Modified ionic liquid cold-induced aggregation dispersive liquid-liquid microextraction followed by atomic absorption spectrometry for trace determination of zinc in water and food samples

We report on a new method for the microextraction and determination of zinc (II). The ion is accumulated via ionic-liquid cold-induced aggregation dispersive liquid-liquid microextraction (IL-CIA-DLLME) followed by flame atomic absorption spectrometry (FAAS). The ionic liquid (IL) 1-hexyl-3-methylimidazolium hexafluorophosphate is dispersed into a heated sample solution containing sodium hexafluorophosphate as a common ion source. The solution is then placed in an ice-water bath upon which a cloudy solution forms due to the decrease of the solubility of the IL. Zinc is complexed with 8-hydroxyquinoline and extracted into the IL. The enriched phase is dissolved in a diluting agent and introduced to the FAAS. The method is not influenced by variations in the ionic strength of the sample solution. Factors affecting the performance were evaluated and optimized. At optimum conditions, the limit of detection is 0.18???g?L^?1, and the relative standard deviation is 3.0% (at n?=?5). The method was validated by recovery experiments and by analyzing a certified reference material and successfully applied to the determination of Zn (II) in water and food samples.

Determination of phenolic compounds in water samples by HPLC following ionic liquid dispersive liquid-liquid microextraction and cold-induced aggregation

We report on the determination of bisphenol A and 2-naphthol in water samples using ionic liquid cold-induced aggregation dispersive liquid-liquid microextraction combined with HPLC. Parameters governing the extraction efficiency (disperser solvent, volume of extraction and disperser solvent, pH, temperature, extraction time) were optimized and resulted in enrichment factors of 112 for bisphenol A and of 186 for 2-naphthol. The calibration curve was linear with correlation coefficients of 0.9995 and 0.9998, respectively, in the concentration range from 1.5 to 200?ng?mL^?1. The relative standard deviations are 2.3% and 4.1% (for n?=?5), the limits of detection are 0.58 and 0.86?ng?mL^?1, and relative recoveries in tap, lake and river water samples range between 100.1 and 108.1%, 99.4 and 106.2%, and 97.1 and 103.8%, respectively.

Determination of ppb-level phenol index using in-syringe dispersive liquid-liquid microextraction and liquid waveguide capillary cell spectrophotometry

We report on an in-syringe dispersive liquid-liquid microextraction (DLLME) technique and its application to the determination of the total phenol index in natural waters. Xylene was used as extraction solvent in combination with a mixture of acetonitrile and n-propanol as dispersion solvents. The analytical procedure consists of mixing the sample with buffer, reacting it with 4-aminoantipyrine and potassium hexacyanoferrate, DLLME, phase separation, and index quantification and was automated using the multisyringe flow injection analysis technique and takes 200?s only. DLLME was accomplished by aspiration of the mixture of extraction and dispersion solvents followed by the aqueous phases into the syringe at a high flow rate. Phase separation occurs due to aggregation of the floating extractant droplets (with their lower specific density) at the head of the syringe. The extractant containing the chromogenic reaction product is then pushed into an optical waveguide capillary cell and spectrophotometrically detected at 500?nm. Figures of merits include a low limit of detection (0.9?ppb), a preconcentration factor of 20, a linear dynamic range up to 140?ppb, and a general standard deviation of 3.1?%. The method enabled the concentration of phenols in well water samples to be determined with a mean recovery of 101?%.

Speciation of arsenite and arsenate by electrothermal AAS following ionic liquid dispersive liquid-liquid microextraction

We have developed a new method for the microextraction and speciation of arsenite and arsenate species. It is based on ionic liquid dispersive liquid liquid microextraction and electrothermal atomic absorption spectrometry. Arsenite is chelated with ammonium pyrrolidinedithiocarbamate at pH 2 and then extracted into the fine droplets of 1-butyl-3-methylimidazolium bis(trifluormethylsulfonyl) imide which acts as the extractant. As(V) remains in the aqueous phase and is then reduced to As(III). The concentration of As(V) can be calculated as the difference between total inorganic As and As(III). The pH values, chelating reagent concentration, types and volumes of extraction and dispersive solvent, and centrifugation time were optimized. At an enrichment factor of 255, the limit of detection and the relative standard deviation for six replicate determinations of 1.0 μg?L^?1 As(III) are 13 ng?L^?1 and 4.9 %, respectively. The method was successfully applied to the determination of As(III) and As(V) in spiked samples of natural water, with relative recoveries in the range of 93.3–102.1 % and 94.5–101.1 %, respectively.

Hydrogen peroxide sensor based on glassy carbon electrode modified with ��-manganese dioxide nanorods

A solid bar microextraction (SBME) method containing sorbent materials 2?mg in the lumen of a porous hollow fiber membrane 2.5?cm for the extraction of carbamazepine, diclofenac and ibuprofen from river water samples is described. The desorbed analytes were analyzed using reversed-phase high performance liquid chromatography with ultraviolet detection. In order to achieve optimum performance, several extraction parameters were optimized. Of the sorbents evaluated, LiChrosorb RP-8 was the most promising. Under the optimized conditions, limits of detection from 0.7 to 0.9???g?L^?1, precisions from 5.5 to 6.4% and a correlation coefficient of 0.999 were obtained for the target drugs over a concentration range of 1?C200???g?L^?1. In comparison with the solid phase extraction, the SBME system offers distinct advantages due to its higher enrichment factors, lower consumption of organic solvents and time saving.

Ionic liquid magnetic bar microextraction and HPLC determination of carbamate pesticides in real water samples

We have developed a simple method for the microextraction of the carbamate pesticides carbofuran, pirimicarb, and carbaryl. It is termed ionic liquid magnetic bar microextraction (ILMB-ME) and based on an ionic liquid deposited on a magnetic stirrer bar placed in a sealed short PCR tube into which microholes where pinned. When placed in a vial containing the aqueous sample solution, the ILMB tumbles freely in the aqueous solution and the carbamates are extracted into the ionic liquid phase which then was determined by HPLC. The enrichment factors for carbofuran, pirimicarb, and carbaryl are 107, 94, 95, respectively. The limits of detection, calculated as three times the signal-to-noise ratio (S/N), are 1.4?μg?L^?1 for carbofuran, 3.4?μg?L^?1 for pirimicarb, and 1.7?μg?L^?1 for carbaryl. The repeatability, carried out by extracting water samples spiked with carbamate levels of 200?μg?L^?1, yielded relative standard deviations between 2.9 and 6.0?%, (for n?=?5). The recoveries of all the three fungicides from tap, lake and rain water samples at spiking levels of 5 and 50?μg?L^?1 are in the range from 86 to 98?%, and from 80 to 96?%, respectively. We conclude that this is a simple, practical and efficient method for the determination of fungicide residues in real water samples.

Ultratrace determination of carbamate pesticides in water samples by temperature controlled ionic liquid dispersive liquid phase microextraction combined with high performance liquid phase chromatography

A simple and sensitive method was developed for the determination of three carbamate pesticides in water samples. It is based on temperature controlled ionic liquid dispersive liquid phase microextraction combined with high-performance liquid chromatography. The ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate was used as the extractant, and the factors affecting the extraction were investigated in detail. The detection limits obtained for isoprocarb, diethofencarb and fenothiocarb are 0.91, 0.45, and 1.40 μgL^-1, respectively, and the precisions are in the range between 1.0 and 1.8% (n?=?6). The method was validated with environmental water samples and the results indicate that it represents a viable alternative to existing methods.

Dispersive solid phase micro-extraction of dopamine from human serum using a nano-structured Ni-Al layered double hydroxide, and its direct determination by spectrofluorometry

We report on a simple method for dispersive solid-phase micro-extraction of dopamine (DA) from human serum. It is based on a layered double hydroxide (LDH) of nickel-aluminum, which acts as the extractant. DA is extracted at pH 8 using the LDH sol solution as a dispersed solid-phase extractor. The extracted DA is quantified by spectrofluorometry at 285?nm excitation and 315?nm emission wavelengths. A comparison of the fluorescence of DA in bulk solution and that of DA intercalated in the LDH revealed a nearly 5-fold improvement in intensity. Factors such as pH, concentration of LDH in the sol solution, and temperature were optimized. Under these conditions, the limit of detection is 0.015?μg?L^?1. The inter- and intra-day relative standard deviations for six replicate determinations of 1?μg?L^?1 DA were 1.7 and 1.1?%, respectively. The method was successfully applied to the determination of DA in human serum samples.

Simultaneous determination of carbazole-based explosives in environmental waters by dispersive liquid—liquid microextraction coupled to HPLC with UV-Vis detection

Dispersive liquid-liquid microextraction as a rapid, simple and efficient method coupled with high performance liquid chromatography-UV-Vis detection was used for sample preparation and subsequent determination of carbazole, tri nitro carbazole (TrNC) and tetra nitro carbazole in water samples. The influence of several important variables on the extraction efficiency has been evaluated. The methods works best with chloroform as an extractant and acetonitrile as the dispersive solvent. Under optimum conditions, the calibration curve is linear in the range from 0.007 to 1.75?μg?mL^?1 for TNC, 0.006 to 1.52?μg?mL^?1 for TrNC, and 0.008–2.10?μg?mL^?1 for carbazole. The limits of detection (LODs; at a signal-to-noise ratio of 3), range from 1.7 to 1.1?ng?mL^?1, for TNC, TrNC and carbazole. Also, the relative standard deviations (RSD, n?=?6) for the extraction of TNC (at 174?ng?mL^?1), TrNC (at 151?ng?mL^?1) and carbazole (at 84?ng?mL^?1) vary between 4.1 and 5.2%. The enrichment factors range from 179 to 186. The method was successfully applied to the determination of TNC, TrNC and carbazole in environmental samples.

In-situ ionic liquid-based microwave-assisted dispersive liquid–liquid microextraction of triazine herbicides

We report on the determination of the triazine herbicides ametryne, prometryne, terbuthylazine and terbutryn in water samples. The herbicides are extracted by in-situ ionic liquid-based microwave-assisted dispersive liquid-liquid microextraction and then determined by high-performance liquid chromatography. This is a new method for extraction that has the advantages of requiring less volume of ionic liquid (IL) than other methods and at the same time is quite fast. The type and volume of IL, the type and volume of disperser, irradiation temperature, extraction time and salt concentration were optimized. Figures of merit include linear regression coefficients between 0.9992 and 0.9995, acceptable recoveries (88.4–114?%), relative standard deviations of 1.6–6.2?%, and limits of detection between 0.52 and 1.3?μg?L^?1.

Surfactant-enhanced liquid-liquid microextraction coupled to micro-solid phase extraction onto highly hydrophobic magnetic nanoparticles

We are presenting a simplified alternative method for dispersive liquid-liquid microextraction (DLLME) by resorting to the use of surfactants as emulsifiers and micro solid-phase extraction (μ-SPE). In this combined procedure, DLLME of hydrophobic components is initially accomplished in a mixed micellar/microemulsion extractant phase that is prepared by rapidly mixing a non-ionic surfactant and 1-octanol in aqueous medium. Then, and in contrast to classic DLLME, the extractant phase is collected by highly hydrophobic polysiloxane-coated core-shell Fe₂O₃@C magnetic nanoparticles. Hence, the sample components are the target analyte in the DLLME which, in turn, becomes the target analyte of the μ-SPE step. This 2-step approach represents a new and simple DLLME procedure that lacks tedious steps such as centrifugation, thawing, or delicate collection of the extractant phase. As a result, the analytical process is accelerated and the volume of the collected phase does not depend on the volume of the extraction solvent. The method was applied to extract cadmium in the form of its pyrrolidine dithiocarbamate chelate from spiked water samples prior to its determination by FAAS. Detection limits were brought down to the low μg L^?1 levels by preconcentrating 10 mL samples with satisfactory recoveries (96.0–108.0 %).

Extraction of phthalate esters from water and beverages using a graphene-based magnetic nanocomposite prior to their determination by HPLC

We have developed a highly sensitive microextraction method for the preconcentration of some phthalate esters such as diethyl phthalate, di-n-propylphthalate, di-n-butyl-phthalate, dicyclohexyl-phthalate, and diethyl-hexyl phthalate prior to their determination by HPLC. It is based on a magnetic graphene nanocomposite as an effective adsorbent. The effects of the amount of the extractant composite employed, extraction time, pH values, salt concentration and desorption conditions were investigated. Under the optimum conditions, the enrichment factors range from 1574 to 2880. Response is linear in the concentration range from 0.1 to 50?ng?mL^?1. The limits of detection (at S/N?=?3) were between 0.01 and 0.04?ng?mL^?1. The method was successfully applied to the determination of five phthalate esters in water and beverage samples.

Extraction and determination of polybrominated diphenyl ethers in water and urine samples using solidified floating organic drop microextraction along with high performance liquid chromatography

We have developed a method, termed solidification of floating organic drop microextraction (SFOME), for the extraction of polybrominated diphenyl ethers (PBDEs) in water and urine samples, this followed by quantification via HPLC. This method requires very small quantities of organic solvent consumption. It is based on exposing a floating solidified drop of an organic solvent on the surface of aqueous solution in a sealed vial. The organic drop is easily collected with a spatula, molten (at ambient temperature), and then submitted to HPLC. Experimental parameters including extraction solvent and its volume, disperser solvent and its volume, extraction time, ionic strength, stirring speed and extraction temperature were optimized. The enrichment factors of analytes are in the range from 921 to 1,462, and acceptable extraction recoveries (92%–118%) are obtained. The dynamic linear range for five PBDE congeners is in the range of 0.5–75?μg.L^?1 and from 5 to 500?μg.L^?1 for BDE 209. The correlation coefficients range from 0.9960 to 0.9999. The limits of detection (at S/N?=?3) for PBDE congeners vary between 0.01 and 0.04?μg.L^?1. This method has been successfully applied to detecting PBDEs in two environmental waters and in human urine.

Determination of triclosan and triclocarban in environmental water samples with ionic liquid/ionic liquid dispersive liquid-liquid microextraction prior to HPLC-ESI-MS/MS

A hydrophobic ionic liquid was finely dispersed in aqueous solution along with a hydrophilic ionic liquid. Following centrifugation, the two phases aggregate to form relatively large droplets. Based on this phenomenon, a method termed ionic liquid/ionic liquid dispersive liquid-liquid microextraction was developed. It was applied to the enrichment of triclosan (TCS) and triclocarban (TCC) from water samples prior to HPLC with electrospray tandem MS detection. The type and volume of the hydrophobic ionic liquid (the extraction solvent) and the hydrophilic ionic liquid (the disperser solvent), salt content, and extraction time were optimized. Under optimum conditions, the method gives a linear response in the concentration ranges from 0.5 to 100???g L^?1 for TCC and from 2.5 to 500???g L^?1 for TCS, respectively. The limits of detection are 0.23 and 0.35???g L^?1, and the repeatability is 5.4 and 6.4% for TCC and TCS, respectively. The method was validated with four environmental water samples, and average recoveries of spiked samples were in the range from 88% to 111%. The results indicate that the method is a promising new approach for the rapid enrichment and determination of organic pollutants.

Screen-printed electrode-based electrochemical detector coupled with in-situ ionic-liquid-assisted dispersive liquid–liquid microextraction for determination of 2,4,6-trinitrotoluene

A novel method is reported, whereby screen-printed electrodes (SPELs) are combined with dispersive liquid–liquid microextraction. In-situ ionic liquid (IL) formation was used as an extractant phase in the microextraction technique and proved to be a simple, fast and inexpensive analytical method. This approach uses miniaturized systems both in sample preparation and in the detection stage, helping to develop environmentally friendly analytical methods and portable devices to enable rapid and onsite measurement. The microextraction method is based on a simple metathesis reaction, in which a water-immiscible IL (1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, [Hmim][NTf₂]) is formed from a water-miscible IL (1-hexyl-3-methylimidazolium chloride, [Hmim][Cl]) and an ion-exchange reagent (lithium bis[(trifluoromethyl)sulfonyl]imide, LiNTf₂) in sample solutions. The explosive 2,4,6-trinitrotoluene (TNT) was used as a model analyte to develop the method. The electrochemical behavior of TNT in [Hmim][NTf₂] has been studied in SPELs. The extraction method was first optimized by use of a two-step multivariate optimization strategy, using Plackett–Burman and central composite designs. The method was then evaluated under optimum conditions and a good level of linearity was obtained, with a correlation coefficient of 0.9990. Limits of detection and quantification were 7 μg L^?1 and 9 μg L^?1, respectively. The repeatability of the proposed method was evaluated at two different spiking levels (20 and 50 μg L^?1), and coefficients of variation of 7 % and 5 % (n?=?5) were obtained. Tap water and industrial wastewater were selected as real-world water samples to assess the applicability of the method.

Analysis of trace amounts of chlorobenzenes in water samples: An approach towards the automation of dynamic hollow fiber liquid-phase microextraction

We have combined dynamic hollow fiber liquid-phase microextraction with GC and electron capture detection for the quantitative determination of five chlorobenzenes in water samples. Extraction is based on an automated dynamic extraction device called TT-tube extractor which consists of a polypropylene hollow fiber mounted inside a stainless steel tube. Toluene is used as the extraction solvent that fills the lumen and pores of the hydrophobic fiber and flows through the lumen of the fiber using a programmable syringe pump. The type of organic solvent, ionic strength, diameter of the TT-tube, sample volume, and the times for extraction and dwelling were optimized. Under optimum conditions, the method gives limits of detection as low as 10–100?ng?L^?1, a linear dynamic range of 0.05–100?μg?L^?1, and relative standard deviations of <7% (n?=?6). The preconcentration factor can be as large as 562–973. In an example for a practical application, the chlorobenzenes were successfully determined in environmental aqueous samples. The hollow fiber membrane can be used at least 20 times without any carry-over or loss in extraction efficiency. The system is inexpensive and convenient, and requires minimal manual handling.

Simultaneous determination of multi-class antibiotic residues in water using carrier-mediated hollow-fiber liquid-phase microextraction coupled with ultra-high performance liquid chromatography tandem mass spectrometry

A method has been developed for carrier-mediated hollow-fiber liquid-phase microextraction (HF-LPME) and enrichment of multiple classes of antibiotics in water samples. Eleven compounds (erythromycin, spiramycin, tilmicosin, sulfathiazole, sulfamethazine, sulfamerazine, oxytetracycline, tetracycline, ciprofloxacin, danofloxacin and enrofloxacin) from four important classes of antibiotics (of the macrolide, sulfonamide, tetracycline and quinolone type) have been simultaneously preconcentrated with one set of HF-LPME conditions, followed by determination by ultra-HPLC combined with electrospray ionization tandem mass spectrometry (UHPLC-MS/MS). Antibiotics can be determined at ng L^?1 levels using this highly sensitive and selective method. Parameters including immersion time, liquid membrane composition, sample pH, acceptor composition and extraction time were optimized to finally give detection limits in the 10?C250?ng?L^?1 range. Good linearity was achieved, with up to 156 times enrichment over the four classes of antibiotics. This multi-residue method enabled the simultaneous enrichment of all 11 multi-class antibiotics from spiked river water samples, with relative recovery between 79 and 118%.

Salt-assisted liquid-liquid microextraction of Cr(VI) ion using an ionic liquid for preconcentration prior to its determination by flame atomic absorption spectrometry

We report on the salt-assisted liquid-liquid microextraction of cationic complexes of Cr(VI) ion using the hydrophilic ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoraborate and potassium hydrogen phosphate. This is a novel, simple, non-toxic and effective technique for sample pretreatment technique that displays large extraction efficiency and represents a new platform where Cr(VI) is complexed with 1,5-diphenylcarbazide (DPC) in sulfuric acid medium. It was applied to the extraction of Cr(VI) in the form of the Cr(VI)-DPC complex prior to its determination by flame atomic absorption spectrometry. Cr(III) ion also can be determined by this procedure after oxidation to Cr(VI). Extraction is mainly affected by the amount of water-soluble IL, the kind and quantity of inorganic salts, by pH and the concentration of DPC. Calibration plots are linear in the range from 3 to 150?μg?L^?1 of Cr(VI), and the limit of detection is 1.25?μg?L^?1. The method was successfully applied to the speciation and determination of trace levels of Cr(III) and Cr(VI) in environmental water samples containing high levels of dissolved salts or food grade salts.

Microwave assisted headspace controlled-temperature single drop microextraction for liquid chromatographic determination of chlorophenols in aqueous samples

We report on an efficient one-step sample preconcentration technique by coupling microwave heating and cloud vapor zone (CVZ)-based headspace controlled-temperature single drop microextraction (HS-CT-SDME), and its application to headspace extraction of chlorophenols in aqueous solutions. Microwave irradiation is utilized to accelerate evaporation of analytes into the headspace sampling zone for the direct extraction of aqueous chlorophenols. A microdrop of extractant is suspended at the bottom of a bell-mouthed micropipette tip connected to a microsyringe needle. An external cooling system was adopted to control the formation of the CVZ around the SDME tip in the headspace sampling area. In the CVZ procedure, the warm headspace vapor is quickly cooled near the SDME tip, thus forming a dense cloud of analyte-water vapor; thereby enhancing the partition of the analytes into the SDME solvent. The chlorophenols are then determined by LC-UV detection. Under the optimized experimental conditions, the analytical signal is linearly related to the concentration of the chlorophenols range of 2.5–250?ng?mL^?1. The detection limits vary from 0.3 to 0.7?ng?mL^?1, and the precision (expressed as the relative standard deviation) from 3.7 to 13.3?%. The method was validated with real water samples, and the spiked recovery ranged between 92 and 103.1?% for river water, and between 85.1?% and 98.6?% for lake water. Compared to other methods, microwave assisted HS-CT-SDME is simple, rapid, sensitive, inexpensive and eco-friendly, and requires less sample and organic extractant.

Supramolecular�Cbased dispersive liquid�Cliquid microextraction: A novel sample preparation technique for determination of inorganic species

A new simple and sensitive method has been developed for the determination of trace levels of inorganic species in environmental water samples. It is based on the use of supramolecular?Cbased dispersive liquid?Cliquid microextraction (SM?CDLLME) prior to microsample introduction into FAAS. The ions are micro?Cextracted with coacervates composed of reverse micelles made from decanoic acid and dispersed in tetrahydrofuran?Cwater mixtures. Cobalt ion was used as a model ion, and 1?C (2?Cpyridylazo)?C2?Cnaphthol as the complexing agent. SM?CDLLME results from a combination of DLLME with coacervation?Cbased microextraction. It combines the advantages of DLLME with those of preconcentration based on coacervation and reverse micelles. Factors affecting the extraction efficiency of Co and its subsequent determination by FAAS were optimized. Under the optimized conditions and using 5.00?mL sample only, the enhancement factor is 58, the limit of detection is 4.2???g L^?C1, and the relative standard deviations for 100???g L^?C1 and 30???g L^?C1 of Co are 2.1% and 3.8%, respectively (n?=?6). The accuracy of the method was confirmed by parallel analyses using the ASTM reference method.