Orthogonal array optimization of ionic liquid based dispersive liquid-liquid microextraction for toxic anilines in foods

A simple and rapid method of ionic liquid based dispersive liquid-liquid microextraction(DLLME) combining with high performance liquid chromatography(HPLC) was developed for the analysis of four toxic anilines in flour steamed bread and maize steamed bread.Several possible influential factors such as the type of ionic liquid and disperser solvent,extraction time,sample pH,ionic strength and the volume of ionic liquid and disperser solvent were optimized using single factor experiments and orthogonal array design(OAD) with OA 25(5 4) matrix.Analysis of variance(ANOVA) and percent contribution(PC) were used to investigate the significance of the factors of OAD.Sample pH and ionic strength are statistically demonstrated two chief factors.Under the optimum condition,the method exhibits a good linearity(r 2 > 0.99) over the studied range(50-1000 ng g 1) for anilines.The extraction factors and recoveries for the anilines in two kinds of steamed breads ranged between 34.1%-73.3% and 44.3%-95.3%,respectively.The limit of detections(LODs) and limit of quantitations(LOQs) ranged between 10-15 ng g 1 and 30-45 ng g-1.     

Dispersive liquid–liquid microextraction and spectrophotometric determination of cobalt in water samples

A new simple and rapid dispersive liquid–liquid microextraction has been applied to preconcentrate trace levels of cobalt as a prior step to its determination by spectrophotometric detection. In this method a small amount of chloroform as the extraction solvent was dissolved in pure ethanol as the disperser solvent, then the binary solution was rapidly injected by a syringe into the water sample containing cobalt ions complexed by 1-(2-pyridylazo)-2-naphthol (PAN). This forms a cloudy solution. The cloudy state was the result of chloroform fine droplets formation, which has been dispersed in bulk aqueous sample. Therefore, Co-PAN complex was extracted into the fine chloroform droplets. After centrifugation (2 min at 5000 rpm) these droplets were sedimented at the bottom of conical test tube (about 100 µL) and then the whole of complex enriched extracted phase was determined by a spectrophotometer at 577 nm. Complex formation and extraction are usually affected by some parameters, such as the types and volumes of extraction solvent and disperser solvent, salt effect, pH and the concentration of chelating agent, which have been optimised for the presented method. Under optimum conditions, the enhancement factor (as the ratio of slope of preconcentrated sample to that obtained without preconcentration) of 125 was obtained from 50 mL of water sample, and the limit of detection (LOD) of the method was 0.5 µg L^?1and the relative standard deviation (RSD, n = 5) for 50 µg L^?1 of cobalt was 2.5%. The method was applied to the determination of cobalt in tap and river water samples.     

Cold-induced aggregation microextraction: a novel sample preparation technique based on ionic liquids

In this research, a novel microextraction technique based on ionic liquids (ILs) termed cold-induced aggregation microextraction (CIAME) is developed. In this method, very small amounts of 1-hexyl-3-methylimidazolium hexafluorophosphate [Hmim][PF₆] and 1-hexyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide [Hmim][Tf₂N] (as extractant solvents) were dissolved in a sample solution containing Triton X-114 (as an anti-sticking agent). Afterwards, the solution was cooled in the ice bath and a cloudy solution was formed. After centrifuging, the fine droplets of extractant phase were settled to the bottom of the conical-bottom glass centrifuge tube.CIAME is a simple and rapid method for extraction and preconcentration of metal ions from water samples and can be applied for the sample solutions containing high concentration of salt and water miscible organic solvents. Furthermore, this technique is much safer in comparison with the organic solvent extraction.Performance of the technique was evaluated by determination of the trace amounts of mercury as a test analyte in several real water samples. Michler thioketone (TMK) was chosen as a complexing agent. Analysis was carried out using spectrophotometric detection method. Type and amount of IL and the surfactant, temperature and the other parameters were optimized. Under the optimum conditions, the limit of detection (LOD) of the method was 0.3 ng mL⁻¹ and the relative standard deviation (R.S.D.) was 1.32% for 30 ng mL⁻¹ mercury.     

Extraction and determination of hormones in cosmetics by homogeneous ionic liquid microextraction high-performance liquid chromatography

The homogeneous ionic liquid microextraction was applied to the extraction of hormones from cosmetics and the hormones were determined by high-performance liquid chromatography. 1-Hexyl-3-methylimidazolium tetrafluoroborate was used as extraction solvent. Ammonium hexafluorophosphate as used as ion-pairing agent. Several experimental parameters, including the volume of 1-hexyl-3-methylimidazolium tetrafluoroborate, amount of ammonium hexafluorophosphate and sodium chloride, extraction and centrifuge time, and the pH value, were optimized. The limits of detection and quantification for the analytes ranged from 0.03 to 0.24 ng/mL and from 0.10 to 0.79 ng/mL, respectively. The precision for determining the hormones was lower than 5.2%. The proposed method was successfully developed for the determination of hormones in real cosmetic samples.     

A spectrophotometric method for manganese determination in water samples based on ion pair formation and dispersive liquid–liquid microextraction

In this work, a simple, inexpensive, and environmentally friendly extractive spectrophotometric method for the determination of manganese is suggested. The method is based on the formation and dispersive liquid–liquid microextraction (DLLME) of a violet-coloured ion pair of Mn(II) with 1,3,3-trimethyl-2-[3-(3-methyl-3H-benzothiazol-2-ylidene)-propenyl]-3H-indolium (BTIC) in the presence of 1-nitroso-2-naphthol (HL) as ligand, and subsequent UV-VIS spectrophotometric detection at 560?nm of the ion pair formed. The appropriate experimental conditions for the DLLME procedure were found to be: a pH of 9.5; 0.12?mmol?L^?1 of BTIC; extraction solvent – toluene containing 1.75?mmol?L^?1 of HL; disperser solvent – methanol; auxiliary solvent – tetrachloromethane. Beer's law is obeyed in the range 0.055–0.88 µg?mL^?1 of Mn(II). The limit of detection (LOD), calculated based on three times of the standard deviation of the blank test (n?=?10), was found to be 0.004?µg?mL^?1 of Mn(II). The precision (as relative standard deviation, RSD%) and accuracy (as recovery percentage, R%) of the method were examined by performing five replicate determinations at four concentration levels over two days and varied between 1.2 and 3.8, and 97.7 and 104.5, respectively. The suggested method was successfully applied to the analysis of various water samples (mineral water, spring water and drinking water).     

In situ solvent formation microextraction based on ionic liquids: A novel sample preparation technique for determination of inorganic species in saline solutions

In this research, a novel microextraction technique based on ionic liquids (ILs) termed in situ solvent formation microextraction (ISFME) is developed. In this method, small amount of sodium hexafluorophosphate (NaPF₆, as an ion-pairing agent) was added to the sample solution containing very small amount of 1-hexyl-3-methylimidazolium tetrafluoroborate ([Hmim][BF₄], as hydrophilic IL). A cloudy solution was formed as a result of formation of fine droplets of 1-hexyl-3-methylimidazolium hexafluorophosphate [Hmim][PF₆]. After centrifuging, the fine droplets of the extractant phase settled to the bottom of the conical-bottom glass centrifuge tube.ISFME is a simple and rapid method for extraction and preconcentration of metal ions from water samples and can be applied for the sample solutions containing very high concentrations of salt. Furthermore, this technique is much safer in comparison with the organic solvent extraction.Reliability of the introduced methodology was evaluated by analyzing water reference material. ISFME was successfully applied to determining mercury (II) in several real water samples. Michler thioketone (TMK) was chosen as a complexing agent. Analysis was carried out using spectrophotometric detection method. Type and amount of IL, temperature and the other parameters were optimized. Under the optimum conditions, the limit of detection (LOD) was 0.7 ng mL⁻¹ and the relative standard deviation (R.S.D.) was 1.94% for 40 ng mL⁻¹ mercury.     

基于离子液体的分散液液微萃取-柱前荧光衍生高效液相色谱法测定水样中8种磺胺类药物

建立了一种基于离子液体的分散液液微萃取技术结合柱前荧光衍生高效液相色谱(IL-DLLME-HPLC-FL)对8种磺胺类药物进行检测的方法,并成功应用于实际环境水样的分析。实验考察了萃取参数对磺胺萃取效率的影响及衍生产物的稳定性。最佳实验条件:以40 μL [C₆MIM]PF₆]为萃取剂,0.1 mL丙酮为分散剂,对pH=4且不含NaCl的水溶液进行不超声的分散液液微萃取,并衍生化反应6 h。结果表明:在最佳实验条件下,该法在0.2~10 μg/L和10~500 μg/L两个浓度范围内线性良好,线性相关系数r ≥0.9989;检出限为0.08~0.5 μg/L (S/N=3)。对实验室自来水、湖水、珠江水、池塘水分别加标5、50、200 μg/L的回收率为87.2%~101.4%,相对标准偏差为3.7%~6.2%。该法环保、简便,可用于测定实际水样中磺胺类药物。     

Combination of ionic liquid dispersive liquid-phase microextraction and high performance liquid chromatography for the determination of triazine herbicides in water samples

A temperature-controlled ionic liquid dispersive liquid-phase microextraction in combination with high performance liquid chromatography was developed for the enrichment and determination of triazine herbicides such as cyanazine,simazine,and atrazine in water samples.1-Octyl-3-methylimidazolium hexafluorophosphate([C8MIM][PF6]) was selected as the extraction solvent.Several experimental parameters were optimized.Under the optimal conditions,the linear range for cyanazine was in the concentration range of 0.5–80 mg/L and the linear range for simazine and atrazine was in the range of1.0–100 mg/L.The limit of detection(LOD,S/N = 3) was in the ranges of 0.05–0.06 mg/L,and the intra day and inter day precision(RSDs,n = 6) was in the ranges of 3.2%–6.6% and 4.8%–8.9%,respectively.Four real water samples were analyzed with the developed method,and the experimental results showed that the spiked recoveries were satisfactory.All these exhibited that the developed method was a valuable tool for monitoring such pollutants.     

Trace determination of hexabromocyclododecane diastereomers in water samples with temperature controlled ionic liquid dispersive liquid phase microextraction

A novel temperature controlled ionic liquid dispersive liquid phase microextraction(TCIL-DLPME) coupled with rapid resolution liquid chromatography-electrospray tandem mass spectrometry(RRLC-ESI-MS-MS) has been developed for the enrichment and determination of three hexabromocyclododecane diastereomers(HBCDs) in water samples.Green solvent ionic liquid(IL) was used as extraction solvent instead of toxic organic solvents.This technique also avoided the usage of dispersive solvent.Some important parameters that might affect the extraction efficiency were optimized.Under the optimum conditions,good linear relationship,sensitivity and reproducibility were obtained.All the limits of detection for the three diastereomers were 0.1 ng/ mL.The linear range was obtained in the range of 1-100 ng/mL for the total amount of three HBCD diastereomers.It was satisfactory to analyze real environmental water samples with the recoveries ranging from 77.2%to 99.3%.The main advantage of the method is toxic organic solvent-free.     

Dispersive liquid–liquid microextraction combined with high performance liquid chromatography-DAD detection for the determination of sulfonylurea herbicides in water samples

A new method for the determination of four sulfonylurea herbicides (metsulfuron-methyl, chlorsulfuron, bensulfuron-methyl and chlorimuron-ethyl) in water samples was developed by dispersive liquid–liquid microextraction coupled with high performance liquid chromatography-diode array detector. Parameters that affect the extraction efficiency, such as the kind and volume of the extraction and disperser solvent, extraction time and salt addition, were investigated and optimised. Under the optimum conditions, the enrichment factors were in the range between 102 and 216. The linearity of the method was obtained in the range of 1.0–100 ng mL^?1 with the correlation coefficients (r) ranging from 0.9982 to 0.9995. The method detection limits were 0.2–0.3 ng mL^?1. The proposed method has been successfully applied to the analysis of target sulfonylurea herbicides in river, stream and well water samples with satisfactory results.     

Gas chromatography with mass spectrometry for the determination of phthalates preconcentrated by microextraction based on an ionic liquid

A new procedure is proposed for the analysis of migration test solutions obtained from plastic bottles used in the packaging of edible oils. Ultrasound‐assisted emulsification microextraction with ionic liquids was applied for the preconcentration of six phthalate esters: dimethylphthalate, diethylphthalate, di‐n‐butylphthalate, n‐butylbenzylphthalate, di‐2‐ethylhexylphthalate, and di‐n‐octylphthalate. The enriched ionic liquid was directly analyzed by gas chromatography and mass spectrometry using direct insert microvial thermal desorption. The different factors affecting the microextraction efficiency, such as volume of the extracting phase (30 μL of the ionic liquid) and ultrasound application time (25 s), and the thermal desorption step, such as desorption temperature and time, and gas flow rate, were studied. Under the selected conditions, detection limits for the analytes were in the 0.012–0.18 μg/L range, while recovery assays provided values ranging from 80 to 112%. The use of butyl benzoate as internal standard increased the reproducibility of the analytical procedure. When the release of the six phthalate esters from the tested plastic bottles to liquid simulants was monitored using the optimized procedure, analyte concentrations of between 1.0 and 273 μg/L were detected.     

Comparison of three different dispersive liquid–liquid microextraction modes performed on their most usual configurations for the extraction of phenolic,neutral aromatic,and amino compounds from waters

In this work we seek clues to select the appropriate dispersive liquid–liquid microextraction mode for extracting three categories of compounds. For this purpose, three common dispersive liquid–liquid microextraction modes were compared under optimized conditions. Traditional dispersive liquid–liquid microextraction, in situ ionic liquid dispersive liquid–liquid microextraction, and conventional ionic liquid dispersive liquid–liquid microextraction using chloroform, 1‐butyl‐3‐methylimidazolium tetrafluoroborate, and 1‐hexyl‐3‐methylimidazolium hexafluorophosphate as the extraction solvent, respectively, were considered in this work. Phenolic, neutral aromatic, and amino compounds (each category included six members) were studied as analytes. The analytes in the extracts were determined by high‐performance liquid chromatography with UV detection. For the analytes with polar functionalities, the in situ ionic liquid dispersive liquid–liquid microextraction mode mostly led to better results. In contrast, for neutral hydrocarbons without polar functionalities, traditional dispersive liquid–liquid microextraction using chloroform produced better results. In this case, where dispersion forces were the dominant interactions in the extraction, the refractive index of solvent and analyte predicted the extraction performance better than the octanol/water partition coefficient. It was also revealed that none of the methods were successful in extracting hydrophilic analytes (compounds with the log octanol/water partition coefficient <2). The results of this study could be helpful in selecting a dispersive liquid–liquid microextraction mode for the extraction of various groups of compounds.     

Sorbent coatings for solid-phase microextraction based on mixtures of polymeric ionic liquids

Four polymeric ionic liquids based on two different cations, poly(1‐vinyl‐3‐hexylimidazolium) and poly(1‐vinyl‐3‐hexadecylimidazolium), combined with two different anions, bis[(trifluoromethyl)sulfonyl]imide (NTf) and chloride (Cl^?), were combined in various weight percentages and used as sorbent coatings for solid‐phase microextraction gas chromatography (SPME‐GC). The selectivity of the fiber coatings for 12 test analytes was examined. The extraction efficiency of n‐alcohols increased with an increase in the weight percentage of chloride ion in the sorbent coating. The ability to tune the interactions between the coating material and the analytes was exploited and resulted in distinct changes in the limits of detection for hydrogen‐bonding analytes with varying chloride ion content in the sorbent coating.     

Quantitation of antioxidants in water samples using ionic liquid dispersive liquid-liquid microextraction followed by high-performance liquid chromatography-ultraviolet detection

A simple and efficient method, ionic liquid-based dispersive liquid-liquid microextraction combined with high-performance liquid chromatography-ultraviolet detection (HPLC-UV), has been applied for the extraction and determination of some antioxidants (Irganox 1010, Irganox 1076 and Irgafos 168) in water samples. The microextraction efficiency factors were investigated and optimized: 1-hexyl-3-methylimidazolium hexafluorophosphate [C(6)MIM][PF(6)] (0.06 g) as extracting solvent, methanol (0.5 mL) as disperser solvent without salt addition. Under the selected conditions, enrichment factors up to 48-fold, limits of detection (LODs) of 5.0-10.0 ng/mL and dynamic linear ranges of 25-1500 ng/mL were obtained. A reasonable repeatability (RSD≤11.8%, n=5) with satisfactory linearity (r(2)≥0.9954) of the results illustrated a good performance of the presented method. The accuracy of the method was tested by the relative recovery experiments on spiked samples, with results ranging from 85 to 118%. Finally, the method was successfully applied for determination of the analytes in several real water samples.     

Determination of polycyclic aromatic hydrocarbons in food samples by automated on-line in-tube solid-phase microextraction coupled with high-performance liquid chromatography-fluorescence detection

A simple and sensitive automated method, consisting of in-tube solid-phase microextraction (SPME) coupled with high-performance liquid chromatography-fluorescence detection (HPLC-FLD), was developed for the determination of 15 polycyclic aromatic hydrocarbons (PAHs) in food samples. PAHs were separated within 15 min by HPLC using a Zorbax Eclipse PAH column with a water/acetonitrile gradient elution program as the mobile phase. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 μL of sample using a CP-Sil 19CB capillary column as an extraction device. Low- and high-molecular weight PAHs were extracted effectively onto the capillary coating from 5% and 30% methanol solutions, respectively. The extracted PAHs were readily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. Using the in-tube SPME HPLC-FLD method, good linearity of the calibration curve (r > 0.9972) was obtained in the concentration range of 0.05–2.0 ng/mL, and the detection limits (S/N = 3) of PAHs were 0.32–4.63 pg/mL. The in-tube SPME method showed 18–47 fold higher sensitivity than the direct injection method. The intra-day and inter-day precision (relative standard deviations) for a 1 ng/mL PAH mixture were below 5.1% and 7.6% (n = 5), respectively. This method was applied successfully to the analysis of tea products and dried food samples without interference peaks, and the recoveries of PAHs spiked into the tea samples were >70%. Low-molecular weight PAHs such as naphthalene and pyrene were detected in many foods, and carcinogenic benzo[a]pyrene, at relatively high concentrations, was also detected in some black tea samples. This method was also utilized to assess the release of PAHs from tea leaves into the liquor.     

Ionic liquid foam floatation coupled with ionic liquid dispersive liquid–liquid microextraction for the separation and determination of estrogens in water samples by high‐performance liquid chromatography with fluorescence detection

An ionic liquid foam floatation coupled with ionic liquid dispersive liquid–liquid microextraction method was proposed for the extraction and concentration of 17‐α‐estradiol, 17‐β‐estradiol‐benzoate, and quinestrol in environmental water samples by high‐performance liquid chromatography with fluorescence detection. 1‐Hexyl‐3‐methylimidazolium tetrafluoroborate was applied as foaming agent in the foam flotation process and dispersive solvent in microextraction. The introduction of the ion‐pairing and salting‐out agent NH₄PF₆ was beneficial to the improvement of recoveries for the hydrophobic ionic liquid phase and analytes. Parameters of the proposed method including concentration of 1‐hexyl‐3‐methylimidazolium tetrafluoroborate, flow rate of carrier gas, floatation time, types and concentration of ionic liquids, salt concentration in samples, extraction time, and centrifugation time were evaluated. The recoveries were between 98 and 105% with relative standard deviations lower than 7% for lake water and well water samples. The isolation of the target compounds from the water was found to be efficient, and the enrichment factors ranged from 4445 to 4632. This developing method is free of volatile organic solvents compared with regular extraction. Based on the unique properties of ionic liquids, the application of foam floatation, and dispersive liquid–liquid microextraction was widened.     

离子液体作为新型光度法增敏剂测定铝的研究

离子液体是一类典型的低熔点的有机熔融盐[1].十几年来,由于离子液体本身特殊的性质,人们对其应用进行了许多研究,内容涉及到了有机合成[2]、多相催化[3]和传感器[4]等众多领域.离子液体在分析化学中的应用也有报道[5].     

Solid-phase extraction combined with headspace single-drop microextraction of chlorophenols as their methyl ethers and analysis by high-performance liquid chromatography-diode array detection

Solid-phase extraction (SPE) of phenol and chlorophenols, their derivatization to methyl ethers, headspace single-drop microextraction (HS-SDME) of methyl ethers using 1-butanol as extraction solvent, and direct transfer of the drop into the injector for high performance liquid chromatography with diode array detection (HPLC-DAD) have been reported. A flanged-end polytetrafluoroethylene sleeve, 3 mm × 0.5 mm, placed at the tip of the syringe needle, allowed the use of 10 μL solvent drop for extraction. The procedure has been optimized for variables involved in SPE and HS-SDME. A rectilinear relationship was obtained between the amount of chlorophenols and peak area ratio of their methyl ethers/internal standard (4-methoxyacetophenone) in the range 0.01-10 mg L⁻¹, correlation coefficient in the range 0.9956-0.9996, and limit of detection in the range 1.5-3.9 μg L⁻¹ when HS-SDME alone was used for sample preparation. When using coupled SPE and HS-SDME, the linear range obtained was 0.1-500 μg L⁻¹, correlation coefficient in the range 0.9974-0.9998, and the limit of detection in the range 0.04-0.08 μg L⁻¹. Spiked real samples have been analyzed with adequate accuracy, and application of the method has been demonstrated for the analysis of chlorophenols formed upon bamboo pulp bleaching.     

Preparation of ionic liquid based solid-phase microextraction fiber and its application to forensic determination of methamphetamine and amphetamine in human urine

A new solid-phase microextraction (SPME) procedure using an ionic liquid (IL) has been developed. Reusable IL-based SPME fiber was prepared for the first time by fixing IL through cross-linkage of IL impregnated silicone elastomer on the surface of a fused silica fiber. 1-Ethoxyethyl-3-methylimidazloium bis(trifluoromethane) sulfonylimide ([EeMim][NTf₂]) ionic liquid was employed as a demonstration and the prepared fiber was applied to the forensic headspace determination of methamphetamine (MAP) and amphetamine (AP) in human urine samples. Important extraction parameters including the concentration of salt and base in sample matrix, extraction temperature and extraction time were investigated and optimized. Combined with gas chromatography/mass spectrometry (GC/MS) working in selected ion monitoring (SIM) mode, the new method showed good linearity in the range of 20–1500 μg L⁻¹, good repeatability (RSD < 7.5% for MAP, and <11.5% for AP, n = 6), and low detection limits (0.1 μg L⁻¹ for MAP and 0.5 μg L⁻¹ for AP). Feasibility of the method was evaluated by analyzing human urine samples. Although IL-based SPME is still at the beginning of its development stage, the results obtained by this work showed that it is a promising simple, fast and sensitive sample preparation method.     

Temperature-assisted ionic liquid dispersive liquid-liquid microextraction combined with high performance liquid chromatography for the determination of anthraquinones in Radix et Rhizoma Rhei samples

In this article, a novel method termed as temperature-assisted ionic liquid dispersive liquid-liquid microextraction (TA IL-DLLME) combining high performance liquid chromatography with diode array detection (HPLC-DAD) was developed for the determination of anthraquinones in Radix et Rhizoma Rhei samples. The ionic liquid (1-hexyl-3-methylimidazolium hexafluorophosphate) was used to replace volatile organic solvent as an extraction solvent for the extraction of anthraquinones (aloe-emodin, rhein, emodin, chrysophanol and physcion) from Radix et Rhizoma Rhei. Several important parameters influencing the extraction efficiency of TA IL-DLLME such as the type and volume of extraction solvent and disperser solvent, sample pH, extraction time, extraction temperature, centrifugation time as well as salting-out effects were optimized. Under the optimal conditions, the spiked recovery for each analyte was in the range of 95.2-108.5%. The precisions of the proposed method were varied from 1.1% to 4.4% (RSD). All the analytes exhibited good linearity with correlation coefficients (r²) ranging from 0.9986 to 0.9996. The limits of detection for all target analytes were ranged from 0.50 to 2.02 μg L⁻¹ (S/N = 3). The experimental results indicated that the proposed method was successfully applied to the analysis of anthraquinones in Radix et Rhizoma Rhei.