Determination of Trace Chloroanilines in Environmental Water Samples Using Hollow Fiber-Based Liquid Phase Microextraction

A liquid phase microextraction method using hollow fiber to support extraction solvent was developed for enrichment of trace level chloroanilines in environmental water samples. Target analytes, 2-chloroaniline, 3-chloroaniline, 2,3-dichloroaniline, 2,4-dichloroaniline, 3,4-dichloroaniline, and 3,5-dichloroaniline were determined using gas chromatography-flame ionization detector after extraction. Experimental conditions that affect extraction efficiency were investigated and optimized. The proposed method showed a wide linear range from lower ??g L^?1 to 1,000 ??g L^?1, low detection limits (??5.1 ??g L^?1), and reasonable relative standard deviations (RSDs < 13%). Feasibility of the method was evaluated by analyzing river water samples collected from the Hudson River and the East River in New York City.     

Application of vortex-assisted supramolecular solvent liquid–liquid microextraction for trace determination of nitroaniline isomers

A novel, fast and efficient method for the analysis of nitroaniline isomers as model compounds was developed using vortex-assisted supramolecular solvent liquid–liquid microextraction (VA-SMS-LLME). A vortex mixer was used as the mixer in supramolecular solvent liquid–liquid microextraction, and it decreased the extraction time greatly. Several important parameters influencing extraction efficiency, such as the type and volume of extraction solvent, pH of sample, salt effect and extraction time, were optimised in detail. Under the optimal conditions, the enrichment factor was 133 for p-nitroaniline, 98 for m-nitroaniline and 115 for o-nitroaniline, and the limits of detection by HPLC were 0.3, 1.0 and 0.5 μg L^?1, respectively. Linearity with determination coefficient from 0.9981 to 0.9993 was evaluated using water samples spiked with the nitroanilines at fourteen different concentration ranging from 4 to 1000 μg L^?1. The ranges of intra-day and inter-day precision (n = 5) at 10 μg L^?1 of nitroanilines were 1.67–7.05% and 9.4–11.6%, respectively. The VA-SMS-LLME method was successfully applied for preconcentration of nitroanilines in environmental water samples.     

Magnetic Stirring-Assisted Dispersive Suspended Microextraction with Solidification of a Floating Organic Droplet for the Determination of Trace Fungicides in Water and Wine

For the first time, a simple method for magnetic stirring-assisted dispersive suspended microextraction has been developed for the determination of three fungicides (azoxystrobin, diethofencarb, and pyrimethanil) in water and wine samples. The method is based on the solidification of a floating organic droplet coupled with high performance liquid chromatography. In the proposed method, the low toxicity solvent 1-dodecanol was used as the extractant. Both the extraction and phase separation process were performed with magnetic stirring. No centrifugation step was involved. After separating the two phases, the extraction solvent droplet was easily collected through solidification at lower temperature. Important parameters such as the kind and volume of organic extraction solvent, extraction and restoration speed, extraction and restoration time, and salt concentration were optimized. Under the optimal conditions, the limits of detection for the analytes varied from 0.14 to 0.26 µg L^?1. The enrichment factors ranged from 125–200. The linearity ranges were 1–2000 µg L^?1, yielding correlation coefficients (r) higher than 0.9990. The relative standard deviation (n = 6) at two spiked level of 0.2 µg mL^?1 and 4 µg L^?1 varied between 2.2% and 7.8%. Finally, the developed technique was successfully applied to determine target fungicides in real water and wine samples, where the obtained recoveries ranged from 83.8–105.3%     

Use of ionic liquid based chitosan as sorbent for preconcentration of fluoroquinolones in milk,egg, fish,bovine, and chicken meat samples by solid phase extraction prior to HPLC determination

The possibility of using ionic liquid based chitosan sorbent for the separation and preconcentration of fluoroquinolone antibiotics (marbofloxacin, enoxacin, ofloxacin, ciprofloxacin, and enrofloxacin) has been studied. For this reason, different ionic liquids were prepared and coated on the chitosan sorbent. The conditions of the preconcentration of fluoroquinolones on a microcolumn have been optimized and the extraction efficiencies of the prepared sorbents have been compared. The compounds were eluted with 5 mL of 20% NH₃ (v/v, MeOH) solution and determined by HPLC with diode array and fluorescence detector. The limits of detection were found as 4.23 µ g L^?1 for marbofloxacin, and 1.09 µg L^?1 for enoxacin; 3.23 × 10^?3 µg L^?1 for ofloxacin; 8.39 × 10^?3 µg L^?1 for ciprofloxacin; and 19.50 × 10^?3 µg L^?1 for enrofloxacin. The developed method was applied for the analysis of fluoroquinolone in milk, egg, fish, bovine, and chicken samples and the recoveries were obtained in the range 70–100%.     

Determination of Organotin Compounds in Wine by Microwave-Assisted Extraction and High Performance Liquid Chromatography–Inductively Coupled Plasma Mass Spectrometry

A new analytical procedure for the determination of five organotin compounds in several matrix wine samples is reported. The organotin compounds were extracted by microwave-assisted extraction with n-hexane. Extraction conditions, such as volume of n-hexane required, extraction temperature, and extraction time, were investigated and optimized by an orthogonal array experimental design. The determination of organotin compounds in the final extracts was carried out by liquid chromatography–inductively coupled plasma mass spectrometry. The procedure showed limits of detection between 0.029–0.049 µg · L^?1. The linearity was in the range of 0.5 to 100 µg · L^?1. The precision expressed as relative standard deviation (RSD) was below 9.43%. The developed method was successfully employed to analyze different matrix wine samples, and some analytes were detected at the level of 0.053 to 1.14 µg · L^?1.     

Preconcentration and determination of low amounts of cobalt in black tea,paprika and marjoram using dispersive liquid–liquid microextraction and flame atomic absorption spectrometry

A dispersive liquid–liquid microextraction (DLLME) method for separation/preconcentration of ultra trace amounts of Co(II) and its determination with FAAS was developed. The DLLME behavior of Co(II) using Aliquat 336-chloride as ion pairing agent was systematically investigated. The factors influencing the ion pair formation and extraction by DLLME method were optimized. Under the optimized conditions for 150 µL of extraction solvent (carbon tetrachloride), 1.5 mL disperser solvent (acetonitrile) and 5 mL of sample, the enrichment factor was 30. The detection limit was 5.6 µg L^?1 and the RSD for replicate measurements of 1 mg L^?1 was 1.32 %. The calibration graph using the preconcentration system for cobalt was linear from 40 to 400 µg L^?1 with a correlation coefficient of 0.999. The proposed method was successfully applied for determination of cobalt in black tea, paprika and marjoram real samples.     

Magnetic Multi-Walled Carbon Nanotubes Matrix Solid-Phase Dispersion with Dispersive Liquid–Liquid Microextraction for the Determination of Ultra Trace Bisphenol A in Water Samples

Magnetic nanoparticle-assisted solid-phase dispersion (MMSPD) combined with dispersive liquid–liquid microextraction (DLLME) prior to high performance liquid chromatography with fluorescence detector (HPLC–FLU) is presented for determination of ultra trace Bisphenol A (BPA) in water. Magnetic multi-walled carbon nanotubes (MMWCNTs) were synthesized for the adsorption of BPA in water. Ultra trace BPA in water was transferred into the elute solvent by the MMSPD and further concentrated into trace volume extraction solvent by the DLLME. The limit of detection and limit of quantitation were 0.003 and 0.01 µg L^?1, respectively. Good linearity of BPA was found, ranging from 0.01 to 10 µg L^?1, with good squared regression coefficient (R ²) of 0.9999. Additionally, relative recoveries were 83.1 and 95.9% for two environmental water samples spiked with 0.20 µg L^?1 BPA, respectively. All results showed that the MMWCNTs nanoparticle-assisted MMSPD–DLLME–HPLC–FLU method was simple and reliable for the determination of ultra trace BPA in environmental water.     

Determination of Estrogens in Water Samples by Ionic Liquid-Based Dispersive Liquid-Liquid Microextraction Combined with High Performance Liquid Chromatography

Using 1-hexyl-3-methylimidazolium hexafluorophosphate ([C₆MIM][PF₆]) ionic liquid as extraction solvent, five estrogens including estrone (E₁), 17β-estradiol (E₂), estriol (E₃), 17α -ethynylestradiol (EE₂), and diethylstilbestrol (DES) in water samples were determined by dispersive liquid-liquid microextraction (DLLME) followed by high performance liquid chromatography with a photodiode array detector and a fluorescence detector (HPLC-DAD-FLD). The extraction procedure was induced by the formation of cloudy solution, which was composed of fine drops of [C₆MIM][PF₆] dispersed entirely into the sample solution with the help of a disperser solvent (acetone). Parameters including both extraction and disperser solvents and their volumes, extraction and centrifugal time, sample pH, and salt effect were investigated and optimized. Under the optimized conditions, 110–349 fold enrichment factors of analytes were obtained. The calibration curves were linear in the concentration range of 0.2–100 µg L^?1 for E₂, E₃, and EE₂ detected with FLD, and 1–100 µg L^?1 for E₁ and DES detected with DAD. The correlation coefficient of the calibration curve was between 0.9990 and 0.9997. The limits of detection (LOD, S/N = 3) for the five estrogens were in the range of 0.08–0.5 µg L^?1. The relative standard deviations (RSD) for six replication experiments at the concentration of 5.0 µg L^?1 were ≤5.7%. The proposed method was applied to the analysis of three water samples from different sources (river water, waste water, and sea water). The relative recoveries of spiked water samples are satisfied with 89.3–102.4% and 88.7–105.2% at two different concentration levels of 5.0 and 50.0 µg L^?1, respectively.     

Dabsyl chloride derivatisation of melamine followed by high-performance liquid chromatography determination in water samples

A new and sensitive precolumn derivatisation with dabsyl chloride was developed for the analysis of melamine in water samples by high-performance liquid chromatography (HPLC) with visible detection. Derivatisation with dabsyl chloride leads to improving sensitivity and hydrophobicity of melamine. Under optimum conditions of derivatisation and microextraction, the method yielded a linear calibration curve ranging from 10 to 2000 µg L^?1 with a determination coefficient (R²) of 0.9952. Limit of detection (LOD) and limit of quantification (LOQ) were 2.0 and 6.0 µg L^?1, respectively. The relative standard deviation per cent (RSD%) for intraday and inter-day extraction and determination at 20 and 200 µg L^?1 levels of melamine was less than 8.2% (n = 6). Finally, the proposed method was successfully applied for the determination of melamine in different water samples and satisfactory results were obtained (relative recovery ≥91%).     

Custom-Made C18 Column for Simultaneous Determination of Endocrine Disrupting Substances in Water by Diode-Array and Fluorescence Detectors

A C₁₈ stationary phase was synthesized for a custom-made HPLC column. When compared to a commercial C₁₈ column, better chromatographic performances were obtained. This column was successfully applied for simultaneous determination of p,p′-DDT, o,p′-DDT, benzo(a)anthracene, benzo(b)fluoranthene, and benzo(a)pyrene in waters by high performance liquid chromatography coupled with dual detectors (diode array and fluorescence detectors) combined with solid phase extraction. Low method detection limits were obtained, i.e., p,p′-DDT: 0.5 µg L^?1, o,p′-DDT: 1 µg L^?1, benzo(a)anthracene: 2.5 ng L^?1, benzo(b)fluoranthene: 5 ng L^?1, and benzo(a)pyrene: 2.5 ng L^?1. High recoveries that ranged from 82 to 94% were obtained for all compounds.     

Evaluation of the Counter Ions in Doped Porous Polyaniline Coatings on Stainless Steel Wires for Solid Phase Microextraction of Chlorophenolics in Water Combined with High-Performance Liquid Chromatography

Porous polyaniline coatings doped with different counter ions were electrodeposited on the surface of stainless steel wires using controlled potentiostatic coulometry. Prior to electropolymerization, the stainless steel wires were chemically etched to improve subsequent immobilization of the polyaniline coatings on the substrate and to increase the effective surface area. Porous polyaniline coatings doped with sulfate, nitrate, and perchlorate counter ions were employed for solid-phase microextraction (SPME) of 2-chlorophenol, 2,4-dichlorophenol, triclosan, and 2,4-dichlorophenoxyacetic acid coupled to high-performance liquid chromatography. The results demonstrated that the perchlorate doped polyaniline coating exhibited the highest extraction efficiency for 2-chlorophenol, 2,4-dichlorophenol, and triclosan at pH 5.0, indicating that the extraction capability was modified by introducing different counter ions into the coatings. As a result, the perchlorate doped polyaniline coated fiber was further used for the optimization of extraction condition s . The method provided linear dynamic ranges over 2 to 4 orders of magnitude. The limits of detection were 0.006 µg · L^?1, 0.005 µg · L^?1, and 0.040 µg · L^?1 for 2-chlorophenol, 2,4-dichlorophenol, and triclosan, respectively. The precision expressed as the relative standard deviation ranged from 2.20% to 5.04% for spiked water at 10 µg · L ^?1 (n = 5) and the fiber to fiber reproducibility was between 3.27% and 5.91% (n = 5). The method was successfully applied to the determination of chlorophenolics in real water samples. The recoveries of chlorophenolics in spiked water at 5.0 µg · L^?1 were between 99.60% and 108.7% with relative standard deviations between 3.24% and 5.47%.     

Determination of five polar herbicides in water samples by ionic liquid dispersive liquid-phase microextraction

A simple, rapid and efficient ionic liquid based on dispersive liquid-phase microextraction (IL-DLPME) method was developed for the determination of three triazine and two phenylurea herbicides in water samples. IL (1-hexyl-3-methylimidazolium hexafluorophosphate [C₆MIM][PF₆]) that dispersed completely into the water solution under controlled temperature was used as the extraction solvent. The analytes were easily concentrated into the ionic liquid phase. This technique combined the process of extraction and concentration of the analytes into one step and avoided use of the more common, toxic organic solvents. The factors affecting the extraction efficiency such as the IL volume, sample pH, extraction time, centrifugal time, dissoluble temperature and ionic strength were optimized. The extracts were analyzed by high-performance liquid chromatography (HPLC) coupled with diode array detector (DAD). Under the optimized conditions, recoveries (50.5–109.1%) were obtained for the target analytes in water samples. The calibration curves were linear and the correlation coefficient ranged from 0.9947 to 0.9973 in the concentration levels of 5–100 μg L^?1. The relative standard deviations (RSDs, n?=?5) were 6.80–10.78%. The limit of detections (LODs) for the five polar herbicides were between 0.46 μg L^?1 and 0.89 μg L^?1.     

Liquid–Liquid Microextraction of Nitrophenols Using Supramolecular Solvent and Their Determination by HPLC with UV Detection

A novel, efficient, and environmentally friendly method—supramolecular solvent liquid–liquid microextraction (SMS-LLME) combined with high-performance liquid chromatography (HPLC)—was first established for the determination of p-nitrophenol and o-nitrophenol in water samples. Several important parameters influencing extraction efficiency, such as the type and volume of extraction solvent, pH of sample, temperature, salt effect, extraction time, and stirring rate, were optimized in detail. Under the optimal conditions, the enrichment factor was 166 for p-nitrophenol and 160 for o-nitrophenol, and the limits of detection by HPLC were 0.26 and 0.58 μg L^?1, respectively. Excellent linearity with coefficients of correlation from 0.9996 to 0.9997 was observed in the concentration range of 2–1,000 μg L^?1. The ranges of intra- and interday precision (n = 5) at 100 μg L^?1 of nitrophenols were 5.85–7.76 and 10.2–11.9 %, respectively. The SMS-LLME method was successfully applied for preconcentration of nitrophenols in environmental water samples.     

Flow Injection Chemiluminescence Determination of Retinol and α-Tocopherol in Blood Serum and Pharmaceuticals

A simple and sensitive flow-injection method is reported for the determination of retinol and α-tocopherol in human blood serum and pharmaceuticals. The method is based on the reduction of vanadium(V) by retinol and α-tocopherol and subsequent reaction of reduced vanadium with luminol to generate chemiluminescence signal. The optimized conditions allow a linear calibration range of 30–2850 µg L^?1 and 5–4300 µg L^?1 for retinol and α-tocopherol, with relative standard deviations of 1.2–4.6% and 1.5–5.6%, respectively. The detection limits for retinol and α-tocopherol, defined as three times the standard deviation of measured blanks were 23 µg L^?1 and 2.15 µg L^?1, respectively. The proposed method allowed up to 20 determinations h^?1. The tolerance amount of foreign ions/compounds on the determination of retinol and α-tocopherol was also examined. The method was applied to the determination of retinol and α-tocopherol in human blood serum and pharmaceutical samples using hexane extraction with recoveries in the range of 92 ± 2 to 96 ± 1%, and the results obtained were compared with HPLC reference method.     

Polypropylene-Based Microextraction Method for Determination of Fluoxetine in Human Urine Samples

A polypropylene (PP) sheet was successfully applied as an extracting medium for trace enrichment of fluoxetine (FLX) from urine samples, followed by high performance liquid chromatography-fluorescence detection (HPLC-FD). The extraction medium was a square, 1 × 1 cm² piece of polypropylene membrane sheet that was conditioned in methanol. The extraction process was conveniently carried out using a 5 mL urine sample. After extraction, the PP sheet was withdrawn and transferred to a glass vial for performing the desorption process using 210 µL organic solvent. After complete drying, the residue was dissolved in 50 µL of methanol and an aliquot of 20 µL was, finally, injected into the HPLC system. Some important extraction parameters such as desorption solvent, pH, ionic strength, desorption, and extraction time were investigated and optimized. The linearity was studied by preconcentration of 5 mL of urine sample spiked with a standard solution of fluoxetine at the concentration range of 10–100 µg L^?1. The coefficient of determination was satisfactory (r² > 0.99). The relative standard deviations (RSD %) value under the optimized condition was found to be 10.3%. The limit of detection (LOD) and limit of quantification (LOQ) were 1.9 and 6.4 µg L^?1, respectively. The developed method showed to be simple, sensitive, and adequate for the trace determination of fluoxetine in urine media.     

The separation–preconcentration and determination of ultra-trace gold in water and solid samples by dispersive liquid–liquid microextraction using 4-ethyl-1(2-(4-(4-nitrophenyl)piperazin-1-yl)acetyl)thiosemicarbazide) as chelating agent and flame atomic absorption spectrometry

A selective separation and preconcentration method for the determination of gold ions in water and ore samples has been developed using dispersive liquid–liquid microextraction, followed by flame atomic absorption spectrometry. 4-Ethyl-1(2-(4-(4-nitrophenyl)piperazin-1-yl)acetyl)thiosemicarbazide) (NPPTSC) has been used for the first time as new chelating reagent. A mixture of ethanol (dispersive solvent) and carbon tetrachloride (extraction solvent) was used. Some parameters affecting the extraction procedure including the type and volume of the extracting and dispersive solvents, HNO₃ concentration, the chelating agent amount, volume of sample, and foreign ions have optimized. Also, the complex formation between gold ions and the ligand has been investigated in a methanol–water solution (1:1) using UV–visible spectrometry. The spectrophotometric titration data showed that of Au–NPPTSC complex composition was found to be 3:2. After optimizing the instrumental and experimental parameters, we achieved a detection limit of 1.5 µg L^?1, a preconcentration factor of 50, and a linear dynamic range of 10.0–400.0 µg L^?1. The relative standard deviation obtained 2.1% at 50 µg L^?1 for gold ions (n = 10). The proposed method was successfully performed for the determination of gold in certified reference material, environmental water, and ore samples.     

Dispersive Liquid–Liquid Microextraction of Silver Prior to Determination by Microsample Introduction-Flame Atomic Absorption Spectrometry

Abstract

A new simple and sensitive method has been proposed for rapid determination of trace levels of silver in environmental water samples, using dispersive liquid–liquid microextraction (DLLME) prior to its microsample introduction-flame atomic absorption spectrometry. Under the optimum conditions, the linear range was 0.1–7 µg L^?1 and limit of detection was 0.018 µg L^?1. The relative standard deviation for 0.50 and 5.00 µg L^?1 of silver in water sample was 4.0 and 1.7%, respectively. The relative recoveries of silver from tap, well, river, and seawater samples at spiking levels of 1.00 and 5.00 µg L^?1 were in the range of 86.4–98.6%.     

Hollow Fiber/Solvent Bar Microextraction Coupled with High Performance Liquid Chromatography for Preconcentration and Determination of Tanshinones and Salvianolic Acids in Radix Salvia miltiorrhiza

Hollow fiber solvent bar microextraction coupled with high-performance liquid chromatography was developed for the preconcentration and determination of active ingredients in Radix Salvia miltiorrhiza. These ingredients include dihydrotanshinone I, cryptotanshinone, tanshinone I, tanshinone IIA, salvianolic acid B, danshensu, and protocatechuic aldehyde. To evaluate the technique, seven compounds of varying polarity were used as model analytes, and a polyvinylidene fluoride hollow fiber (1.0 cm) with octanol (2 µL) was used as microextraction bar. The extraction conditions, including the identity of the hollow fiber, organic solvent, pH, salt addition, agitation speed, extraction time, and volume, were investigated and optimized. The extraction mechanism was analyzed and verified. The two main parameters, extraction recovery and enrichment factor, were obtained. Under the most favorable conditions, the enrichment factors of the analytes were 0.7–612, the limits of detection were below 1.11 ng mL^?1, and the recoveries were between 95.4% and 101.3%. Thus, hollow fiber solvent bar microextraction is simple, rapid, and practical with a wide range of potential applications.     

Analysis of PAHs in Water and Fruit Juice Samples by DLLME Combined with LC-Fluorescence Detection

A simple, rapid and efficient method termed dispersive liquid–liquid microextraction combined with liquid chromatography-fluorescence detection, has been developed for the extraction and determination of polycyclic aromatic hydrocarbons (PAHs) in water and fruit juice samples. Parameters such as the kind and volume of extraction solvent and dispersive solvent, extraction time and salt effect were optimized. Under optimum conditions, the enrichment factors ranged from 296 to 462. The linear range was 0.01–100 μg L^?1 and limits of detection were 0.001–0.01 μg L^?1. The relative standard deviations (RSDs, for 5 μg L^?1 of PAHs) varied from 1.0 to 11.5% (n = 3). The relative recoveries of PAHs from tap, river, well and sea water samples at spiking level of 5 μg L^?1 were 82.6–117.1, 74.9–113.9, 77.0–122.4 and 86.1–119.3%, respectively. The relative recoveries of PAHs from grape and apple juice samples at spiking levels of 2.5 and 5 μg L^?1 were 80.8–114.7 and 88.9–123.0%, respectively. It is concluded that the proposed method can be successfully applied for determination of PAHs in water and fruit juice samples.     

Preparation of a Robust and Sensitive Gold-Coated Fiber for Solid-Phase Microextraction of Polycyclic Aromatic Hydrocarbons in Environmental Waters

A robust gold-coated solid-phase microextraction fiber was rapidly prepared on an etched stainless-steel wire based on chemical deposition. Gold(III) was reduced to produce a mechanically robust fiber with a stable coating. Subsequently, it was applied for solid-phase microextraction of five polycyclic aromatic hydrocarbons in water samples coupled to high performance liquid chromatography with an ultraviolet-visible detector. The preconcentration conditions were optimized, including extraction and desorption time, temperature, stirring rate, and ionic strength. Under the optimized conditions, the calibration graphs were linear in the range from 1 to 500 µg · L^?1 for naphthalene and 0.20–500 µg · L^?1 for phenanthrene, anthracene, fluoranthene, and pyrene. Limits of detection were between 0.016 and 0.22 µg · L^?1 (signal-to-noise ratio = 3). The analysis of water samples showed that the recoveries ranged from 86.0% to 112.9% with relative standard deviations between 2.03% and 11.7%. The fiber coating was sensitive and suitable for the preconcentration and determination of polycyclic aromatic hydrocarbons in environmental waters. Compared with previously reported solid-phase microextraction methods, this device offered easy preparation, low cost, resistance to organic solvents, good stability, and high durability.