New method for microextraction of ultra trace quantities of gold in real samples using ultrasound-assisted emulsification of solidified floating organic drops

A method was developed for the determination of gold ion in water samples using microextraction based on the ultrasound-assisted emulsification of solidified floating organic drops, followed by the flame atomic absorption spectrometry. N-(4-{4-[(anilinocarbothioyl)amino]benzyl}phenyl)-N-phenylthiourea was used as chelating agent. The parameters affecting the extraction and complex formation (including the type and volume of the extracting solvent, time of sonication and centrifugation, pH, amount of the chelating agent, and sample ionic strength) were optimized. Under the optimum conditions, the calibration graph is linear in the range from 1.5 to 400 ng mL^?1, with a limit of detection of 0.45 ng mL^?1. The relative standard deviation for ten replicate determinations of gold ion in a concentration of 175 ng mL^?1 was 1.7%. The procedure was successfully applied to the determination of gold in water samples, in pharmaceutical and synthetic samples, and in a standard reference material.

Ultrasound- assisted emulsification microextraction for separation of trace amounts of antimony prior to FAAS determination

We describe a simple and rapid method for the ultrasound-assisted microextraction of antimony using the solidified floating organic drop method. The effects of pH, type and volume of the extractant, time of sonication, amount of chelating agent, type and amount of surfactant were investigated and optimized. Bromopyrogollol red is acting as the chelating agent. Antimony(III) ion was extracted into finely dispersed droplets of undecanol after ion-pair formation with the water soluble chelator and the cationic detergent benzyldimethyltetradecylammonium chloride. Flame atomic absorption spectrometry was used for the detection. The resulting calibration is linear in the concentration range from 4.0 to 900?ng?mL^-1 of Sb(III) with a correlation coefficient of 0.9981. The enrichment factor is 67, the detection limit is 0.62?ng?mL^-1, and the relative standard deviation is?±?3.6% (at 100?ng?mL^-1; for n?=?10). The method was successfully applied to the determination of antimony in water samples.

Determination of Se(IV) using solidified floating organic drop microextraction coupled to ultrasound-assisted back-extraction and hydride generation atomic fluorescence spectrometry

A method is presented for matrix separation, preconcentration and determination by hydride generation atomic fluorescence spectrometry of trace amounts of Se(IV). It is based on solidified floating drops of 1-undecanol that are capable of extracting the target analyte after chelation with a water soluble ligand and subsequent ultrasound-assisted back-extraction into a aqueous solution. Hydride generation was then accomplished by reaction with a solution of sodium borohydride. Under optimized conditions, an enrichment factor of 15 and a linear calibration plot in the range from 0.01 to 5.0 μg L^?1 were achieved using a 10.0 mL sample. The detection limit (3σ) is 7.0 ng L^?1, and the relative standard deviation (RSD) is 2.1% at 1.0 μg L^?1 (n?=?11). The method was applied to determination of Se(IV) in different real water samples through recovery experiments and subsequently validated against two certified reference materials.

Dispersive liquid-liquid microextraction of phenolic compounds using solidified floating organic droplets, and their determination by HPLC

We have developed a simple and efficient method for dispersive liquid-liquid microextraction of 4-nitrophenol, 2-naphthol and bisphenol A in real water samples. It is making use of solidified floating organic droplets of 1-dodecanol which has low density and a proper melting point. The type and volume of extraction solvent and dispersive solvent, the effect of salts, pH value and extraction time were optimized and resulted in enrichment factors of 84 for 4-nitrophenol, 123 for 2-naphthol, and 97 for bisphenol A. The limits of detection by HPLC are 1.50, 0.10 and 1.02 ng · mL^?1, respectively. Excellent linearity is observed in the concentration range from 10 to 800 ng · mL^?1, with coefficients of correlation ranging from 0.9988 to 0.9999. The relative standard deviations (for n?=?5) are from 3.2 to 5.3 %, and relative recoveries for the three phenols in tap, river and spring water range from 85.0 to 105.0 %, 98.3 to 110.0 %, and 98.6 to 109.0 %, respectively.

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.

Determination of the rare earth elements La, Eu, and Yb using solidified floating organic drop microextraction and electrothermal vaporization ICP-MS

We have developed a method for the determination of trace levels of the rare earth elements La, Eu, and Yb in biological and environmental samples. It is based on solidified floating organic drop microextraction using 1-(2-pyridylazo)-2-naphthol (PAN) as a chelator, followed by electrothermal vaporization (ETV) and quantification by inductively coupled plasma mass spectrometry. PAN also acts as a modifier in ETV. The effects of pH, amount of PAN, extraction time, stirring rate, volume of sample solution, and temperature program were examined. Under optimized conditions, the detection limits are 2.1, 0.65 and 0.91 pg mL^?1 for the elements La, Eu and Yb, respectively. The relative standard deviations are <6.0 % (c?=?0.1 ng mL^?1, n?=?9). When applied to the analysis of (spiked) natural water samples, the recoveries range from 92 to 105 %. The accuracy was validated with certified reference materials (combined sample of branch and leaf of shrub: GBW 07603 and human hair: GBW 07601), and the results were in good agreement with the certified values.

In-situ ionic liquid-dispersive liquid-liquid microextraction method to determine endocrine disrupting phenols in seawaters and industrial effluents

We have evaluated an in-situ ionic liquid-dispersive liquid-liquid microextraction procedure for the determination of six endocrine disrupting phenols in seawaters and industrial effluents using HPLC. The optimized method requires 38???L of the water-soluble ionic liquid 1-butyl-3-methylimidazolium chloride, and 5?mL of seawater or industrial effluent. After appropriate work-up, a drop (~10???L) of an ionic liquid is formed that contains the analytes of interest. It is diluted with acetonitrile and injected into the HPLC system. This procedure is accomplished without heating or cooling the solutions. The method is characterized by (a) average relative recoveries of 90.2%, (b) enrichment factors ranging from 140 to 989, and (c) precisions (expressed as relative standard deviations) of less than 11% when using a spiking level of 10?ng?mL^?1. The limits of detection range from 0.8?ng?mL^?1 for 4-cumylphenol to 4.8?ng?mL^?1 for bisphenol-A.

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.

Analysis of dextromethorphan and pseudoephedrine in human plasma and urine samples using hollow fiber-based liquid–liquid–liquid microextraction and corona discharge ion mobility spectrometry

We report on the use of hollow fiber liquid-liquid-liquid microextraction (HF-LLLME) followed by corona discharge ion mobility spectrometry for the determination of dextromethorphan and pseudoephedrine in urine and plasma samples. The effects of pH of the donor phase, stirring rate, ionic strength and extraction time on HF-LLLME were optimized. Under the optimized conditions, the linear range of the calibration curves for dextromethorphan in plasma and urine, respectively, are from 1.5 to 150 and from 1 to 100 ng mL^?1. The ranges for pseudoephedrine, in turn, are from 30 to 300 and from 20 to 200 ng mL^?1. Correlation coefficients are better than 0.9903. The limits of detection are 0.6 and 0.3 ng mL^?1 for dextromethorphan, and 8.6 and 4.2 ng mL^?1 for pseudoephedrine in plasma and urine samples, respectively. The relative standard deviations range from 6 to 8%.

Micro-scale quantitation of ten phthalate esters in water samples and cosmetics using capillary liquid chromatography coupled to UV detection: effective strategies to reduce the production of organic waste

We have extracted ten phthalate esters (C1 to C8) using six different micro-scale methods for extraction, and then separated them by capillary liquid chromatography coupled to UV detection. The methods included liquid-liquid extraction, ultrasonic-assisted extraction, microwave-assisted extraction, dispersive liquid-liquidmicroextraction, dispersive liquid-liquid microextraction solidification of floating organic droplets, and cloud point extraction. The linear range of the analytes is from 0.5 to 50 μg mL^?1, and the detection limits range from 0.02 to ~0.17 μg mL^?1. The precision and accuracy of all intra- and inter-day analyses are <5.5%. We find that dispersive liquid-liquid microextraction solidification of floating organic droplet (DLLME-SFO) is the best method for quantification of most phthalate esters in water samples and cosmetics because of its low limit of detection and high extraction efficiencies.

Ionic liquid based dispersive liquid-liquid microextraction combined with ICP-OES for the determination of trace quantities of cobalt, copper, manganese, nickel and zinc in environmental water samples

We describe a method for ionic liquid based dispersive liquid-liquid microextraction of Co(II), Cu(II), Mn(II), Ni(II) and Zn(II), followed by their determination via flow injection inductively coupled plasma optical emission spectrometry. The method is making use of the complexing agent 1-(2-thenoyl)-3,3,3-trifluoracetone, the ionic liquid 1-hexyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)imide, and of ethanol as the dispersing solvent. After extraction and preconcentration, the sedimented ionic liquid (containing the target analytes) is collected, diluted with 1-propanol, and introduced to the ICP-OES. Effects of pH, ionic strength, ligand to metal molar ratio, volumes of extraction and disperser solvents on the performance of the microextraction were optimized in a half-fractional factorial design. The significant parameters were optimized using a face-centered central composite design. The method has detection limits between 0.10 and 0.20?ng?mL^?1 of the metal ions, preconcentration factors between 79 and 102, linear responses in 0.25 to 200?ng?mL^?1 concentration ranges, and relative standard deviations of 3.4 to 6.0%. The method was successfully applied to the analysis of drinking water, a fish farming pond water, and waste water from an industrial complex.

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.

Mixed immunoassay design for multiple chemical residues detection

In this research, a mixed immunoassay design for multiple chemical residues detection based on combined reverse competitive enzyme-linked immunosorbent assay (ELISA) procedure was developed. This method integrated two reverse ELISA reactions in one assay by labeling horseradish peroxidase to deoxynivalenol (DON) and orbifloxacin. Within this method, IC50 of the two mAbs for each analyte we produced ranged from 23?～?68 ng?mL^?1 for DONs and 4.1?～?49 ng?mL^?1 for quinolones (QNs). The limit of detection measured by IC10 was achieved at 0.45–1.3 ng?mL^?1 for DONs and 0.59–6.9 ng?mL^?1 for QNs, which was lower than the maximum residue levels. Recoveries in negative samples spiked at concentrations of 100, 200, and 500 ng?mL^?1 ranged from 91.3 to 102.2 % for DONs and 88.7–98.05 % for QNs with relative standard deviation less than 9.88 and 12.67 %. The results demonstrated that this developed immunoassay was suitable for screening of low molecular weight contaminants.

Ionic liquid-based hollow fiber supported liquid membrane extraction combined with thermospray flame furnace AAS for the determination of cadmium

We have developed a simple and effective method for hollow fiber liquid-phase microextraction of cadmium. It is based on the use of a room temperature ionic liquid (RTIL) and was coupled to thermospray flame furnace AAS. The RTIL was placed in the pores of a polypropylene hollow fiber (acting as a liquid membrane) and also used as the acceptor solution. Ammonium pyrrolidinedithiocarbamate (APDC) was used as the chelating agent. The effects of the concentration of APDC, the pH of samples, stirring rates, extraction time, and potential interferences were optimized to result in a detection limit of 9?ng?L^?1 and an enrichment factor of 90. The relative standard deviation is 4.7% (at 0.5?ng?mL^?1, for n?=?5). The method was successfully applied to the determination of cadmium.

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.

Multiplex bead-array competitive immunoassay for simultaneous detection of three pesticides in vegetables

We report on a multiplex bead-based competitive immunoassay using suspension array technology for the simultaneous detection of the pesticides triazophos, carbofuran and chlorpyrifos. Three hapten-protein conjugates were covalently bound to carboxylated fluorescent microspheres to serve as probes. The amount of conjugates and antibodies were optimized. The new multi-analyte assay has dynamic ranges of 0.02–50 ng?mL^?1, 0.5–500 ng?mL^?1 and 1.0–1000 ng?mL^?1 for triazophos, carbofuran and chlorpyrifos, respectively, and the detection limits are 0.024, 0.93 and 1.68 ng?mL^?1. This new multiplex assay is superior to the traditional ELISA in possessing a wider detection range, better reproducibility and the feature of multi-target detection. Cross-reactivity studies indicated that the bead-array method is highly selective for the three target pesticides, and that individual analyses have no significant influence between each other, also without cross-reactions from other structurally related pesticides. The method was applied to analyze vegetables spiked with the three pesticides, and the recoveries were in ranges of 78.5–112.1 %, 72.2–120.2 % and 70.2–112.8 %, respectively, with mean coefficients of variation of <15 %.

A strategy to enhance the thermal stability of a nanostructured polypyrrole-based coating for solid phase microextraction

We report on a nanostructured self-doped polypyrrole (SPPy) film that was prepared by an electrochemical technique in an electrolyte containing fluorosulfonic acid as the sulfonation reagent. The film was applied as a new fiber material for solid-phase microextraction (SPME) of the pesticides lindane, heptachlor, aldrin, endosulfans I and II prior to their quantitation by GC with electron capture detection. The SPPy nanoparticles have a diameter of <100?nm. The introduction of covalently bound sulfo groups into the backbone of the polymer resulted in improved temperature resistance (~350?°C) and satisfactory extraction efficiency. The thermal stability of the SPPy fiber is superior to common polypyrrole fibers. Extraction was optimized by means of the Taguchi orthogonal array experimental design with an OA₁₆ (4⁵) matrix including extraction temperature, extraction time, salt concentration, stirring rate, and headspace volume. The method displays good repeatability (RSD?<?6%) and linearity (in the range from 0.78 to 100?ng?mL^?1; with an R² of >0.998. The detection limits are <0.23?ng?mL^?1. The method was successfully applied to the analysis of the pesticides in skimmed milk and fruit juice samples, and recoveries are from 84?±?1 to 105?±?1%.

Anodic stripping voltammetry of silver(I) using a carbon paste electrode modified with multi-walled carbon nanotubes

We describe a silver(I)-selective carbon paste electrode modified with multi-walled carbon nanotubes and a silver-chelating Schiff base, and its electrochemical response to Ag(I). Effects of reduction potential and time, accumulation time, pH of the solution and the stripping medium were studied by differential pulse anodic stripping voltammetry and optimized. The findings resulted in a method for the determination of silver over a linear response range (from 0.5 to 235 ng?mL^?1) and with a detection limit as low as 0.08 ng?mL^?1. The sensor displays good repeatability (with the RSD of ±?2.75 % for 7 replicates) and was applied to the determination of Ag(I) in water samples and X-ray photographic films.

Coupling polymer monolith microextraction to gas chromatography: determination of pyrethroids in water samples

A sensitive method has been established for the determination of the pyrethroids (fenpropathrin and permethrin) in water samples. It is based on microextraction using monoliths composed of a poly-(glycidyl methacrylate-co-ethylene dimethacrylate) copolymer, and on detection by gas chromatography coupled to electron-capture detection. Experimental parameters including the flow rate and volume of the samples, the type, volume and flow rate of eluent and effect of salt addition were optimized. The limits of detection for fenpropathrin and permethrin are 0.5 and 2.7?ng?mL^?1, respectively. The intra-day and inter-day precisions were less than 5.5% and 9.0%. The method was successfully applied to determination of two pyrethroids in the tap and lake water samples and the accuracy was evaluated by recovery experiments.

A cloud point extraction for spectrophotometric determination of ultra- trace antimony without chelating agent in environmental and biological samples

We report on a simple, sensitive and reliable method for the cloud point extraction of antimony (Sb) and its subsequent spectrophotometric detection. It is based on the color reaction of Sb (III) with iodide in acidic medium and subsequent micelle-mediated extraction of tetraiodoantimonate using a non-ionic surfactant in the absence of any chelating agent. The effects of reaction and extraction parameters were optimized. The calibration plot is linear in the range of 0.80–95?ng?mL^?1 of antimony in the sample solution, with a regression coefficient (r) of 0.9994 (for n?=?9). The detection limit (at SNR?=?3) is 0.23?ng?mL^?1, and the relative standard deviations at 10 and 70?ng?mL^?1 of antimony are 3.32 and 1.85?% (at n?=?8), respectively. The method compared favorably to other methods and was applied to determine antimony in seawater, anti-leishmania drug (glucantime), and human serum.