离子液体型表面活性剂研究

以1-甲基咪唑为原料, 制备了6个常规离子液体: 1-正丁基-3-甲基咪唑四氟硼酸盐及六氟磷酸盐(简称[bmim][BF₄]及[bmim][PF₆])、1-正己基-3-甲基咪唑四氟硼酸盐及六氟磷酸盐(简称[hmim][BF₄]及[hmim][PF₆])、1-正十六烷基-3-甲基咪唑四氟硼酸盐及六氟磷酸盐(简称[C₁₆mim][BF₄]及[C₁₆mim][PF₆])和4个功能化离子液体: 1-(2-羟乙基)-3-甲基咪唑四氟硼酸盐及六氟磷酸盐(简称[2-hemim][BF₄]及[2-hemim][PF₆])、1-乙氧羰基甲基-3-甲基咪唑四氟硼酸盐及六氟磷酸盐(简称[eocmmim][BF₄]及[eocmmim][PF₆]). 研究了这两类离子液体的一些物理性能, 旨在挖掘离子液体在香料香精化妆品工业中的应用价值. 分别检测了它们与一般溶剂的互溶性, 并测定了它们的表面张力和发泡性能, 实验结果表明, 仅[C₁₆mim][BF₄]和[C₁₆mim][PF₆]具有发泡性能, 发泡力分别为68和120 mm.     

Reverse ATRP Process of Methacrylonitrile in [C4mim][PF6]

In this original experiment, an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([C₄mim][PF₆]), was used as the reaction media for reverse atom transfer radical polymerization of methacrylonitrile (MAN) initiated by azobisisobutyronitrile (AIBN) with FeCl₃ and isophthalic acid (IA) as catalyst and ligand. The polymerization in [C₄mim][PF₆] proceeded in a well-controlled manner as evidenced by kinetic studies. Compared with the polymerization in N, N-dimethylformamide (DMF), the polymerization in [C₄mim][PF₆] not only showed better control of molecular weight and narrower molecular weight distribution but also provided more rapid reaction rate with the ratio of [MAN]:[AIBN]:[FeCl₃]:[IA] at 300:1:2:4. The block copolymer PMAN-b-PSt was obtained via a conventional ATRP process in [C₄mim][PF₆] by using the resulting PMAN as macroinitiator. [C₄mim][PF₆] and FeCl₃/IA could be easily recycled and reused and had no effect on the living nature of reverse atom transfer radical polymerization of MAN.     

Pd-catalyzed asymmetric alternating co-polymerization of propene with carbon monoxide using ionic liquids

A protocol for Pd-catalyzed stereoselective co-polymerization of propene and carbon monoxide using chiral ligands, such as (2S,3S)-DIOP and (R)-P-Phos in [C₄mim][PF₆]/[C₆mim][PF₆] as an ionic liquid medium was developed. With (2S,3S)-DIOP as chiral ligand and [C₄mim][PF₆] as medium, the Pd-catalyzed co-polymerization of propene and CO gave almost completely regioregular polyketones, and the product polymer showed moderate stereoregularity (61% of ℓ-diads). The highest molar optical rotation = +15.9 and polydispersity = 1.2 were attained when (R)-P-Phos was used as the ligand and [C₆mim]PF₆ as the solvent. The co-polymer exhibited regioregularity of H–H/H–T/T–T (%) = 17:66:17.     

Influence of ionic liquids on actinides extraction by diphenyl(dibutyl)carbamoylmethylphosphine oxide in different solvents from nitric acid solution

Influence of ionic liquids (ILs) addition (1?C50 wt%) on extraction efficiency of actinides by diphenyl(dibutyl)carbamoylmethylphosphine oxide (Ph₂Bu₂) from 3 M HNO₃ has been studied. Am(III) distribution ratios in two-phase systems 0.1 M Ph₂Bu₂ in either DCE or CHCl₃?C3 M HNO₃ depending on the nature of additional ionic liquids: imidazolium-based ILs: [C₄mim][PF₆], [C₄mim][BF₄] and phosphonium-based ILs: PPF₆, PBF₄ and PCl were determined. The highest value of Am(III) extraction ratio change (1040) was found on addition of PPF₆ to Ph₂Bu₂ in CHCl₃. Extraction of Pu(IV) and U(VI) by 0.001 M Ph₂Bu₂ in the presence of [C₄mim][PF₆] in DCE, CHCl₃ or meta-nitrobenzotrifluoride (NBTF) have been investigated. The greatest enhancement of extraction efficiency was observed using CHCl₃, the least polar studied solvent. Using a mixture of conventional solvent and ionic liquid as a solvent for extractant enables one to increase distribution ratios and reduce viscosity of organic phase as compared with ionic liquid viscosity. The marked increase of Am(III), Pu(IV) and U(VI) extraction extent by Ph₂Bu₂ on addition of ionic liquids to the extent of 10 wt% permit one essentially to diminish amounts considerably more expensive carbamoylmethylphosphine oxide(the general name is CMPO) used in TRUEX process.     

Extraction and high performance liquid chromatographic determination of 3-indole butyric acid in pea plants by using imidazolium-based ionic liquids as extractant

In this paper, imidazolium-based ionic liquids [C₄mim][PF₆], [C₆mim][PF₆], [C₈mim][PF₆], [C₆mim][BF₄] and [C₈mim][BF₄] were tested as extracting solvents for removal of 3-indole butyric acid (IBA) from aqueous media with subsequent determination using HPLC. Percent extraction of IBA was strongly affected by pH of aqueous phases and the chemical structures of ionic liquids (ILs). Extraction of IBA was quantitative in the pH values lower than pK_a of IBA. Considering both extraction and stripping efficiencies of IBA, [C₄mim][PF₆] was found to act more efficient than other studied ILs. Capacity of [C₄mim][PF₆] was 17.6 × 10⁻⁴ mmol IBA per 1.0 mL of IL. Ionic strength of aqueous phase and temperature had shown no serious effects on extraction efficiency of IBA. A preconcentration factor of 100 and a relative standard deviation of 1.16% were obtained. It was found that ionic liquid phase was reusable almost five times for extraction/stripping purposes. 3-Indole acetic acid showed interferential effect in the extraction step. In order to assess the applicability of the method, extraction and stripping of IBA from pea plants and some other samples were studied.     

Calorimetric Study on the Ion Pairing and Aggregation of 1-Ethyl-3-Methylimidazolium bis(trifluoromethylsulfonyl)amide ([C2mim][NTf2]) and Related Ionic Liquids in the Low-Dielectric Constant Solvent Chloroform

A calorimetric study of dissolution of the ionic liquids (ILs) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([C₂mim][NTf₂]), 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([C₆mim][NTf₂]), and 1-hexyl-3-methylimidazolium tris(trifluoromethylsulfonyl)methide ([C₆mim][CTf₃]) into chloroform (CHCl₃) is presented with particular focus on [C₂mim][NTf₂]. The interpretation of the calorimetric data for [C₂mim][NTf₂] was aided by additional NMR self-diffusion measurements and viscosity measurements that through the Stokes–Einstein equation provided information about the average size of the species present. It is evident that the main equilibrium species are ion pairs and aggregates. An estimate for the enthalpy contribution from aggregate formation for [C₂mim][NTf₂] was found to be ?2.09 kJ per mol of added IL at 288.2 K and slightly decreasing in magnitude to ?1.11 kJ·mol^?1 at 318.2 K. While all three ILs release heat upon dissolution into CHCl₃, different temperature trends are observed demonstrating the fine balance of competing contributions from breaking IL interactions, cavity formation for the solutes to reside in, and the establishment of new solute–solvent interactions.     

Rhodium(I) phosphine complexes containing bidentate unsaturated thio ligands: II. Reactions with O2 and H2

The rhodium(I) complexes (Ph₃P)₂Rh[Me₂NC(S)NC(S)NMe₂], (Ph₃P)₂Rh[SC(S)NMe₂] and (Ph₃P)₂Rh[PhNC(S)NMe₂] react with O₂ to give 1/1 dioxygen adducts. In solution, trans-(Ph₃P)₂Rh(O₂)[Me₂NC(S)NC(S)NMe₂], cis- and trans-(Ph₃P)₂Rh(O₂)[SC(S)NMe₂] and cis- and trans-(Ph₃P)₂Rh(O₂)[PhNC(S)NMe₂] are observed. For (Ph₃P)₂Rh(O₂)[PhNC(S)NMe₂], there is a solvent effect on the initial cis—trans ratio and the rate of O=PPh₃ formation. In C₆H₆, O=PPh₃ formation from (Ph₃P)₂Rh(O₂)[PhNC(S)NMe₂] is inhibited by additional PPh₃.The reaction of (Ph₃P)₂Rh[Ph₂PC(S)NPh] with O₂ in the presence of additional PPh₃ gives O=PPh₃ and cis-(Ph₃P)₂Rh(O₂)[Ph₂P(O)C(S)NPh] as the only products. The same complex also can be prepared from (Ph₃P)₂Rh[Ph₂P(O)C(S)NPh] and O₂.Only (Ph₃P)₂Rh[PhNC(S)NMe₂] reacts with H₂ at room temperature to give (Ph₃P)₂RhH₂[PhNC(S)NMe₂], which is a catalyst for cyclohexene hydrogenation.     

Effect of imidazolium-based ionic liquids on the aggregation behavior of twin-tailed cationic gemini surfactant in aqueous solution

Micellization behavior of the twin-tailed surfactants can be modulated by the addition of various modifiers. Ionic liquids (ILs) are one of them and are documented here. The beauty of these environmentally benign neoteric molecules lies in their structural versatility. Here, we have investigated the effect of three ILs: 1-butyl-3-methylimidazolium bromide ([C₄mim][Br]), 1-hexyl-3-methylimidazolium bromide ([C₆mim][Br]), and 1-octyl-3-methylimidazolium bromide ([C₈mim][Br]) on the aggregation and surface adsorption behavior of cationic gemini surfactant, bis(hexadecyldimethyl ammonium)propane dibromide (16-3-16) through experimentally measured electrical conductivities, surface tensions, and by spectral methods (UV-vis absorbance and fluorescence measurements). The main focus of the study is to observe the effect of added ILs on the critical micelle concentration (cmc), various surface parameters, aggregation number, and size of the aggregates of gemini surfactant. The results show that the more hydrophobic ILs, that is, [C₆mim][Br] and [C₈mim][Br] behave as electrolyte at lower concentration and cosurfactant at higher concentration, whereas moderately hydrophobic IL [C₄mim][Br] acts as an electrolyte at all concentration ranges studied. The modulating effects of ILs were also compared with conventional electrolyte (NaBr) at similar conditions.     

Special Mixing Behavior of Chelate-based Ionic Liquid with Methanol

Compared to the general ionic liquids (ILs), a significant deviation of the binary mixtures of 1-decyl-3-methylimidazolium tri(hexafluoroacetylaceto)-copper(II) ([C₁₀mim][Cu(hfacac)₃]) with methanol was found, indicating the way methanol interacts with ILs might be governed by the special structure of the chelating anion. IR results showed that the (C2-H) of 1-decyl-3-methylimidazolium hexafluoroacetylacetonate ([C₁₀mim][hfacac]) blue-shifted more significantly than that of [C₁₀mim][Cu(hfacac)₃], meanwhile the (C=O) red-shifted in [C₁₀mim][Cu(hfacac)₃], which is contrast with that in [C₁₀mim][hfacac]. Two-dimensional correlation analysis of the FTIR spectra indicated that the chelating cavity has little effect on the sequence of the ILs sites that interact with methanol. Combined with small angle X-ray scattering (SAXS) results, the picture of mixing processes in these two systems were proposed. Methanol interacts directly with the anion followed by the cation in [C₁₀mim][hfacac], while methanol preferentially enters the chelating cavity and enhances the packing effect in the [C₁₀mim][Cu(hfacac)₃] system.     

Room temperature ionic liquid as a novel medium for liquid/liquid extraction of metal ions

Room temperature ionic liquids (RTILs) have been used as novel solvents to replace traditional volatile organic solvents in organic synthesis, solvent extraction, and electrochemistry. The hydrophobic character and water immiscibility of certain ionic liquids allow their use in solvent extraction of hydrophobic compounds. In this work, a typical room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate [C₄mim][PF₆], was used as an alternative solvent to study liquid/liquid extraction of heavy metal ions. Dithizone was employed as a metal chelator to form neutral metal-dithizone complexes with heavy metal ions to extract metal ions from aqueous solution into [C₄mim][PF₆]. This extraction is possible due to the high distribution ratios of the metal complexes between [C₄mim][PF₆] and aqueous phase. Since the distribution ratios of metal dithiozonates between [C₄mim][PF₆] and aqueous phase are strongly pH dependent, the extraction efficiencies of metal complexes can be manipulated by tailoring the pH value of the extraction system. Hence, the extraction, separation, and preconcentraction of heavy metal ions with the biphasic system of [C₄mim][PF₆] and aqueous phase can be achieved by controlling the pH value of the extraction system. Preliminary results indicate that the use of [C₄mim][PF₆] as an alternate solvent to replace traditional organic solvents in liquid/liquid extraction of heavy metal ions is very promising.     

Chemie polyfunktioneller Moleküle. 82. Neue Rhodium(I)-Chelatkomplexe mit N,N-Bis(diphenylphosphino)alkyl- und -arylaminen

Chemistry of Polyfunctional Molecules. 82. New Rhodium(1) Chelate Complexes with N,N-Bis(diphenylphosphino) alkyl- and -arylamines . [Rh(μ-Cl)(CO)₂]₂ ( 1 ) reacts with (Ph₂P)₂NR (2, a: R = C₆H₅, b: R = p-C₆H₄CH₃) in a molar ratio of 1:2 to give the square plane, ionic complexes [Rh{(PH₂P)₂NR}₂] [cis-Rh(CO)₂Cl₂] ( 3a, b ). By the reactions of [Rh(μ-Cl)(C₈H₁₂)]₂(C₈H₁₂ = 1.5-Cyclooctadiene) (4) with (Ph₂P)₂NR ( 2a–d ) (c: R = CH₃, d: R = C₂H₅) in the molar ratios of 1:4 the square plane 1:1 electrolytes [Rh{(Ph₂P)₂NR}₂]Cl ( 5a–d ) are obtained. Upon treatment of 5a–d in dichloromethane with CO the complexes [Rh(CO){(Ph₂P)₂NR}₂]Cl ( 6a–d ) are formed. They are only stable in solution and in CO atmosphere and were identified by infrared spectroscopy. The new complexes have been characterized, as far as possible, by conductometry, IR; FIR, Raman, ³¹P-NMR, and ¹H-NMR spectra.     

Selective extraction of Cs(I) using 1,3-[(2,4-diethylheptylethoxy)oxy]-2,4-crown-6-calix[4]arene in ionic liquid solvents and its application to the treatment of high-level liquid waste

To separate heat-generating Cs from high-level liquid waste (HLLW), the extraction of Cs(I) using 1,3-[(2,4-diethylheptylethoxy)oxy]-2,4-crown-6-calix[4]arene (calix[4]arene-R14) in combination with 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) ionic liquids ([C _n mim][NTf₂], where n?=?2, 4, and 6) was investigated. Under moderately acidic conditions, the calix[4]arene-R14/[C _n mim][NTf₂] system showed a higher extraction efficiency (E_Cs) than that exhibited by the conventional calix[4]arene-R14/dichloromethane system. All extraction processes reached equilibrium within 5 min. Slope analysis revealed that the Cs:calix[4]arene-R14 inclusion complex has a 1:1 stoichiometry. The extraction was found to be exothermic and influenced by the presence of Na(I). These extraction systems exhibited high efficiency and selectivity for Cs(I) in simulated HLLW.     

Thermodynamic properties and polymorphism of 1-alkyl-3-methylimidazolium bis(triflamides)

Heat capacities in a range of temperatures of (5 to 370) K, enthalpies and temperatures of phase transitions for 1-ethyl-3-methylimidazolium bis(triflamide) ([C₂mim][NTf₂]) and 1-octyl-3-methylimidazolium bis(triflamide) ([C₈mim][NTf₂]) have been determined by adiabatic calorimetry. [C₂mim][NTf₂] has been found to form four crystalline phases with different fusion temperatures. Formation of the phases can be controlled by the temperature of annealing during crystallization. [C₈mim][NTf₂] forms three sequences of crystalline modifications, each including two polymorphs. Based on results of the measurements, thermodynamic functions for the compounds under study have been calculated.A heat-capacity anomaly near T = 230 K reported earlier for [C₄mim][NTf₂] and [C₆mim][NTf₂] have been found in some crystalline modifications of both the studied compounds. The position of the anomaly depends on the temperature of annealing of the crystals.     

Ionic liquids as porogens in the microwave-assisted synthesis of methacrylate monoliths for chromatographic application

Several imidazolium-based ionic liquids (ILs) with varying cation alkyl chain length (C₄–C₁₀) and anion type (tetrafluoroborate ([BF₄]⁻), hexafluorophosphate ([PF₆]⁻) and bis(trifluoromethylsulfonyl)imide ([Tf₂N]⁻)) were used as reaction media in the microwave polymerization of methacrylate-based stationary phases. Scanning electron micrographs and backpressures of poly(butyl methacrylate-ethylene dimethacrylate) (poly(BMA-EDMA)) monoliths synthesized in the presence of these ionic liquids demonstrated that porosity and permeability decreased when cation alkyl chain length and anion hydrophobicity were increased. Performance of these monoliths was assessed for their ability to separate parabens by capillary electrochromatography (CEC). Intra-batch precision (n = 3 columns) for retention time and peak area ranged was 0.80–1.13% and 3.71–4.58%, respectively. In addition, a good repeatability of RSD_{Retention time} = <0.30% and ∼1.0%, RSD_{Peak area} = <1.30% and <4.3%, and RSD_Efficiency = <0.6% and <11.5% for intra-day and inter-day, respectively exemplify monolith performance reliability for poly(BMA-EDMA) fabricated using 1-hexyl-3-methylimidazolium tetrafluoroborate ([C₆mim][BF₄]) porogen. This monolith was also tested for its potential in nanoLC to separate protein digests in gradient mode. ILs as porogens also fabricated different alkyl methacrylate (AMA) (C4–C18) monoliths. Furthermore, employing binary IL porogen mixture such as 1-butyl-3-methylimidazolium tetrafluoroborate ([C₄mim][BF₄]) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C₄mim][Tf₂N]) successfully decreased the denseness of the monolith, than when using [C₄mim][Tf₂N] IL alone, enabling a chromatographic run to be performed with 1:1 ratio produced baseline separation for the analytes. The combination of ILs and microwave irradiation made polymer synthesis very fast (∼10 min), entirely green (organic solvent-free) and energy saving process.     

Reactions of Thiocarbamoyl compounds with vaska complexes: mechanism and stereochemistry

Bis(dimethylthiocarbamoyl)sulfide, (Me₂NCS)₂S, reacts with (PH₃P)₂MCOCl complexes giving ionic species [Ph₃PM(η²-CSNMe₂)(S₂CNMe₂)CO]X (M = Rh, Ir; X = Cl, PF₆) as kinetic products. On standing solution, [Ph₃PRh(η²-CSNMe₂)(S₂CNMe₂)CO]Cl is slowly transformed into the thermodynamic product Ph₃PRh(η²-CSNMe₂)S₂CNMe₂)Cl. The known reactions of Vaska-type complexes with Me₂NCSCl to give [trans-(Ph₃P)₂Ir(η²-CSNMe₂)COCl]Cl and trans-(Ph₃P)₂Rh(η²-CSNMe₂)Cl₂ probably follow a similar course. (PH₃P)RuNOCl reacts with (Me₂NCS)₂S and Me₂NCSCl in the same way as (Ph₃P)₂IrCOCl, but reacts with (Me₂NCS)₂NPh to give [trans-(Ph₃P)₂Ru(η²-CSNMe₂)NOCl]PF₆. The mechanism and stereochemistry of these reactions are discussed. Reactions were monitored by NMR spectroscopy in an attempt to identify intermediate η¹-thiocarboxamido complexes, but no such species could be detected.     

Selective adsorption of luteolin and aloe-emodin on ionic liquids-bonded silica

Ionic liquids (ILs)-bonded silica adsorbents were prepared by chemical modification of the silica surface using N-alkylimidazolium-based ILs with Cl^?, BF₄ ^?, PF₆ ^? or NO₃ ^? anion, and applied to selective separation of the model mixture of luteolin and aloe-emodin. Among the investigated ILs-bonded silica materials, the silica grafted with N-octyllimidazolium hexafluorophosphate ([C₈mim]PF₆@SiO₂) exhibited higher adsorption capacity and selectivity of luteolin from the model mixed solution of luteolin and aloe-emodin. The isotherm data of luteolin on [C₈mim]PF₆@SiO₂ correlated better to the Freundlich model than the Langmuir model, and the calculated thermodynamic parameters indicated that the adsorption of luteolin was spontaneous and exothermic. The dynamic adsorption and elution experiments demonstrated that the high adsorption capacity and good desorption efficiency of luteolin on fixed bed packed with the [C₈mim]PF₆@SiO₂. Moreover, the results from batch adsorption and dynamic adsorption showed well selective separation towards the model mixture of luteolin and aloe-emodin.     

Ionic liquids enhanced oil recovery from oily sludge-experiment and mechanism

The oily sludge would cause environment pollution, and would cause the heavy oil waste. Therefore, it was vital for us to find novel methods to obtain heavy oil from the oily sludges. In this study, the [C₁₂mim][PF₆] and [C₁₂mim][Br] ionic liquids(ILs) were used to enhance the oil recovery. The toluene could obtain the highest oil recovery, and both the two ILs could increase the oil recovery. Toluene could obtain the highest oil recovery (89.4 wt%), and n-octane could obtain the lowest oil recovery (76.8 wt%). [C₁₂mim] [PF₆] could efficiently increase the heavy oil recovery to 91.2 wt%(by toluene). The [C₁₂mim][Br] could increase the heavy oil recovery further. Both the [C₁₂mim] [PF₆] and the [C₁₂mim][Br] ionic liquids could increase the heavy ois C/H ratio, decrease heavy oil viscosity and increase the sands hydrophilicity. The [C₁₂mim][Br] ionic liquids showed better effect. In addition, the ionic liquids could increase the solvents recovery, and the ionic liquids recovery were high. Therefore, the ionic liquids enhanced oil recovery could be recycled to ten times. The two ionic liquids could effectively decrease the heavy oil interaction force, and when the ionic liquids increased to 200 ppm, the force remained stable. In the end, the ionic liquids enhancing solvent extraction mechanism was put forward.     

An unusual oxidative addition-ligand elimination reaction. Preparation and structure of RhCl2(PMe2Ph)2(C3Ph3)

The sym-triphenylcyclopropenium cation (C₃Ph₃⁺) stabilized as the Cl^? or PF₆^? salt, undergoes facile reactions at room temperature with trans-Rh(CO)Cl(PMe₂Ph)₂ to produce complexes which result from the oxidative cleavage of the ring and decarbonylation of the organometallic reactant. The product of the C₃Ph₃⁺Cl^? reaction has been fully characterized by X-ray analysis and is shown to be RhCl₂(PMe₂Ph)₂(C₃Ph₃).     

Separation of no-carrier-added 109Cd from natural silver target using RTIL 1-butyl-3-methylimidazolium hexafluorophosphate

The room temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium hexafluorophosphate [C₄mim][PF₆] has various applications in the separation of a range of metal ions replacing volatile and toxic traditional organic solvents in liquid–liquid extraction systems. In this study, the RTIL [C₄mim][PF₆] was used to separate no-carrier-added (NCA) ¹⁰⁹Cd from α-particle irradiated Ag target. A natural Ag foil was bombarded by 30 MeV α-particles to produce ¹⁰⁹Cd. After the decay of all co-produced short-lived products, NCA ¹⁰⁹Cd was separated from the bulk Ag using [C₄mim][PF₆] as extractant from HNO₃ medium. Ammoniumpyrrolidine dithiocarbamate (APDC) was used as a complexing agent. At the optimum condition, 3 M HNO₃, 0.01 M APDC in presence of [C₄mim][PF₆], ~99 % bulk Ag was extracted to the IL phase, leaving NCA ¹⁰⁹Cd in the aqueous phase. The amount of Ag became negligibly small after re-extraction in the same condition. The ionic liquid was recovered by washing it with 1 M HCl.     

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.