Water-immiscible Ionic Liquid Research Articles

Ionic Liquid "Water Pocket" for Stable and Environment-Adaptable Aqueous Zinc Metal Batteries.

The strong reactivity of water in aqueous electrolytes toward metallic zinc (Zn), especially at aggressive operating conditions, remains the fundamental obstacle to the commercialization of aqueous zinc metal batteries (AZMBs). Here, a water-immiscible ionic liquid diluent 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)amide (EmimFSI) is reported that can substantially suppress the water activity of aqueous electrolyte by serving as a "water pocket", enveloping the highly active H2 O-dominated Zn2+ solvates and protecting them from parasitic reactions. During Zn deposition, the cation Emim+ and anion FSI- function respectively in mitigating the tip effect and regulating the solid electrolyte interphase (SEI), thereby favoring a smooth Zn deposition layer protected by inorganic species-enriched SEI featuring high uniformity and stability. Combined with the boosted chemical/electrochemical stability endowed by the intrinsic merits of ionic liquid, this ionic liquid-incorporated aqueous electrolyte (IL-AE) enables the stable operation of Zn||Zn0.25 V2 O5 ·nH2 O cells even at a challenging temperature of 60°C (>85% capacity retention over 400 cycles). Finally, as an incidental but practically valuable benefit, the near-zero vapor pressure nature of ionic liquid allows the efficient separation and recovery of high-value components from the spent electrolyte via a mild and green approach, promising the sustainable future of IL-AE in realizing practical AZMBs.

A novel aqueous Li4Fe(CN)6 cathode and hydrophobic ionic liquid electrolyte combined lithium-ion battery

Present study reports an easy and cost-effective method of synthesis of Li4Fe(CN)6 cathode from K4Fe(CN)6.3H2O and LiClO4 in aqueous medium for its use in lithium-ion battery. The synthesized Li4Fe(CN)6 is characterized by UV-Vis, FTIR and cyclic-voltammetry studies. A special laboratory model lithium-ion battery is designed, where aqueous Li4Fe(CN)6 solution acts as a cathode, metallic lithium as anode and 1 molar solution of LiPF6 dissolved in water immiscible ionic liquid, 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6) as electrolyte. The cell exhibits an open circuit potential of 3.12 volt and a good charge-discharge cycling behaviour. The cell delivered a maximum discharge capacity of 86 mAhg-1 (theoretical capacity 112 mAhg-1) at 0.2 C rates with an average discharge potential of 2.1 volts. Although the ionic liquid is a little bit cost intensive, but the easy synthesis methodology with the cheapest raw materials and overall cycling efficiency, makes this technology available as a green economical energy storage device in the current battery industry. Copyright © 2017 VBRI Press.

Comparative evaluation of extraction of tetra- and hexa-valent neptunium ions by CMPO in a room temperature ionic liquid

ABSTRACT Solvent extraction studies were performed to understand the extraction behavior of Np4+ and NpO2 2+ from acidic feeds with CMPO (octyl (phenyl)-N,N-diisobutyl carbamoyl methyl phosphine oxide) dissolved in 1-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide, a water immiscible ionic liquid. Slope analyses on the distribution data revealed the extraction of ML2 type species, where M = Np4+ or NpO2 2+, and L = CMPO. Studies were also carried out with Pu4+ and UO2 2+ under identical conditions. The nature of the extracted species was found to vary with the nature of the ionic species.

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.

The role of ionic liquid [C4 C1 im]Br as an adjuvant on the two-phase formation and the extraction of l-phenylalanine in ABS composed of PEG400 and potassium citrate at different temperatures.

The potential of {polyethylene glycol 400 + potassium citrate} aqueous biphasic system (ABS) with ionic liquid (IL) 1-butyl-3-methylimidazolium bromide ([C4 C1 im]Br) as an adjuvant is examined for the extraction of l-phenylalanine (Phe), as a model biomolecule, at different temperatures and system compositions. The binodal curves and liquid-liquid equilibrium data were determined by the addition of 5 wt% IL to investigate its effect on phase diagrams and Phe partition coefficients. The results indicate that binodal curves of systems with and without IL are more deviated from each other with decreasing temperature. Moreover, IL has a high tendency to partition into the PEG-rich phase. This tendency increases with increasing temperature and system compositions. For Phe, the partition coefficients obtained in this work (KPhe ≈ 5.5-81.2) are significantly higher than those observed in other conventional PEG-inorganic salt ABS (KPhe ≈ 0.5-2.5), water-immiscible ILs two-phase extraction systems (KPhe ≈ 0.02-1.2), or even, in the IL-based ABS with the same IL as the main phase-forming component (KPhe ≈ 3.2). The phase hydrophobicity, salting-out and π⋯π stacking seem to be the main driving forces to affect the extraction aptitude of the studied ABS for Phe. Furthermore, the performance of using [C4 C1 im]Br as adjuvant to improve the partition of Phe in the studied ABS at different temperatures seems to be ruled by the differences in the phases hydrophobicities. Finally, the experimental tie lines and partition coefficients are accurately correlated using the NRTL model. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 2018 © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:1149-1166, 2018.

Comparison of micellar extraction combined with ionic liquid based vortex-assisted liquid–liquid microextraction and modified quick, easy, cheap, effective, rugged, and safe method for the determination of difenoconazole in cowpea

Two simple sample pretreatment for the determination of difenoconazole in cowpea was developed including micellar extraction combined with ionic liquid based vortex-assisted liquid–liquid microextraction (ME-IL-VALLME) prior to high performance liquid chromatography (HPLC), and modified quick, easy, cheap, effective, rugged, and safe method (QuEChERS) coupled with HPLC–MS/MS. In ME-IL-VALLME method, the target analyte was extracted by surfactant Tween 20 micellar solution, then the supernatant was diluted with 3mL water to decrease the solubility of micellar solution. Subsequently, the vortex-assisted liquid–liquid microextraction (VALLME) procedure was performed in the diluted extraction solution by using the ionic liquid of 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM]PF6) as the extraction solvent and Tween 20 as an emulsifier to enhance the dispersion of the water-immiscible ionic liquid into the aqueous phase. Parameters that affect the extraction have been investigated in both methods Under the optimum conditions, the limits of quantitation were 0.10 and 0.05mgkg−1, respectively. And good linearity was achieved with the correlation coefficient higher than 0.9941. The relative recoveries ranged from 78.6 to 94.8% and 92.0 to 118.0% with the relative standard deviations (RSD) of 7.9–9.6% and 1.2–3.2%, respectively. Both methods were quick, simple and inexpensive. However, the ME-IL-VALLME method provides higher enrichment factor compared with conventional QuEChERS method. The ME-IL-VALLME method has a strong potential for the determination of difenoconazole in complex vegetable matrices with HPLC.

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

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. 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. 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.

A Fast and Efficient Replacement of CTAB with MUA on the Surface of Gold Nanorods Assisted by a Water-Immiscible Ionic Liquid.

The synthesis and surface modification of gold nanorods (GNRs) is one of the most important and basic issues in nanoscience. Most of the widely investigated GNRs are coated with a cetyltrimethylammonium bromide(CTAB) bilayer. Here, a highly efficient method is proposed to replace CTAB from the surface of GNRs with a bifunctional 11-mercaptoundecanoic acid in order to decrease the possible toxicity caused by CTAB. This ligand exchange is achieved in a biphasic mixture of an aqueous solution and a water-immiscible ionic liquid (IL), [BMIM][Tf2 N]. That is, by mixing IL, mercaptoundecanoic acid (MUA)/IL (200 × 10-3 m) and a concentrated aqueous solution of GNRs together, followed by vortex stirring for 90 s, CTAB-capped GNRs with varying aspect ratios can be turned into corresponding MUA-capped GNRs with the same aspect ratio. Furthermore, the formed MUA-capped GNRs can be obtained in a large quantity and stored as powders for easy use. The MUA-capped GNRs with improved biocompatibility and colloidal stability are well suited for further biological functionalization and potential applications. This IL-assisted ligand exchange can reverse the surface charge, enhance the stability of GNRs, and suppress its cytotoxicity.

Phase transfer of TiO2 nanoparticles from water to ionic liquid triggered by phosphonic acid grafting.

Controlling the interface between TiO2 nanocrystals and ionic liquids is of high fundamental and applied interest for energy storage and conversion devices. Phase transfer of nanoparticles from a synthesis medium to a processing or an application medium plays a significant role in nanotechnology. Here we demonstrate that surface modification with phosphonic acids bearing cationic end-groups can trigger the phase transfer of TiO2 nanoparticles from an aqueous sol to a typical water-immiscible ionic liquid, [Emim][NTf2]. The transfer involves both the grafting of the phosphonic acid moiety and the exchange of the counter ion of the cationic end-group by NTf2 anions, as demonstrated by solid-state NMR, elemental analysis and independent grafting and ion exchange experiments. Furthermore, the colloidal stability of the TiO2 sols in [Emim][NTf2] strongly depends on the hydrophobic character of the cationic end-groups.

The method of appearing solvent: Extraction of metal ions from aqueous solutions into in situ forming ionic liquid

The simultaneous dissolution of tetraoctylammonium bromide and sodium N-lauroyl sarcosinate in water leads to the in situ formation of a water-immiscible ionic liquid, tetraoctylammonium N-lauroyl sarcosinate. The new phase formed can extract cadmium, cobalt, copper, nickel, lead, and zinc ions from aqueous solution in the presence of 4-(2-pyridylazo)resorcinol (PAR), while it can extract cadmium ions in the absence of PAR.

Combination of deep eutectic solvent and ionic liquid to improve biocatalytic reduction of 2-octanone with Acetobacter pasteurianus GIM1.158 cell.

The efficient anti-Prelog asymmetric reduction of 2-octanone with Acetobacter pasteurianus GIM1.158 cells was successfully performed in a biphasic system consisting of deep eutectic solvent (DES) and water-immiscible ionic liquid (IL). Various DESs exerted different effects on the synthesis of (R)-2-octanol. Choline chloride/ethylene glycol (ChCl/EG) exhibited good biocompatibility and could moderately increase the cell membrane permeability thus leading to the better results. Adding ChCl/EG increased the optimal substrate concentration from 40 mM to 60 mM and the product e.e. kept above 99.9%. To further improve the reaction efficiency, water-immiscible ILs were introduced to the reaction system and an enhanced substrate concentration (1.5 M) was observed with C4MIM·PF6. Additionally, the cells manifested good operational stability in the reaction system. Thus, the efficient biocatalytic process with ChCl/EG and C4MIM·PF6 was promising for efficient synthesis of (R)-2-octanol.

Non-water miscible ionic liquid improves biocatalytic production of geranyl glucoside with Escherichia coli overexpressing a glucosyltransferase

Whole cells of Escherichia coli overexpressing a glucosyltransferase from Vitis vinifera were used for the glucosylation of geraniol to geranyl glucoside. A high cell density cultivation process for the production of whole-cell biocatalysts was developed, gaining a dry cell mass concentration of up to 67.6±1.2gL(-1) and a glucosyltransferase concentration of up to 2.7±0.1g protein L(-1) within a process time of 48h. Whole-cell batch biotransformations in milliliter-scale stirred-tank bioreactors showed highest conversion of geraniol at pH 7.0 although the pH optimum of the purified glucosyltransferase was at pH 8.5. The biocatalytic batch process performance was improved significantly by the addition of a water-immiscible ionic liquid (N-hexylpyridinium bis(trifluoromethylsulfonyl)imid) for in situ substrate supply. The so far highest final geranyl glucoside concentration (291±9mgL(-1)) and conversion (71±2%) reported for whole-cell biotransformations of geraniol were achieved with 5% (v/v) of the ionic liquid.

Mercury determination in urine samples by gold nanostructured screen-printed carbon electrodes after vortex-assisted ionic liquid dispersive liquid–liquid microextraction

A novel approach is presented to determine mercury in urine samples, employing vortex-assisted ionic liquid dispersive liquid–liquid microextraction and microvolume back-extraction to prepare samples, and screen-printed electrodes modified with gold nanoparticles for voltammetric analysis. Mercury was extracted directly from non-digested urine samples in a water-immiscible ionic liquid, being back-extracted into an acidic aqueous solution. Subsequently, it was determined using gold nanoparticle-modified screen-printed electrodes. Under optimized microextraction conditions, standard addition calibration was applied to urine samples containing 5, 10 and 15 μg L−1 of mercury. Standard addition calibration curves using standards between 0 and 20 μg L−1 gave a high level of linearity with correlation coefficients ranging from 0.990 to 0.999 (N = 5). The limit of detection was empirical and statistically evaluated, obtaining values that ranged from 0.5 to 1.5 μg L−1, and from 1.1 to 1.3 μg L−1, respectively, which are significantly lower than the threshold level established by the World Health Organization for normal mercury content in urine (i.e., 10–20 μg L−1). A certified reference material (REC-8848/Level II) was analyzed to assess method accuracy finding 87% and 3 μg L−1 as the recovery (trueness) and standard deviation values, respectively. Finally, the method was used to analyze spiked urine samples, obtaining good agreement between spiked and found concentrations (recovery ranged from 97 to 100%).

Efficient antimicrobial activity and reduced toxicity of 1-dodecyl-3-methylimidazolium tetrafluoroborate ionic liquid/β-cyclodextrin complex

Water immiscible ionic liquid 1-dodecyl-3-methylimidazolium tetrafluoroborate (DMIM-BF4) and its inclusion complex with β-cyclodextrin (β-CD) in molar ratio 1:1 have been synthesized. The formation of DMIM-BF4/β-CD complex was confirmed by FT-IR analysis, 1H NMR analysis, and differential scanning calorimetry data. Our results indicate that the aliphatic tail of DMIM-BF4 is included into β-CD inner cavity whereas imidazolium ring is located outside the torus. Moreover, the weak interaction between polar components of ionic liquid and hydrophilic outer surface of β-CD has also been detected. The standard agar disk diffusion method was performed to evaluate antimicrobial efficiency of the obtained compounds against Staphylococcus aureus (ATCC-25923), Escherichia coli (ATCC-25922) and Pseudomonas aeruginosa (ATCC-27853), Candida albicans (M 885 ATCC 10231) and its clinical isolate test-cultures. It has been found that both DMIM-BF4 and DMIM-BF4/β-CD complex possess high antimicrobial activity as revealed by similar zone inhibition values against all tested microorganisms. The acute toxicity studies on Danio rerio (zebrafish) model organism showed that the pure ionic liquid DMIM-BF4 is slightly toxic compound having LD50 value of 7mg/L, whereas DMIM-BF4/β-CD complex has considerably reduced toxicity (LD50=100mg/L) and therefore have potentially wider application areas.

Multiple response optimization of sequential speciation of chromium in water samples by in situ solvent formation dispersive liquid–liquid microextraction prior to electrothermal atomic absorption spectrometry determination

A sensitive and selective in situ solvent formation dispersive liquid–liquid microextraction (in situ DLLME) method followed by electrothermal atomic absorption spectrophotometry for sequential extraction and determination of trace level of chromium (Cr) species was developed. The preconcentration and extraction of Cr species were carried out using ammonium pyrrolidine dithiocarbamate as a chelating agent, and a water-immiscible ionic liquid based on in situ solvent formation as an extraction solvent. Various operating variables such as sample pH, the KPF6 amount and the ionic liquid volume on the extraction efficiency responses (EE%) of Cr(III) and Cr(VI) ions were investigated. Response surface methodology using central composite design was employed for modeling of the responses. Multi-response optimization with desirability function (DF) approach has been used to maximize EE% one Cr species in the presence of another species. After this step, DF was employed to optimize the variables to define the best extraction conditions for Cr speciation. Under the optimal extraction conditions, the calibration curves were linear in the concentration ranges of 20–200 ng L−1 for Cr(III) and 70–250 ng L−1 for Cr(VI) with the limit of detections of 3.7 ng L−1 for Cr(III) and 2.13 ng L−1 for Cr(VI). The relative standard deviations of five microextractions of 100 ng L−1 Cr(III) and Cr(VI) were 9.07 % and 2.39 %, respectively. Finally, the developed method was applied to the determination of Cr(III) and Cr(VI) ions in real water samples.

In situ emulsification microextraction using a dicationic ionic liquid followed by magnetic assisted physisorption for determination of lead prior to micro-sampling flame atomic absorption spectrometry

For the first time, a simple and efficient in situ emulsification microextraction method using a dicationic ionic liquid followed by magnetic assisted physisorption was presented to determine trace amounts of lead. In this method, 400 μL of 1.0 mol L−1 lithium bis (trifluoromethylsulfonyl) imide aqueous solution, Li[NTf2], was added into the sample solution containing 100 μL of 1.0 mol L−1 1,3-(propyl-1,3-diyl) bis (3-methylimidazolium) chloride, [pbmim]Cl2, to form a water immiscible ionic liquid, [pbmim][NTf2]2. This new in situ formed dicationic ionic liquid was applied as the acceptor phase to extract the lead-ammonium pyrrolidinedithiocarbamate (Pb-APDC) complexes from the sample solution. Subsequently, 30 mg of Fe3O4 magnetic nanoparticles (MNPs) were added into the sample solution to collect the fine droplets of [pbmim][NTf2]2, physisorptively. Finally, MNPs were eluted by acetonitrile, separated by an external magnetic field and the obtained eluent was subjected to micro-sampling flame atomic absorption spectrometry (FAAS) for further analysis. Comparing with other microextraction methods, no special devices and centrifugation step are required. Parameters influencing the extraction efficiency such as extraction time, pH, concentration of chelating agent, amount of MNPs and coexisting interferences were studied. Under the optimized conditions, this method showed high extraction recovery of 93% with low LOD of 0.7 μg L−1. Good linearity was obtained in the range of 2.5–150 μg L−1 with determination coefficient (r2) of 0.9921. Relative standard deviation (RSD%) for seven repeated measurements at the concentration of 10 μg L−1 was 4.1%. Finally, this method was successfully applied for determination of lead in some water and plant samples.

Ionic liquid-functionalized crystals of barium sulfate: A hybrid organic–inorganic material with tuned hydrophilicity and solid–liquid behavior

A hybrid organic–inorganic material composed of barium sulfate (BaSO4) crystals embedded within a hydrophobic ionic liquid (ILs) matrix has been synthesized. The contact between the inorganic solid and the organic coating is created by chemical interactions between the crystal surface and the ionic liquid. The material exhibits higher affinity to lipophilic media than the non-modified BaSO4. Increased hydrophobicity is a property often sought for inorganic particles to be applied in non-polar formulations. Immobilization of water-immiscible ILs on a hydrophilic solid carrier enables their application in aqueous solutions and the creation of appreciable hydrophobic-IL/water interfaces on the dispersion of solid-like material in aqueous media.

In situ ionic liquid dispersive liquid–liquid microextraction and determination of Au(III) by flame atomic absorption spectrometry

A simple, rapid, selective in situ ionic liquid dispersive liquid–liquid microextraction and determination of Au(III) by flame atomic absorption spectrometry has been first proposed for the extraction of Au(III). In the developed method, NH4PF6 aqueous solution was added to the sample solution containing [CnMIM]Br to form a water-immiscible ionic liquid, [CnMIM]PF6 as extraction solution. The formation of hydrophobic ionic liquid and subsequent extraction of gold(III) were achieved in one step without the need for dispersive solvent and chelating agent. The effects of various experimental parameters on gold extraction were investigated in detail. At optimum conditions, the linear range of 0.9–400 ng/mL of Au(III), the limit of detection 0.13 ng/mL for Au(III) along with enrichment factors of 23.7 and the extraction capacity of 97.5 mg/g by the proposed method for Au(III) were obtained. The proposed method was applied to extract trace amounts of Au(III) in water samples with satisfactory results.

Ionic-liquid-based, manual-shaking- and ultrasound-assisted, surfactant-enhanced emulsification microextraction for the determination of three fungicide residues in juice samples

A novel manual-shaking- and ultrasound-assisted surfactant-enhanced emulsification microextraction method was developed for the determination of three fungicides in juice samples. In this method, the ionic liquid, 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, instead of a volatile organic solvent was used as the extraction solvent. The surfactant, NP-10, was used as an emulsifier to enhance the dispersion of the water-immiscible ionic liquid into an aqueous phase, which accelerated the mass transfer of the analytes. Organic dispersive solvent typically required in common dispersive liquid-liquid microextraction methods was not necessary. In addition, manual shaking for 15 s before ultrasound to preliminarily mix the extraction solvent and the aqueous sample could greatly shorten the time for dispersing the ionic liquid into aqueous solution by ultrasound irradiation. Several experimental parameters affecting the extraction efficiency, including type and volume of extraction solvent, type and concentration of surfactant, extraction time, and pH, were optimized. Under the optimized conditions, good linearity with the correlation coefficients (γ) higher than 0.9986 and high sensitivity with the limit of detection ranging from 0.4 to 1.6 μg/L were obtained. The average recoveries ranged from 61.4 to 86.0% for spiked juice, with relative standard deviations from 1.8 to 9.7%. The proposed method was demonstrated to be a simple, fast, and efficient method for the analysis of the target fungicides in juice samples.

Simultaneous multicomponent spectrophotometric monitoring of methyl and propyl parabens using multivariate statistical methods after their preconcentration by robust ionic liquid-based dispersive liquid–liquid microextraction

A powerful and efficient signal-preprocessing technique that combines local and multiscale properties of the wavelet prism with the global filtering capability of orthogonal signal correction (OSC) is applied for pretreatment of spectroscopic data of parabens as model compounds after their preconcentration by robust ionic liquid-based dispersive liquid–liquid microextraction method (IL-DLLME). In the proposed technique, a mixture of a water-immiscible ionic liquid (as extraction solvent) [Hmim][PF6] and disperser solvent is injected into an aqueous sample solution containing one of the IL’s ions, NaPF6, as extraction solvent and common ion source. After preconcentration, the absorbance of the extracted compounds was measured in the wavelength range of 200–700nm. The wavelet orthogonal signal correction with partial least squares (WOSC-PLS) method was then applied for simultaneous determination of each individual compound. Effective parameters, such as amount of IL, volume of the disperser solvent and amount of NaPF6, were inspected by central composite design to identify the most important parameters and their interactions. The effect of pH on the sensitivity and selectivity was studied according to the net analyte signal (NAS) for each component. Under optimum conditions, enrichment factors of the studied compounds were 75 for methyl paraben (MP) and 71 for propyl paraben (PP). Limits of detection for MP and PP were 4.2 and 4.8ngmL−1, respectively. The root mean square errors of prediction for MP and PP were 0.1046 and 0.1275μgmL−1, respectively. The practical applicability of the developed method was examined using hygienic, cosmetic, pharmaceutical and natural water samples.