Application of ionic liquids based microwave-assisted extraction of three alkaloids N-nornuciferine, O-nornuciferine, and nuciferine from lotus leaf

The application of ionic liquids based microwave-assisted extraction (ILMAE) was successfully developed for extracting three alkaloids N-nornuciferine, O-nornuciferine, and nuciferine from lotus leaf. Seven kinds of 1-alkyl-3-methylimidazolium with different cations and anions were investigated in this work and 1.0 M 1-hexyl-3-methylimidazolium bromide ([C₆MIM]Br) solution was selected as solvent. In addition, the microwave parameters including irradiation power, extraction time and solid-liquid ratio were optimized. Compared with the regular MAE and conventional heat-reflux extraction (HRE), the proposed approach exhibited higher efficiency (0.9-43.7% enhanced) and shorter extraction time (from 2 h to 2 min), which indicated ILMAE was an efficient, rapid and simple sample preparation technique. Moreover, the proposed method was validated by the linearity, reproducibility, and recovery experiments. Good linearity was observed with the regression coefficients (r²) between 0.9998 and 0.9999. The recoveries of all methods were in the range of 94.6% and 105.5% with RSD lower than 6.6%, which indicated that the proposed method was credible.     

Ionic liquids extraction of Para Red and Sudan dyes from chilli powder, chilli oil and food additive combined with high performance liquid chromatography

A simple analytical method, based on the coupling of ionic liquid-based extraction with high performance liquid chromatography (HPLC), is developed for the determination of Sudan dyes (I, II, III and IV) and Para Red in chilli powder, chilli oil and food additive samples. Two ionic liquids (ILs), 1-butyl-3-methylimidazolium hexafluorophosphate ([C₄mim][PF₆]) and 1-octyl-3-methylimidazolium hexafluorophosphate ([C₈mim][PF₆]), were compared as extraction solvents; experiments indicated that the latter possesses higher recoveries for each analyte. Parameters related to extraction of Sudan dyes and Para Red were also optimized. Under the optimal conditions, good reproducibility of extraction performance was obtained, with the relative standard deviation (RSD) values ranging from 2.0% to 3.5%. The detection limits of Sudan dyes and Para Red (LOD, S/N = 3) were in the range of 7.0-8.2 μg kg⁻¹ for chilli powder and 11.2-13.2 μg L⁻¹ for chilli oil and food additive. The recoveries were in the range of 76.8-109.5% for chilli powder samples and 70.7-107.8% for chilli oil and food additive samples.     

Ionic liquid-based microwave-assisted extraction of phenolic alkaloids from the medicinal plant Nelumbo nucifera Gaertn

An ionic liquid-based microwave-assisted extraction (ILMAE) approach has been successfully applied to the effective extraction of the phenolic alkaloids present in samples of the medicinal plant Nelumbo nucifera Gaertn. The ionic liquids investigated comprised a range of four anions, four 1-alkyl-3-methylimidazolium derivatives differing in hydrophobic chain length. The results indicate that varying the anion has apparent effects on the overall extraction efficiency. In addition, the influence of some microwave parameters, such as irradiation power, extraction time and solid-liquid ratio, are also investigated. Under the optimized conditions, the proposed approach has been evaluated in comparison with the conventional heat-reflux extraction (HRE) and regular MAE. The reduction of the extraction times (from 2h to 90s) and remarkable higher efficiency (20-50% improved) supports the suitability of the proposed approach. In addition, the proposed method is validated by the recovery, correlation coefficient (R(2)), and reproducibility (RSD, n=5), which are in the range of 98-105%, 0.9994-0.9998, and 1.2-5.4%, respectively.     

Extraction and isolation of flavonoid glycosides from Flos Sophorae Immaturus using ultrasonic‐assisted extraction followed by high‐speed countercurrent chromatography

A method of ultrasonic‐assisted extraction followed by high‐speed countercurrent chromatography was established for the extraction and isolation of three flavonoid glycosides, i.e. rutin, narcissin, and nicotiflorin from Flos Sophorae Immaturus. The effects of ultrasonic‐assisted extraction factors for the main flavonoid compound (rutin) from Flos Sophorae Immaturus were optimized using Box–Behnken design combined with response surface methodology. The optimum conditions were determined as ultrasonic power 83% (600 W), solvent‐to‐material ratio 56:1, methanol concentration 82% v/v, and extraction time 60 min. Three bioactive flavonol glucosides, rutin, narcissin, and nicotiflorin were isolated from Flos Sophorae Immaturus using high‐speed countercurrent chromatography. The separation was performed with a two‐phase solvent system containing ethyl acetate/n‐butanol/methanol/water (4:0.9:0.2:5, v/v). Amounts of 87 mg of rutin, 10.8 mg of narcissin, and 1.8 mg of nicotiflorin were isolated from 302 mg of crude extract of Flos Sophorae Immaturus in a one‐step separation within 160 min with purities of 99.3, 98.0, and 95.1%, respectively, as determined by HPLC with diode array detection. Their structures were characterized by UV, MS, and NMR spectroscopy. It was demonstrated that the established method was simple, fast, and convenient, which was feasible to extract and isolate active flavonoid glycosides from Flos Sophorae Immaturus.     

Ionic liquid‐based microwave‐assisted extraction for the determination of flavonoid glycosides in pigeon pea leaves by high‐performance liquid chromatography‐diode array detector with pentafluorophenyl column

In this study, an ionic liquid‐based microwave‐assisted extraction (ILMAE) followed by high‐performance liquid chromatograph y ‐diode array detector with a pentafluorophenyl column for the extraction and quantification of eight flavonoid glycosides in pigeon pea leaves is described. Compared with conventional extraction methods, ILMAE is a more effective and environment friendly method for the extraction of nature compounds from herbal plants. Nine different types of ionic liquids with different cations and anions were investigated. The results suggested that varying the anion and cation had significant effects on the extraction of flavonoid glycosides, and 1.0 M 1‐butyl‐3‐methylimidazolium bromide ([C4MIM]Br) solution was selected as solvent. In addition, the extraction procedures were also optimized using a series of single‐factor experiments. The optimum parameters were obtained as follows: extraction temperature 60°C, liquid–solid ratio 20:1 mL/g and extraction time 13 min. Moreover, an HPLC method using pentafluorophenyl column was established and validated. Good linearity was observed with the regression coefficients (r²) more than 0.999. The limit of detection (LODs) (S/N = 3) and limit of quantification (LOQs) (S/N = 10) for the components were less than 0.41 and 1.47 μg/mL, respectively. The inter‐ and intraday precisions that were used to evaluate the reproducibility and relative standard deviation (RSD) values were less than 4.57%. The recoveries were between 97.26 and 102.69%. The method was successfully used for the analysis of samples of pigeon pea leaves. In conclusion, the developed ILMAE‐HPLC‐diode array detector using pentafluorophenyl column method can be applied for quality control of pigeon pea leaves and related medicinal products.     

Ionic liquid-based microwave-assisted extraction of essential oil and biphenyl cyclooctene lignans from Schisandra chinensis Baill fruits

Ionic liquid-based microwave-assisted extraction (ILMAE) has been successfully applied in extracting essential oil and four kinds of biphenyl cyclooctene lignans from Schisandra chinensis Baill. 0.25 M 1-lauryl-3-methylimidazolium bromide ionic liquid is selected as solvent. The optimum parameters of dealing with 25.0 g sample are 385 W irradiation power, 40 min microwave extraction time and 1:12 solid-liquid ratio. The yields of essential oil and lignans are 12.12±0.37 ml/kg and 250.2±38.2 mg/kg under the optimum conditions. The composition of the essential oil extracted by hydro-distillation, steam-distillation and ILMAE is analyzed by GC-MS. With ILMAE method, the energy consumption time has not only been shortened to 40 min (hydro-distillation 3.0 h for extracting essential oil and reflux extraction 4.0 h for extracting lignans, respectively), but also the extraction efficiency has been improved (extraction of lignans and distillation of essential oil at the same time) and reduces the environmental pollution. S. chinensis materials treated by different methods are observed by scanning electronic microscopy. Micrographs provide more evidence to prove that ILMAE is a better and faster method. The experimental results also indicate that ILMAE is a simple and efficient technique for sample preparation.     

Ultrasonication-assisted extraction and preconcentration of medicinal products from herb by ionic liquids

Ionic liquid-based extraction of medicinal or useful compounds from plants was investigated as an alternative to supercritical fluid, cloud point and conventional organic solvent extractions. The method integrated extraction and preconcentration. Medicinal products were first extracted by an ionic liquid solution, part of which was then converted to a hydrophobic form by anion metathesis for preconcentration. The remaining soluble ionic liquid acted as a dispersive agent to enhance the efficiency of preconcentration. Protein in the extract was precipitated spontaneously without addition of further solvents. Ultrasonication assisted this method for extraction and preconcentration of cryptotanshinone, tanshinone I and tanshinone II A from Salvia Miltiorrhiza Bunge. 0.233 mg g⁻¹, 0.695 mg g⁻¹ and 0.682 mg g⁻¹ of each, respectively, were extracted using [OMIM][Cl], and preconcentrated in a [OMIM][PF₆] phase at respective concentrations of 148.1, 507.1 and 486.1 μg mL⁻¹. The method exhibited potential applicability with other medicinal products.     

Glycolysis of poly(ethylene terephthalate) (PET) using basic ionic liquids as catalysts

The glycolysis of poly(ethylene terephthalate) (PET) was studied using several ionic liquids and basic ionic liquids as catalysts. The basic ionic liquid, 1-butyl-3-methylimidazolium hydroxyl ([Bmim]OH), exhibits higher catalytic activity for the glycolysis of PET, compared with 1-butyl-3-methylimidazolium bicarbonate ([Bmim]HCO₃), 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) and 1-butyl-3-methylimidazolium bromide ([Bmim]Br). FT-IR, ¹H NMR and DSC were used to confirm the main product of glycolysis was bis(2-hydroxyethyl) terephthalate (BHET) monomer. The influences of experimental parameters, such as the amount of catalyst, glycolysis time, reaction temperature, and dosages of ethylene glycol on the conversion of PET, yield of BHET were investigated. The results showed a strong influence of the mixture evolution of temperature and reaction time on depolymerization of PET. Under the optimum conditions of m(PET):m(EG): 1:10, dosage of [Bmim]OH at 0.1 g (5 wt%), reaction temperature 190 °C and time 2 h, the conversion of PET and the yield of BHET were 100% and 71.2% respectively. Balance between the polymerization of BHET and depolymerization of PET could be changed when the reaction time was more than 2 h and contents of catalyst and EG were changed.     

Effect of the polarity of silver nanoparticles induced by ionic liquids on facilitated transport for the separation of propylene/propane mixtures

The effect of ionic liquids on the formation of a partial positive charge on the surface of silver nanoparticle and its subsequent effect on facilitated olefin transport were investigated. Three different ionic liquids of 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM⁺BF₄⁻), 1-butyl-3-methylimidazolium triflate (BMIM⁺Tf⁻), and 1-butyl-3-methylimidazolium nitrate (BMIM⁺NO₃⁻) were employed to control the positive charge density of the surface of silver nanoparticles. The positive charge density of the silver nanoparticles, as characterized by the binding energy of the silver atom, was in the following order: BMIM⁺BF₄⁻/Ag ? BMIM⁺Tf⁻/Ag > BMIM⁺NO₃⁻/Ag. This order was consistent with the tendency of ionic liquids to form free ions. The best separation performance for the propylene/propane mixtures was a mixed gas selectivity of 17 and a permeance of 7 GPU through a composite membrane consisting of BMIM⁺BF₄⁻/Ag. A better separation performance for olefin/paraffin mixtures was observed with a higher positive charge density of the silver nanoparticles. It was therefore concluded that facilitated olefin transport was a direct consequence of the surface positive charge of the silver nanoparticles induced by ionic liquids.     

Preparation of magnetic molecularly imprinted polymers for separating rutin from Chinese medicinal plants

The preparation of magnetic molecularly imprinted polymers (MMIPs) which can be used for the separation and purification of rutin from Chinese medicinal plants has been proposed. By applying the improved co-precipitation method, magnetic Fe(3)O(4) particles were easily prepared, followed by the modification of TEOS and functionalization with -CH=CH(2). Using functionalized Fe(3)O(4) particles as the magnetic cores, rutin as the template, and acrylamide as the functional monomer, MMIPs were synthesized by surface-imprinted polymerization under the protection of nitrogen gas and successive mechanical stirring at 60 °C for 24 h. Magnetic non-molecularly imprinted polymers (MNIPs) were also prepared with the same synthesis procedure as with MMIPs only without the presence of rutin. Magnetic particles were characterized by FT-IR, XRD, and TG analysis. And the selectivity of MMIPs was also investigated in detail. In addition, the performance of the MMIPs for the adsorption of rutin in the analysis of Chinese medicinal plants was assessed. The mean recoveries were 84.33% (RSD: 3.22%, n = 3) for Saururus chinensis (Lour.) Bail and 85.20% (RSD: 3.58%, n = 3) for Flos Sophorae, respectively, which showed that the prepared MMIPs with many advantages possess the value of practical application.     

Determination of chlorophenols in landfill leachate using headspace sampling with ionic liquid-coated solid-phase microextraction fibers combined with gas chromatography–mass spectrometry

A new microextraction technique based on ionic liquid solid-phase microextraction (IL-SPME) was developed for determination of trace chlorophenols (CPs) in landfill leachate. The synthesized ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([C₄MIM][PF₆]), was coated onto the spent fiber of SPME for extraction of trace CPs. After extraction, the absorbed analytes were desorbed and quantified using gas chromatography–mass spectrometry (GC/MS). The term of the proposed method is as ionic liquid-coated of solid-phase microextraction combined with gas chromatography–mass spectrometry (IL-SPME-GC/MS). No carryover effect was found, and every laboratory-made ionic liquids-coated-fiber could be used for extraction at least eighty times without degradation of efficiency. The chlorophenols studied were 2,4-dichlorophenol (2,4-DP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP), and pentachlorophenol (PCP). The best results of chlorophenols analysis were obtained with landfill leachate at pH 2, headspace extraction for 4 min, and thermal desorption with the gas chromatograph injector at 240 °C for 4 min. Linearity was observed from 0.1 to 1000 μg L⁻¹ with relative standard deviations (RSD) less than 7% and recoveries were over 87%. The limit of detection (LOD) for pentachlorophenol was 0.008 μg L⁻¹. The proposed method was tested by analyzing landfill leachate from a sewage farm. The concentrations of chlorophenols were detected to range from 1.1 to 1.4 μg L⁻¹. The results demonstrate that the IL-SPME-GC/MS method is highly effective in analyzing trace chlorophenols in landfill leachate.     

Enzyme-assisted extraction and ionic liquid-based dispersive liquid–liquid microextraction followed by high-performance liquid chromatography for determination of patulin in apple juice and method optimization using central composite design

A simple and highly sensitive analytical methodology for isolation and determination of patulin in apple-juice samples, based on enzyme-assisted extraction (EAE) and ionic liquid-based dispersive liquid–liquid microextraction (IL-DLLME) was developed and optimized. Enzymes play essential roles in eliminating interference and increasing the extraction efficiency of patulin. Apple-juice samples were treated with pectinase and amylase. A mixture of 80 μL ionic liquid and 600 μL methanol (disperser solvent) was used for the IL-DLLME process. The sedimented phase was analyzed by high-performance liquid chromatography (HPLC). Experimental parameters controlling the performance of DLLME, were optimized using response surface methodology (RSM) based on central composite design (CCD). Under optimum conditions, the calibration curves showed high levels of linearity (R² > 0.99) for patulin in the range of 1–200 ng g⁻¹. The relative standard deviation (RSD) for the seven analyses was 7.5%. The limits of detection (LOD) and limits of quantification (LOQ) were 0.15 ng g⁻¹ and 0.5 ng g⁻¹, respectively. The merit figures, compared with other methods, showed that new proposed method is an accurate, precise and reliable sample-pretreatment method that substantially reduces sample matrix interference and gives very good enrichment factors and detection limits for investigation trace amount of patulin in apple-juice samples.     

Ionic liquid-based single drop microextraction combined with electrothermal atomic absorption spectrometry for the determination of manganese in water samples

Room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate [C₄MIM][PF₆], was used as an alternative to volatile organic solvents in single drop microextraction-electrothermal atomic absorption spectrometry (SDME-ETAAS). Manganese was extracted from aqueous solution into a drop of the ionic liquid after complextaion with 1-(2-thiazolylazo)-2-naphthol (TAN) and the drop was directly injected into the graphite furnace. Several variables affecting microextraction efficiency and ETAAS signal, such as pyrolysis and atomization temperature, pH, TAN concentration, extraction time, drop volume and stirring rate were investigated and optimized. In the optimum experimental conditions, the limit of detection (3 s) and the enhancement factor were 0.024 μg L⁻¹ and 30.3, respectively. The relative standard deviation (RSD) for five replicate determinations of 0.5 μg L⁻¹ Mn(II) was 5.5%. The developed method was validated by the analysis of a certified reference material (NIST SRM 1643e) and applied successfully to the determination of manganese in several natural water samples.     

On-line ionic liquid-based preconcentration system coupled to flame atomic absorption spectrometry for trace cadmium determination in plastic food packaging materials

A novel on-line preconcentration method based on liquid-liquid (L-L) extraction with room temperature ionic liquids (RTILs) coupled to flame atomic absorption spectrometry (FAAS) was developed for cadmium determination in plastic food packaging materials. The methodology is based on the complexation of Cd with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) reagent after sample digestion followed by extraction of the complex with the RTIL 1-butyl-3-methylimidazolium hexafluorophosphate ([C₄mim][PF₆]). The mixture was loaded into a flow injection analysis (FIA) manifold and the RTIL rich-phase was retained in a microcolumn filled with silica gel. The RTIL rich-phase was then eluted directly into FAAS. A enhancement factor of 35 was achieved with 20 mL of sample. The limit of detection (LOD), obtained as IUPAC recommendation, was 6 ng g⁻¹ and the relative standard deviation (R.S.D.) for 10 replicates at 10 μg L⁻¹ Cd concentration level was 3.9%, calculated at the peak heights. The calibration graph was linear and a correlation coefficient of 0.9998 was achieved. The accuracy of the method was evaluated by both a recovery study and comparison of results with direct determination by electrothermal atomic absorption spectrometry (ETAAS). The method was successfully applied for Cd determination in plastic food packaging materials and Cd concentrations found were in the range of 0.04-10.4 μg g⁻¹.     

Chloride based ionic liquids as promoting agents for Meerwein reaction in solventless conditions

Chloride based ionic liquids were used as chloride source in Meerwein reaction either in [bmim]X (bmim = 1-butyl-3-methylimidazolium, X = BF₄, PF₆) as solvents or in solventless conditions. Satisfactory yields (49-71%) with diversely substituted diazonium salts were achieved by using 1,3-dibutylimidazolium chloride in the presence of a bimetallic Zn/Cu catalyst.     

Ionic liquids based simultaneous ultrasonic and microwave assisted extraction of phenolic compounds from burdock leaves

The ionic liquids based simultaneous ultrasonic and microwave assisted extraction (IL-UMAE) technique was first proposed and applied to isolate compounds. The ionic liquids comprising a range of four anions, five 1-alkyl-3-methylimidazolium derivatives were designed and prepared. The results suggested that varying the anion and cation both had apparent effects on the extraction of phenolics. The results also showed that irradiation power, time and solid–liquid ratio significantly affected the yields. The yields of caffeic acid and quercetin obtained by IL-UMAE were higher than those by regular UMAE. Compared with conventional heat-reflux extraction (HRE), the proposed approach exhibited higher efficiency (8–17% enhanced) and shorter extraction time (from 5 h to 30 s). The results indicated ILUMAE to be a fast and efficient extraction technique. Moreover, the proposed method was validated by the reproducibility and recovery experiments. The ILUMAE method provided good recoveries (from 96.1% to 105.3%) with RSD lower than 5.2%, which indicated that the proposed method was credible. Based on the designable nature of ionic liquids, and the rapid and highly efficient performance of the proposed approach, ILUMAE provided a new alternative for preparation of various useful substances from solid samples.     

Improved solubilization of pyromellitic dianhydride and 4,4′-oxydianiline in ionic liquid by the addition of zwitterion and their polycondensation

Three different ionic liquids were prepared and examined as solvents for polyimide synthesis. The solubility of 4,4′-oxydianiline and pyromellitic dianhydride as starting materials in ionic liquids was first evaluated, and then their polycondensation was carried out. Although these starting materials were hardly soluble in 1-benzyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide (3), addition of imidazolium type zwitterion, 1-(1-butyl-3-imidazolio)butane-4-sulfonate (ZI), certainly improved their solubility. When 3 containing 40 mol % ZI was used, nothing was phase separated from this mixed solution containing both starting materials after cooling down to room temperature. After preparing prepolymer in 3 containing 40 mol % of ZI at room temperature, polycondensation was carried out in the same solution at 100, 200, and then 300 °C for every 1 h to obtain polyimide. An inherent viscosity of the obtained polyimide (0.05 g in 10 ml concentrated sulfuric acid) was 1.3 dL g⁻¹, higher than that prepared in only 3 (0.9 dL g⁻¹). The higher average molecular weight of the polyimide was attributed to the improved solubility of the starting materials by the addition of ZI that enabled the preparation of the prepolymer, poly(amide acid), without heating before imidation.     

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][PF₆] ionic liquid and 8-hydroxyquinoline (oxine), which forms a highly fluorescent complex with Al³⁺, were chosen as the extraction solvent and chelating agent, respectively. The hydrophobic Al-oxine complex was extracted into the [Hpy][PF₆] 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 (3 s) and enrichment factor were 0.05 μg L⁻¹ and 100, respectively. The relative standard deviation (RSD) for six replicate determinations of 6 μg L⁻¹ Al was 1.7%. The calibration graph using the pre-concentration system was linear in the range of 0.06-15 μg L⁻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.     

Development of microwave-assisted extraction followed by headspace solid-phase microextraction and gas chromatography-mass spectrometry for quantification of camphor and borneol in Flos Chrysanthemi Indici

In the work, microwave-assisted extraction (MAE) followed by headspace solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) was developed for quantitative analysis of the bioactive components of camphor and borneol in a traditional Chinese medicines (TCM) of Flos Chrysanthemi Indici. After systematical investigation, the optimal experimental parameters microwave power (400 W), irradiation time (4 min), fiber coating (PDMS/DVB fiber), extraction temperature (40 °C), extraction time (20 min), stirring rate (1100 rpm), and salt effect (no salt added) were investigated. The optimized method provided satisfactory precision (RSD values less than 12%), good recovery (from 86% to 94%), and good linearity (R² > 0.999). The proposed method was applied to quantitative analysis of camphor and borneol in Flos Chrysanthemi Indici samples from 11 different growing areas. To demonstrate the method feasibility, steam distillation was also used to analyze camphor and borneol in Flos Chrysanthemi Indici samples from these different growing areas. The very close results were obtained by the two methods. It has been shown that the proposed ME-HS-SPME-GC-MS is a simple, rapid, solvent-free and reliable method for quantitative analysis of camphor and borneol in TCM, and a potential tool for quality assessment of Flos Chrysanthemi Indici.     

Extraction and mechanism investigation of trace roxithromycin in real water samples by use of ionic liquid-salt aqueous two-phase system

The ionic liquid, as a green solvent, has several advantages over the organic solvents in traditional liquid-liquid extraction. Aqueous two-phase system (ATPS) consisting of a hydrophilic ionic liquid (1-butyl-3-methylimidazolium tetrafluoraborate, [Bmim]BF₄) and Na₂CO₃, which is a novel, simple, non-toxic and effective sample pretreatment technique coupled with molecular fluorescence spectrophotometry, was developed for the simultaneous separation, enrichment and rapid analysis of roxithromycin. The extraction yield of roxithromycin in [Bmim]BF₄-Na₂CO₃ aqueous two-phase system is influenced by the types of salts, concentrations of Na₂CO₃ and [Bmim]BF₄, as well as the extracting temperature. Under the optimum conditions, the average extraction efficiency is up to 90.7%. The mechanism of ionic liquid-salt ATPS formation was discussed by hydration theory, and the extraction mechanism of the [Bmim]BF₄-salt ATPS was investigated by FT-IR spectroscopy and UV-vis spectroscopy. The results demonstrate that no chemical (bonding) interactions are observed between ionic liquid and roxithromycin, while the nature properties of the roxithromycin are not altered. This method was practical when applied to the analysis of roxithromycin in real water samples with the detection limit of 0.03 μg mL⁻¹, relative standard deviation (RSD) of 1.9% (n = 13), and linear ranges of 1.00-20.00 μg mL⁻¹. The proposed extraction technique will be promising in the separation of other small biomolecules.