of aluminum in several water, fruit juice and food samples.