Determination of triclosan,triclocarban and methyl-triclosan in aqueous samples by dispersive liquid–liquid microextraction combined with rapid liquid chromatography

In this study, dispersive liquid–liquid microextraction (DLLME) combined with ultra-high-pressure liquid chromatography (UHPLC)–tunable ultraviolet detection (TUV), has been developed for pre-concentration and determination of triclosan (TCS), triclocarban (TCC) and methyl-triclosan (M-TCS) in aqueous samples. The key factors, including the kind and volume of extraction solvent and dispersive solvent, extraction time, salt effect and pH, which probably affect the extraction efficiencies were examined and optimized. Under the optimum conditions, linearity of the method was observed in the range of 0.0500–100 μg L^?1 for TCS, 0.0250–50.0 μg L^?1 for TCC, and 0.500–100 μg L^?1 for M-TCS, respectively, with correlation coefficients (r²) > 0.9945. The limits of detection (LODs) ranged from 45.1 to 236 ng L^?1. TCS in domestic waters was detected with the concentration of 2.08 μg L^?1. The spiked recoveries of three target compounds in river water, irrigating water, reclaimed water and domestic water samples were achieved in the range of 96.4–121%, 64.3–84.9%, 77.2–115% and 75.5–106%, respectively. As a result, this method can be successfully applied for the rapid and convenient determination of TCS, TCC and M-TCS in real water samples.     

Ultra-preconcentration and determination of thirteen organophosphorus pesticides in water samples using solid-phase extraction followed by dispersive liquid–liquid microextraction and gas chromatography with flame photometric detection

An ultra-preconcentration technique composed of solid-phase extraction (SPE) and dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography–flame photometric detection (GC–FPD) was used for determination of thirteen organophosphorus pesticides (OPPs) including phorate, diazinon, disolfotane, methyl parathion, sumithion, chlorpyrifos, malathion, fenthion, profenphose, ethion, phosalone, azinphose-methyl and co-ral in aqueous samples. The analytes were collected from large volumes of aqueous solutions (100 mL) into 100 mg of a SPE C₁₈ sorbent. The effective variables of SPE including type and volume of elution solvent, volume and flow rate of sample solution, and salt concentration were investigated and optimized. Acetone was selected as eluent in SPE and disperser solvent in DLLME and chlorobenzene was used as extraction solvent. Under the optimal conditions, the enrichment factors were between 15,160 and 21,000 and extraction recoveries were 75.8–105.0%. The linear range was 1–10,000 ng L^?1 and limits of detection (LODs) were between 0.2 and 1.5 ng L^?1. The relative standard deviations (RSDs) for 50 ng L^?1 of OPPs in water with and without an internal standard, were in the range of 1.4–7.9% (n = 5) and 4.0–11.6%, respectively. The relative recoveries of OPPs from well and farm water sat spiking levels of 25 and 250 ng L^?1 were 88–109%.     

Using enantioselective dispersive liquid–liquid microextraction for the microseparation of trans-cyclohexane-1,2-diamine enantiomers

A new chiral separation system effective for the enantioselective extraction of racemic trans-cyclohexane-1,2-diamine is presented. Enantioselective dispersive liquid–liquid microextraction has been used for the chiral microseparation of trans-cyclohexane-1,2-diamine, with a chiral azophenolic crown ether being identified as a versatile chiral selector. The influence of various process conditions on the extraction performance was studied experimentally. It was found that the operational selectivity in one extraction step is mainly related to the type and volume of the solvents, chiral selector concentration, extraction time, temperature of sample solution, and pH. At optimum conditions (300 μL of diethyl ether as the extraction solvent 1 mL of methanol as the disperser solvent, with 5 mmol L^?1 chiral selector concentration, pH of the sample equal to 4.5, 30 min extraction time and a temperature of 10 °C), the distribution ratio of (R,R)- and (S,S)-trans-cyclohexane-1,2-diamine was 18.3 and 1.8, respectively, while the enantioselectivity value of 10.2 was found at the optimum condition.     

Analysis of volatile compounds in Herba Asari by single-drop micro-extraction gas chromatography mass spectrometry

A rapid headspace single-drop micro-extraction(mix) gas chromatography mass spectrometry(SDMEGC -MS) for the analysis of the volatile compounds in Herba Asari was developed in this study.A mixed solvent of n-tridecane and butyl acetate(1:1) was finally used for the extraction at 70 C for 15 min with sample amount of 0.750 g and 100 mesh particle size.Under the determined conditions,the pound samples of Herba Asari were directly applied for the analysis.SDME-GC-MS,SPME-GC-MS and SD-GCMS methods were compared and the results showed that SDME-GC-MS method was a simple, inexpensive and effective way to measure the volatile compounds in Herba Asari and could be used for the analysis of volatile compounds in complex samples.     

Enthalpies of mixing of liquid systems for lead free soldering: Al-Cu-Sn system

The present work refers to high-temperature drop calorimetric measurements on liquid Al–Cu, Al–Sn, and Al–Cu–Sn alloys. The binary systems have been investigated at 973 K, up to 40 at.% Cu in case of Al–Cu, and over the entire concentrational range in case of Al–Sn. Measurements in the ternary Al–Cu–Sn system were performed along the following cross-sections: x_Al/x_Cu = 1:1, x_Al/x_Sn = 1:1, x_Cu/x_Sn = 7:3, x_Cu/x_Sn = 1:1, and x_Cu/x_Sn = 3:7 at 1273 K. Experimental data were used to find ternary interaction parameters by applying the Redlich–Kister–Muggianu model for substitutional solutions, and a full set of parameters describing the concentration dependence of the enthalpy of mixing was derived. From these, the isoenthalpy curves were constructed for 1273 K. The ternary system shows an exothermic enthalpy minimum of approx. ?18,000 J/mol in the Al–Cu binary and a maximum of approx. 4000 J/mol in the Al–Sn binary system. The Al–Cu–Sn system is characterized by considerable repulsive ternary interactions as shown by the positive ternary interaction parameters.     

Development of a new dispersive liquid–liquid microextraction method in a narrow-bore tube for preconcentration of triazole pesticides from aqueous samples

In the present work a new, simple, rapid and environmentally friendly dispersive liquid–liquid microextraction (DLLME) method has been developed for extraction/preconcentration of some triazole pesticides in aqueous samples and in grape juice. The extract was analyzed with gas chromatography–flame ionization detection (GC–FID) or gas chromatography–mass spectrometry (GC–MS). The DLLME method was performed in a narrow-bore tube containing aqueous sample. Acetonitrile and a mixture of n-hexanol and n-hexane (75:25, v/v) were used as disperser and extraction solvents, respectively. The effect of several factors that influence performance of the method, including the chemical nature and volume of the disperser and extraction solvents, number of extraction, pH and salt addition, were investigated and optimized. Figures of merit such as linearity (r² > 0.995), enrichment factors (EFs) (263–380), limits of detection (0.3–5 μg L^?1) and quantification (0.9–16.7 μg L^?1), and relative standard deviations (3.2–5%) of the proposed method were satisfactory for determination of the model analytes. The method was successfully applied for determination of target pesticides in grape juice and good recoveries (74–99%) were achieved for spiked samples. As compared with the conventional DLLME, the proposed DLLME method showed higher EFs and less environmental hazards with no need for centrifuging.     

Determination of atorvastatin in human serum by salting out assisted solvent extraction and reversed-phase high-performance liquid chromatography–UV detection

A simple and rapid technique based on salting out assisted solvent extraction was developed for extraction of atorvastatin from serum sample and high performance liquid chromatography–UV was used for its detection. In the present study, 1.0 mL serum was extracted by 0.5 mL of acetonitrile and some parameters that can affect extraction such as type and volume of extraction solvent, type of salt, and pH were optimized. Under optimized experimental conditions, the calibration curve was found to be linear in the range of 0.001–10 ng mL⁻¹ in human serum and the correlation coefficient (R²) and the limits of detection were >0.99 and 0.0005 ng mL⁻¹, respectively. The accuracy of the method in terms of average recovery of the compound in spiked serum and water samples was better than 90%.     

Isobaric vapor–liquid phase equilibria for the binary systems of tert-butanol + 2-ethyl-1-hexanol and n-butanol + 2-ethyl-1-hexanol

Isobaric vapor–liquid equilibria for the binary mixtures of tert-butanol (TBA) + 2-ethyl-1-hexanol and n-butanol (NBA) + 2-ethyl-1-hexanol were experimentally investigated at atmospheric pressure in the temperature range of 353.2–458.2 K. The raw experimental data were correlated using the UNIQUAC and NRTL models and used to estimate the interaction parameters between each pair of components in the systems. The experimental activity coefficients were obtained using the gas chromatographic method and compared with the calculated data obtained from these equilibrium models. The results show that UNIQUAC model gives better correlation than NRTL for these binary systems. The liquid–liquid extraction of TBA from aqueous solution using 2-ethyl-1-hexanol was demonstrated by simulation and the variation of separation factor of TBA at several temperatures was reported.     

Voltammetric studies on the interaction of amikacin with methyl blue and its analytical application

A new method to determine the concentration of amikacin(AMK)using methyl blue(MB)as electrochemical probe was developed in this paper.In pH 4.5 Britton-Robinson(B-R)buffer solution,the MB reacted with AMK to form ion association complexes,which led to the reductive peak current of MB at-0.275 V(versus SCE)to decrease,and the decreases were linear with the concentration of AMK in the range of 1.0-60.0 mg/L,the regression of equation isΔIp(nA)=-8.48 102.36c(mg/L), correlation coefficientγis 0.997.The conditions for determining the concentration of AMK using linear sweep voltammetry(SLV) were optimized.The method was used to determine the content of amikacin commercially available with satisfactory results.     

Toward use of a nano layered double hydroxide/ammonium pyrrolidine dithiocarbamate in speciation analysis: One-step dispersive solid-phase extraction of chromium species in human biological samples

Chromium is a controversial element with an important essentiality and toxicity. Depending on its different species, its speciation analysis in bio-origin matrices is of utmost importance. Ammonium pyrrolidine dithiocarbamate (APDC) and layered double hydroxide (LDH) nanoparticles, with the purpose of combining their outstanding performances, were served to speciate chromium ions in human biological samples. The as-obtained sorbent (nano LDH-APDC) - after characterization by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM) - was used as a novel pH-sensitive adsorbent in an integrated one-step dispersive solid-phase extraction (I-OS-DSPE), which combines the benefits of the air-assisted microextraction and dispersive solid-phase extraction methods. An interesting feature of the nano LDH-APDC sorbent is that it is dissolved in an aqueous solution when the pH of the solution is lower than 4. Thus the analyte elution step, as required in most of the sorbent-based extraction methods, was obviated by dissolving the sorbent in an acidic solution after extraction and separation from the sample solution. The Cr(VI) ions were first extracted, while the Cr(III) ions remained in the aqueous solution. The extract was then directly injected into a flame atomic absorption spectrometer with a micro-sampling introduction system, and the concentration of the Cr(III) ions was calculated by its subtraction from the total chromium ions present. Several variables including the pH (5), type and amount of the nanosorbent used (30 mg of nano (Zn-Al) LDH-APDC), number of extraction cycles (15 times), and elution conditions (200 µL of 6.0 mol L⁻¹ HNO₃) were investigated to achieve the maximum extraction efficiency. Under the optimum experimental conditions, the limit of detection, linear range, consumptive index, and enrichment factor for the Cr(VI) ions were 2.4 μg L⁻¹, 8.0–640 μg L⁻¹, 0.24, and 42.5 ± 1, respectively. These findings suggested that nano (Zn-Al) LDH-APDC could be regarded as a promising adsorbent for an efficient speciation of the chromium species in the human hair, nail, saliva, plasma, and urine samples.     

High pressure phase equilibria in the system 1,1,1,2-tetrafluoroethane + heptylbenzene

Vapour–liquid, liquid–liquid and liquid–liquid–vapour equilibria for the system 1,1,1,2-tetrafluoroethane + heptylbenzene were determined in the temperature range from 260 to 400 K and at pressures up to 12 MPa. The system was found to be a type II system according to the classification of Van Konynenburg and Scott. The (l₂=l₁)g critical endpoint was found at T=320.07 K and P=1.155 MPa. The mole fraction of heptylbenzene in the critical liquid phase in the critical endpoint is approximately 0.20.     

Phase equilibrium data for the ternary system (propane + chloroform + oryzanol)

The compound oryzanol available in the rice bran (oriza sativa) is well known for its antioxidant activity. Phase equilibrium data involving oryzanol in compressed fluids, hardly found in the literature, are important to provide the basis for the extraction and fractionation processes. In this sense, the aim of this work is to report phase equilibrium measurements for the system (γ-oryzanol + chloroform) in compressed propane. Phase equilibrium experiments were performed using the static synthetic method (cloud points transition data) in a high-pressure variable-volume view cell in the temperature range of 303 K to 353 K, pressures up to 17 MPa, for oryzanol overall mass fractions of 2 wt%, 5 wt% and 10 wt% in (propane + chloroform) mixtures. A complex phase behaviour comprising vapour–liquid, liquid–liquid, vapour–liquid–liquid, solid–liquid, solid–liquid–liquid, solid–liquid–liquid–vapour transitions were visually observed for the system studied.     

Preface

The anisotropic rototranslational scattering spectra of nitrogen gas at high frequency up to 700 cm⁻¹ for several temperatures and from low densities are analyzed in terms of new site–site (M3SV) intermolecular potential and interaction-induced pair polarizability models, using quantum spectral shapes computations. Our theoretical calculations take into account multipole contributions from the mean value and anisotropy of the dipole–dipole polarizability tensor α, two independent components of the dipole–octopole polarizability tensor E and dipole–dipole–quadrupole hyperpolarizability tensor B. The high-frequency wings are discussed in terms of the collision-induced rotational Rayleigh effect and estimates for the dipole–octopole polarizability |E₄| are obtained and checked with recent ab initio theoretical value. Good comparison is found in the frequency range 0–400 cm⁻¹ between the theoretical and experimental spectra. When an exponential contribution [exp(−ν/ν₀)] with ν₀ = 425 cm⁻¹ is considered to model very short-range light scattering mechanisms at room temperature, good agreement is found over the whole frequency range.     

Determination of erythromycins in fermentation broth using liquid phase extraction with back extraction combined with high performance liquid chromatography

Liquid phase extraction with back extraction (LPE-BE) combined with high performance liquid chromatography-diode array detection (HPLC-DAD) was applied for the extraction and determination of erythromycin A, B and C in fermentation broths. According to this procedure, the fermentation broth with the adjustment pH at a fixed value of 10 was first mixed with organic solvent (V_broth/V_org = 1.0). After shaking, the mixture was separated into two phases by microfuging at 13,000 rpm for 15 min. Then back extraction was performed into the acidic aqueous phase with pH 5.0 (V_org/V_aq = 1.0). After centrifugation at 3000, the two phases were separated and 50 μL of the acidic aqueous phase was injected into the HPLC. The effects of different variables such as the nature of extraction solvent and the pH of samples and buffer were investigated. At the most appropriate conditions, dynamic linear ranges of 0.5–8, 0.1–0.9 and 0.1–0.9 mg mL⁻¹ and limits of detection of 0.03, 0.003 and 0.002 mg mL⁻¹ were obtained for erythromycin A, B and C, respectively. Relative standard deviations (RSDs) of the proposed method were less than 9.5%. The mean recoveries were 99.5%. The proposed method is simple and sensitive with highly clean-up effect and it can be used for monitoring the progress of erythromycin fermentation.     

A multiresidue method for the determination 234 pesticides in Korean herbs using gas chromatography mass spectrometry

A rapid, specific and sensitive multiresidue method based on dispersive solid phase extraction sample preparation and gas chromatography with the mass spectrometric detection for the analysis of 234 pesticides in Korean herbs (Acanthopanax senticosus, Morus alba L., Hovenia dulcis) has been developed. Method recoveries were found to be between 62 and 119% with relative standard deviation lower than 21% for all compounds in the concentration range of 0.05 to 0.400 mg kg^? 1. Limits of quantification of most compounds are below 0.050 mg kg^? 1. The data demonstrate that this method was successfully used for analysis of 234 pesticides in Korean herbs.     

Determination of resveratrol in red wine by solid phase extraction-flow injection chemiluminescence method

A sensitive flow injection chemiluminescence method has been developed for the detection of resveratrol in red wine based on the fact that resveratrol can greatly enhance chemiluminescence reaction between KMnO_4 and HCHO in sulfuric acid medium. Analytes were pre-concentrated on solid sorbents (C_(18) solid-phase extraction cartridges).Under the optimum conditions,the proposed method allows the measurement of resveratrol over the range of 1.32×10~(-8) to 1.32×10~(-5) mol/L with a detection limit of 3.30×10~(-9) mol/L,and the relative standard deviation for 1.32×10~(-5) mol/L resveratrol (n=11) is 3.8%.This method has been successfully applied for the determination of the resveratrol in red wine.Furthermore,the possible reaction mechanism was also discussed.     

In vitro metabolic study of Rhizoma coptidis extract using liver microsomes immobilized on magnetic nanoparticles

Although metabolic study of individual active compounds isolated from herbal plants has been intensive, it cannot truly reflect the fate of herbs because the herbal extracts in use have many constituents. To address this problem, whole extracts of herbs should be investigated. Microsomes have been heavily used in the in vitro metabolic study of drugs, and various materials have been used to immobilize microsomes to develop highly effective and reusable bioreactors in this field. In this work, rat liver microsomes were immobilized on magnetic nanoparticles (LMMNPs) to develop a highly active and recoverable nanoparticle bioreactor. Using this bioreactor, we investigated the in vitro metabolism of Rhizoma coptidis extract. Incubation of berberine, a major active ingredient of R. coptidis, with LMMNPs for 20 min produced two metabolites, i.e., demethyleneberberine and thalifendine, at high levels. From a comparison of the time courses of thalifendine formation obtained by ultraperformance liquid chromatography–mass spectrometry analysis, it was found that LMMNPs had a higher biological activity than free liver microsomes in metabolizing berberine. Further, the activity of LMMNPs remained almost unchanged after six consecutive uses in the incubation tests. Metabolism of R. coptidis extracts by LMMNPs was studied. The same two metabolites of berberine, i.e., demethyleneberberine and thalifendine, were detected. After a thorough study seeking support for this observation, it was found that demethyleneberberine was the common metabolite of five protoberberine-type alkaloids present in R. coptidis extract, including palmatine, jatrorrhizine, columbanine, epiberberine, and berberine.

Low power capacitively coupled plasma microtorch for simultaneous multielemental determination by atomic emission using microspectrometers

A new, low power capacitively coupled plasma microtorch (30 W, 13.56 MHz, 0.5 L min^?1 Ar) was investigated in conjunction with commercially available microspectrometers for the simultaneous multielemental analysis by atomic emission spectrometry of liquid samples without desolvation. Emission spectrum is simpler than in ICP-AES, the resonance lines are the most intense, so that a microspectrometer with FWHM of at least 1.5 nm is satisfactory for the record. The deviation from the Boltzmann distribution for Fe I has demonstrated the departure from the LTE in plasma. The non-spectral matrix effects of Li, Na, K, Ca and Mg on analytes emission are depressive and depend on matrix volatility, ionization potential of the interferent and analyte excitation energy. The detection limits (μg mL^?1) are in the range 0.003 (Li) and 1.5 (Mn). The use of the standard additions method allowed the simultaneous determination of elements in environmental certified reference materials with overall recovery of 95 ± 10% and relative standard deviation of 1.7–8.2%. Compared to the traditional ICP, the microtorch has a simple construction, runs at low argon flow and can be integrated in a portable system suitable for in-situ simultaneous determination of elements.     

Liquid extraction of polyhydric alcohols from water using [A336][SCN] as a solvent

This work demonstrated the possibility of hydrophobic ionic liquid tricaprylmethylammonium thiocyanate ([A336][SCN]) as a solvent in the separation by extraction of polyhydric alcohols from their mixtures with water. The knowledge of (liquid + liquid) equilibrium (LLE) of these mixtures is essential for the design of the extraction process. For this reason, the LLE data of the ternary systems {[A336][SCN] + water + glycerol, or ethylene glycol, or 1,2-propanediol, or 1,3-propanediol} were determined at T = 303.2 K and atmospheric pressure. The reliability of the tie-lines data was ascertained by applying the Othmer–Tobias equation, and the non-random two liquid (NRTL) model used to fit the experimental LLE data. The effectiveness of the extraction of polyhydric alcohols from water was evaluated using the solute distribution ratio and the selectivity. The extraction capability of [A336][SCN] was compared with that of other ILs. The results indicated that the [A336][SCN] was suitable for use as a solvent in (liquid + liquid) extraction of polyhydric alcohols from water.     

Hollow fiber supported liquid membrane microextraction of Cu2+ followed by flame atomic absorption spectroscopy determination

Hollow fiber supported liquid membrane microextraction, a relatively new sample preparation technique, has attracted much interest in the field of environmental analysis. In the current study, a novel method based on hollow-fiber liquid-phase microextraction and flame atomic absorption spectrometry (FAAS) for the measurement of copper ion in aqueous samples is described. Hollow-fiber liquid-phase microextraction conditions such as the type of extraction solvent, pH, the stirring rate, and the amounts of chelating agents, sample volume, and the extraction time were investigated. Under the optimized conditions, the linear range was found to be 0.01–15 μg ml^?1 for copper ion, and the limit of detection to be 0.004 μg ml^?1. Tap water and surface water samples collected from Mashhad, Iran and Dorongar river; Khorasan, Iran, respectively, were successfully analyzed using the proposed method. The recoveries from the spiked water samples were 72.4% and 105%, respectively; and the relative standard deviation (RSD) at the 2 μg ml^?1 level was 6%.