Determination of some sulfonylurea herbicides in soil by a novel liquid-phase microextraction combined with sweeping micellar electrokinetic chromatography

A novel method for the determination of five sulfonylurea herbicides in soil was developed by a dispersive solid-phase extraction (DSPE) clean-up followed by dispersive liquid–liquid microextraction (DLLME), prior to sweeping micellar electrokinetic chromatography (MEKC). In the DSPE-DLLME, 10 g of soil sample was first extracted with 10 mL of acetonitrile containing 5% formic acid (pH 3.0). The extract was then cleaned-up by a DSPE with C₁₈ as sorbent. A 1 mL aliquot of the resulting extract was then added into a centrifuge tube containing 5 mL of water adjusted to pH 2.0 and 60.0 μL chlorobenzene (as extraction solvent) for DLLME procedure. Then, the organic sample extraction solution was evaporated to dryness, and reconstituted with 20.0 μL of 1.0 mmol L⁻¹ Na₂HPO₄ (pH 10.0) for sweeping-MEKC analysis after DLLME. Under optimized conditions, the method provided as high as 3,000- to 5,000-fold enrichments factors. The linearity of the method was in the range of 3.3–200 ng g⁻¹ for chlorimuron ethyl and bensulfuron methyl, and in the range of 1.7–200 ng g⁻¹ for tribenuron methyl, chlorsulfuron and metsulfuron methyl, with the correlation coefficients (r) ranging from 0.9965 to 0.9983, respectively. The limits of detection (LODs) ranged from 0.5 to 1.0 ng g⁻¹. The intraday relative standard deviations (RSDs, n = 5) were below 5.3% and interday RSDs (n = 15) within 6.8%. The recoveries of the method for the five sulfonylureas from soil samples at spiking levels of 5.0, 20.0, and 100.0 ng g⁻¹ were 76.0–93.5%, respectively. The developed method has been successfully applied to the analysis of the target sulfonylurea herbicide residues in soil samples with a satisfactory result.     

A confirmatory method for the determination of phenolic endocrine disruptors in honey using restricted-access material–liquid chromatography–tandem mass spectrometry

The present work describes the development and validation of an analytical method based on liquid chromatography (LC), coupled with tandem mass spectrometry (MS/MS) that allows the determination and confirmation of several endocrine-disrupting chemicals (EDCs) in honey. The EDCs studied were nine phenols of different nature: chlorophenols (2,4-dichlorophenol, 2,4,5-trichlorophenol, and pentachlorophenol), alkylphenols (4-tert-butylphenol, 4-tert-octylphenol, and 4-n-octylphenol) bisphenols (bisphenol-A and bisphenol-F), and 4-tert-butylbenzoic acid. The method incorporates a restricted-access material (RAM), coupled on-line to the LC-MS/MS system, which allows direct injection of the matrix into the RAM-LC-MS/MS system. The optimized method developed, RAM-LC-MS/MS, was applied to fortified honey samples, affording detection limits in the 0.6–7.2 ng g⁻¹ range, calculated for a signal-to-noise ratio of 3. In addition, the method was validated as a quantitative confirmatory method according to European Union Decision 2002/657/EC. The validation criteria evaluated were linearity, repeatability, reproducibility, recovery, decision limits, detection capabilities, specificity, and ruggedness. Repeatability and within-laboratory reproducibility were evaluated at two concentration levels, being ±11% or below at 20 ng g⁻¹. The decision limits (CC_α) and detection capabilities (CC_β) were in the 1.7–12.6 and 2.8–21.6 ng g⁻¹ range, respectively.     

Determination of pharmaceuticals,steroid hormones,and endocrine-disrupting personal care products in sewage sludge by ultra-high-performance liquid chromatography–tandem mass spectrometry

A sensitive method has been developed and validated for the determination of diverse groups of pharmaceuticals, steroid hormones, and hormone-like personal care products in sewage sludge. Samples were extracted by ultrasonic-assisted extraction followed by solid-phase extraction cleanup. For determination of estrogens and hormone-like phenolic compounds, sample extracts were further derivatized with dansyl chloride and purified with silica gel column chromatography to improve the analytical sensitivity. The chemicals were determined by ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS) in multiple-reaction monitoring mode. Recoveries ranged mostly from 63% to 119% with relative standard deviations within 15%. Method quantification limits were 0.1–3 ng g⁻¹ dry weight (dw) for sewage sludge. The method was applied to a preliminary investigation of pharmaceuticals and personal care products (PPCPs) in sewage sludge and sediment in the Pearl River Delta, South China. Triclosan, triclocarban, 2-phenylphenol, bisphenol A, and parabens were ubiquitously detected at 3.6–5088.2 ng g⁻¹ dw in sludge and 0.29–113.1 ng g⁻¹ dw in sediment samples, respectively. Estrone, carbamazepine, metoprolol, and propranolol were also frequently quantified in the sludge and sediment samples. The dewatering process caused no significant losses of these PPCPs in sewage sludge.     

Fast screening immunoassay of sulfonamides in commercial fish samples

An indirect competitive enzyme-linked immunosorbent assay (ELISA) was developed in plate to detect three sulfonamide residues (sulfamerazine (SMR), sulfadimetoxine (SDM), and sulfadiazine (SDZ)) in gilthead sea bream (Sparus aurata) samples. Different extraction methodologies—using methanol/water 1:1 (v/v) + ethylene diamine tetraacetic acid (EDTA) 0.5% (m/v), acetonitrile, phosphate-buffered saline (PBS) 10 mmol L⁻¹ pH 7 and acetate buffer 100 mmol L⁻¹ pH 5—and cleanup steps, based on solid-phase extraction (C₁₈, SCX, Si) or liquid extraction with hexane, were assayed. As optimum, a fast and simple method using acetonitrile was selected to extract the sulfonamide residues from the edible muscle of fish. Due to matrix effects, a standard addition calibration curve in fish extract is necessary for quantification purposes. Sulfonamide-free samples were spiked at different concentration levels (between 30 and 90 ng g⁻¹, 5–15 ng mL⁻¹ in plate) and average recoveries (n = 8), ranging from 71% to 95%, 65% to 79%, and 72% to 95%, were obtained for SMR, SDM, and SDZ, respectively. The assay detection limits for these antibiotics were lower than 100 μg kg⁻¹ (maximum residue level established by the European Union). The accuracy was evaluated by spiking blank fish extracts at different concentrations (10–40 ng mL⁻¹, 5–20 ng mL⁻¹ in plate), and the relative errors ranged between ±20%. Finally, in order to confirm the utility of the developed ELISA as a screening methodology, fish samples from different supermarkets were analyzed, and results were compared with those obtained by a validated high-performance liquid chromatography (HPLC) method. The correlation between the results obtained by both ELISA and HPLC methods is satisfactory.      

Determination of melamine in animal feed based on liquid chromatography tandem mass spectrometry analysis and dynamic microwave-assisted extraction coupled on-line with strong cation-exchange resin clean-up

In this work, a new method was developed for the determination of melamine (MEL) in animal feed. The method was based on the on-line coupling of dynamic microwave-assisted extraction (DMAE) to strong cation-exchange (SCX) resin clean-up. The MEL was first extracted by 90% acidified methanol aqueous solution (v/v, pH = 3) under the action of microwave energy, and then the extract was cooled and passed through the SCX resin. Thus, the protonated MEL was retained on the resin through ion exchange interaction and the sample matrixes were washed out. Some obvious benefits were achieved, such as acceleration of analytical process, together with reduction in manual handling, risk of contamination, loss of analyte, and sample consumption. Finally, the analyte was separated by a liquid chromatograph with a SCX analytical column, and then identified and quantitatived by a tandem mass spectrometry with positive ionization mode and multiple-reaction monitoring. The DMAE parameters were optimized by the Box–Behnken design. The linearity of quantification obtained by analyzing matrix-matched standards is in the range of 50–5,000 ng g⁻¹. The limit of detection and limit of quantification obtained are 12.3 and 41.0 ng g⁻¹, respectively. The mean intra- and inter-day precisions expressed as relative standard deviations with three fortified levels (50, 250, and 500 ng g⁻¹) are 5.1% and 7.3%, respectively, and the recoveries of MEL are in the range of 76.1–93.5%. The proposed method was successfully applied to determine MEL in different animal feeds obtained from the local market. MEL was detectable with the contents of 279, 136, and 742 ng g⁻¹ in three samples.      

Dispersive liquid–liquid microextraction coupled to liquid chromatography for thiamine determination in foods

A miniaturized dispersive liquid–liquid microextraction (DLLME) procedure coupled to liquid chromatography (LC) with fluorimetric detection was evaluated for the preconcentration and determination of thiamine (vitamin B₁). Derivatization was carried out by chemical oxidation of thiamine with 5 × 10⁻⁵ M ferricyanide at pH 13 to form fluorescent thiochrome. For DLLME, 0.5 mL of acetonitrile (dispersing solvent) containing 90 μL of tetrachloroethane (extraction solvent) was rapidly injected into 10 mL of sample solution containing the derivatized thiochrome and 24% (w/v) sodium chloride, thereby forming a cloudy solution. Phase separation was carried out by centrifugation, and a volume of 20 μL of the sedimented phase was submitted to LC. The mobile phase was a mixture of a 90% (v/v) 10 mM KH₂PO₄ (pH 7) solution and 10% (v/v) acetonitrile at 1 mL min⁻¹. An amide-based stationary phase involving a ligand with amide groups and the endcapping of trimethylsilyl was used. Specificity, linearity, precision, recovery, and sensitivity were satisfactory. Calibration graph was carried out by the standard additions method and was linear between 1 and 10 ng mL⁻¹. The detection limit was 0.09 ng mL⁻¹. The selectivity of the method was judged from the absence of interfering peaks at the thiamine elution time for blank chromatograms of unspiked samples. A relative standard deviation of 3.2% was obtained for a standard solution containing thiamine at 5 ng mL⁻¹. The esters thiamine monophosphate and thiamine pyrophosphate can also be determined by submitting the sample to successive acid and enzymatic treatments. The method was applied to the determination of thiamine in different foods such as beer, brewer’s yeast, honey, and baby foods including infant formulas, fermented milk, cereals, and purees. For the analysis of solid samples, a previous extraction step was applied based on an acid hydrolysis with trichloroacetic acid. The reliability of the procedure was checked by analyzing a certified reference material, pig’s liver (CRM 487). The value obtained was 8.76 ± 0.2 μg g⁻¹ thiamine, which is in excellent agreement with the certified value, 8.6 ± 1.1 μg g⁻¹.     

Simultaneous determination of albendazole and its metabolites in fish muscle tissue by stable isotope dilution ultra-performance liquid chromatography tandem mass spectrometry

A rapid, specific, and sensitive method utilizing ultra-performance liquid chromatography tandem mass spectrometry was developed and validated to determine albendazole, albendazole sulfoxide, albendazole sulfone, and albendazole 2-aminosulfone in fish muscle tissue. The fish samples were extracted with ethyl acetate, then the organic phase was evaporated to dryness, and the residue was reconstituted in methanol–water solution and cleaned up by n-hexane. Reversed-phase separation of target compounds was achieved using a BEH C18 column and a gradient consisting of 0.2% (v/v) formic acid and methanol. Tandem mass spectrometry analyses were performed on a triple–quadrupole tandem mass spectrometer. In the whole procedure, the isotope-labeled internal standards were used to correct the matrix effect and variations associated with the analysis. The method was validated with respect to linearity, specificity, accuracy, and precision. The method exhibited a linear response from 0.1 to 20 ng mL^-1 (r ² > 0.9985). The limit of quantitation for albendazole (ABZ), albendazole sulfoxide (ABZSO), albendazole sulfone (ABZSO₂), and albendazole 2-aminosulfone (ABZ-2-NH₂SO₂) was 0.1, 0.1, 0.1, and 0.2 ng g^-1, respectively. The mean recoveries of ABZ, ABZSO, ABZSO₂, and ABZ-2-NH₂SO₂ spiked at a level of 0.2–5.0 ng g^-1 were 95.3–113.7%, and the relative standard deviations of intra- and inter-day measurements were less than 6.38%. The method was later successfully applied to the determination of albendazole and its three metabolites in 60 fish samples collected from local markets.     

Determination of total Sb,Se, Te,and Bi and evaluation of their inorganic species in garlic by hydride-generation–atomic-fluorescence spectrometry

A sensitive and simple analytical method has been developed for determination of Sb(III), Sb(V), Se(IV), Se(VI), Te(IV), Te(VI), and Bi(III) in garlic samples by using hydride-generation–atomic-fluorescence spectrometry (HG–AFS). The method is based on a single extraction of the inorganic species by sonication at room temperature with 1 mol L⁻¹ H₂SO₄ and washing of the solid phase with 0.1% (w/v) EDTA, followed by measurement of the corresponding hydrides generated under two different experimental conditions directly and after a pre-reduction step. The limit of detection of the method was 0.7 ng g⁻¹ for Sb(III), 1.0 ng g⁻¹ for Sb(V), 1.3 ng g⁻¹ for Se(IV), 1.0 ng g⁻¹ for Se(VI), 1.1 ng g⁻¹ for Te(IV), 0.5 ng g⁻¹ for Te(VI), and 0.9 ng g⁻¹ for Bi(III), in all cases expressed in terms of sample dry weight.     

Anabolic, doping, and lifestyle drugs, and selected metabolites in wastewater—detection, quantification, and behaviour monitored by high-resolution MS and MS n before and after sewage treatment

Municipal wastewater has been examined for steroids, β₂-agonists, stimulants, diuretics, and phosphodiesterase type V inhibitors (PDE type V inhibitors), which are “dual-use-drugs” applied either as anabolic, doping, and lifestyle drugs or for treatment of diverse diseases. To identify their origin, fitness centre discharges under suspicion of being point sources and sewage-treatment plant feed and effluents were sampled and concentrations determined. Sensitive and selective methods for determination and quantification based on solid-phase extraction (SPE) followed by high-performance liquid chromatography–high resolution mass and tandem mass spectrometry (HPLC–(HR)MS and HPLC–MS–MS) were developed and established for analysis of these compounds in wastewater and to assess their effect on the environment. The methods developed enabled quantification at trace concentrations (limit of quantification (LOQ): 5 ng L⁻¹). Of the steroids and stimulants under investigation, testosterone, methyltestosterone, and boldenone or ephedrine, amphetamine, and MDMA (3,4-methylendioxy-N-methylamphetamine) were observed at up to 5 μg L⁻¹ (ephedrine). Of the β₂-agonists salbutamol only, and of the diuretics furosemide and hydrochlorothiazide were confirmed in the extracts. Quite high concentrations of the PDE type V inhibitors sildenafil, tadalafil, and vardenafil and their metabolites were confirmed in fitness centre discharges (sildenafil: 1,945 ng L⁻¹) whereas their concentrations in municipal wastewater did not exceed 35 ng L⁻¹. This study identified anabolic and doping drugs in wastewater for the first time. Results obtained from wastewater treatment plant effluents proved that these “dual-use-drugs”, with the exception of hydrochlorothiazide, were mostly eliminated.     

Organosilica composite for preconcentration of phenolic compounds from aqueous solutions

A new adsorbent is proposed for the solid-phase extraction of phenol and 1-naphthol from polluted water. The adsorbent (TX-SiO₂) is an organosilica composite made from a bifunctional immobilized layer comprising a major fraction (91%) of hydrophilic diol groups and minor fraction (9%) of the amphiphilic long-chain nonionic surfactant Triton X-100 (polyoxyethylated isooctylphenol) (TX). Under static conditions phenol was quantitatively extracted onto TX-SiO₂ in the form of a 4-nitrophenylazophenolate ion associate with cetyltrimethylammonium bromide. The capacity of TX-SiO₂ for phenol is 2.4 mg g⁻¹ with distribution coefficients up to 3.4 × 10⁴ mL g⁻¹; corresponding data for 1-naphthol are 1.5 mg g⁻¹ and 3 × 10³ mL g⁻¹. The distribution coefficient does not change significantly for solution volumes of 0.025–0.5 L and adsorbent mass less than 0.03 g; 1–90 μg analyte can be easily eluted by 1–3 mL acetonitrile with an overall recovery of 98.2% and 78.3% for phenol and 1-naphthol, respectively. Linear correlation between acetonitrile solution absorbance (A ₅₄₀) and phenol concentration (C) in water was found according to the equation A ₅₄₀ = (6 ± 1) × 10⁻² + (0.9 ± 0.1)C (μmol L⁻¹) with a detection range from 1 × 10⁻⁸ mol L⁻¹ (0.9 μL g⁻¹) to 2 × 10⁻⁷ mol L⁻¹ (19 μL g⁻¹), a limit of quantification of 1 μL g⁻¹ (preconcentration factor 125), correlation coefficient of 0.936, and relative standard deviation of 2.5%. A solid-phase colorimetric method was developed for quantitative determination of 1-naphthol on adsorbent phase using scanner technology and RGB numerical analysis. The detection limit of 1-naphthol with this method is 6 μL g⁻¹ while the quantification limit is 20 μL g⁻¹. A test system was developed for naked eye monitoring of 1-naphthol impurities in water. The proposed test kit allows one to observe changes in the adsorbent color when 1-naphthol concentration in water is 0.08–3.2 mL g⁻¹.     

A sensitive liquid chromatographic-mass spectrometric method for simultaneous determination of dehydroevodiamine and limonin from Evodia rutaecarpa in rat plasma

A liquid chromatographic–mass spectrometric (LC–MS) method has been developed and validated for simultaneous determination of dehydroevodiamine and limonin from Evodia rutaecarpa in rat plasma. After addition of the internal standard, domperidone, plasma samples were extracted by liquid–liquid extraction with ethyl acetate and separated on an Apollo C₁₈ column (250 mm × 4.6 mm, 5 μm), with methanol–0.01% formic acid water (60:40, v/v) as mobile phase, within a runtime of 12.0 min. The analytes were detected without interference in the selected ion monitoring (SIM) mode with positive electrospray ionization. The linear range was 1.0–500 ng mL⁻¹ for dehydroevodiamine and 2.0–1,000 ng mL⁻¹ for limonin, with lower limits of quantitation of 1.0 and 2.0 ng mL⁻¹, respectively. Intra-day and inter-day precision were within 6.0% and 10.9%, respectively, for both analytes, and the accuracy (relative error, RE, %) was less than 4.8% and 6.5%, respectively. The validated method was successfully applied to a comparative pharmacokinetic study of dehydroevodiamine and limonin in rat plasma after oral administration of dehydroevodiamine, limonin, and an aqueous extract of Evodiae fructus. The results indicated there were obvious differences between the pharmacokinetic behavior after oral administration of an aqueous extract of Evodiae fructus compared with single substances.     

In-sample acetylation-non-porous membrane-assisted liquid–liquid extraction for the determination of parabens and triclosan in water samples

A procedure for the determination of seven parabens (esters of 4-hydroxybenzoic acid), including the distinction between branched and linear isomers of propyl- and butyl-parabens and triclosan in water samples, was developed and evaluated. The procedure includes in-sample acetylation-non-porous membrane-assisted liquid–liquid extraction and large volume injection–gas chromatography–ion trap–tandem mass spectrometry. Different derivatisation strategies were considered, i.e. post-extraction silylation with N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide and in situ acylation with acetic anhydride (Ac₂O) and isobutylchloroformate. Moreover, acceptor solvent and the basic catalyser of the acylation reaction were investigated. Thus, in situ derivatisation with Ac₂O and potassium hydrogenphosphate (as basic catalyser) was selected. Potassium hydrogenphosphate overcomes some drawbacks of other basic catalysers, e.g. toxicity and bubble formation, while leads to higher responses. Subsequently, other experimental variables affecting derivatisation–extraction yield such as pre-stirring time, salt addition and volume of Ac₂O were optimised by an experimental design approach. Under optimised conditions, the proposed method achieved detection limits from 0.1 to 1.4 ng L⁻¹ for a sample volume of 18 mL and extraction efficiencies, estimated by comparison with liquid–liquid extraction, between 46% (for methyl- and ethyl-parabens) and 110% (for benzylparaben). The reported sample preparation approach is free of matrix effects for parabens but affected for triclosan with a reduction of ≈ 40% when wastewater samples are analysed; therefore, both internal and external calibration can be used as quantification techniques for parabens, but internal standard calibration is mandatory for triclosan. The application of the method to real samples revealed the presence of these compounds in raw wastewater at concentrations up to 26 ng mL⁻¹, the prevalence of the linear isomer of propylparaben (n-PrP), and the coexistence of the two isomers of butylparaben (i-BuP and n-BuP) at similar levels.     

Fast and selective extraction of nicotine from human plasma based on magnetic strong cation exchange resin followed by liquid chromatography-tandem mass spectrometry

In the study, a fast and selective method based on magnetic separation has been developed for the extraction of nicotine from human plasma using magnetic strong cation exchange (MSCX) resins as adsorbent. MSCX resins were prepared using hydrophobic Fe₃O₄ magnetite as magnetically susceptible component, styrene and acrylic acid as polymeric matrix components, and acetyl sulfonate as the sulfonation agent. The extraction procedure was carried out in a single step by stirring the mixture of diluted plasma sample and MSCX resins in the vortex for 5 min. Then, the resins with adsorbed nicotine were separated from the sample matrix by applying an appropriate magnetic field. Main factors affecting the extraction of nicotine such as the amount of MSCX resins, pH value of the extraction solvent, extraction time, and washing and eluting conditions were optimized. The nicotine eluted from the resins was determined by liquid chromatography–tandem mass spectrometry. The calibration curve obtained by analyzing matrix-matched standards shows excellent linear relationship (r ² = 0.9998) in the concentration range of 10–2,500 ng mL⁻¹. The limit of detection and quantification obtained are 2.9 and 9.7 ng mL⁻¹, respectively. The relative standard deviations of intra- and inter-day obtained are in the range of 1.9–6.9% and 2.5–7.8% with the recoveries ranging from 78.7% to 99.1%. The proposed method was successfully applied to determine nicotine in human plasma phlebotomized from ten male smokers. Nicotine was detectable with the contents ranging from 44.4 to 221.9 ng mL⁻¹ in five samples.     

Determination of organophosphorus pesticides in environmental water samples by dispersive liquid–liquid microextraction with solidification of floating organic droplet followed by high-performance liquid chromatography

A simple dispersive liquid–liquid microextraction based on solidification of floating organic droplet coupled with high-performance liquid chromatography–diode array detection was developed for the determination of five organophosphorus pesticides (OPs) in water samples. In this method, the extraction solvent used is of low density, low toxicity, and proper melting point near room temperature. The extractant droplet could be collected easily by solidifying it in the lower temperature. Some important experimental parameters that affect the extraction efficiencies were optimized. Under the optimum conditions, the calibration curve was linear in the concentration range from 1 to 200 ng mL⁻¹ for the five OPs (triazophos, parathion, diazinon, phoxim, and parathion-methyl), with the correlation coefficients (r) varying from 0.9991 to 0.9998. High enrichment factors were achieved ranging from 215 to 557. The limits of detection were in the range between 0.1 and 0.3 ng mL⁻¹. The recoveries of the target analytes from water samples at spiking levels of 5.0 and 50.0 ng mL⁻¹ were 82.2–98.8% and 83.6–104.0%, respectively. The relative standard deviations fell in the range of 4.4% to 6.3%. The method was suitable for the determination of the OPs in real water samples.     

Simplified cloud point extraction for the preconcentration of ultra-trace amounts of gold prior to determination by electrothermal atomic absorption spectrometry

A simple and sensitive cloud point extraction method has been developed for the preconcentration of ultra-trace amounts of gold as a prior step to its determination by electrothermal atomic absorption spectrometry. It is based on the extraction of gold in hydrochloric acid medium using the non-ionic surfactant polyethyleneglycolmono-p-nonylphenylether (PONPE 7.5) without adding a chelating agent. The preconcentration of a 50 mL sample solution was thus enhanced by a factor of 200. The resulting calibration graph was linear in the range of 10–200 ng L⁻¹ with a correlation coefficient of 0.9993. The limit of detection (3s) obtained under optimal conditions was 2.0 ng L⁻¹. The relative standard deviation for 10 replicate determinations at a 100 ng L⁻¹ Au level was 3.6%. The method was applied to the ultra-trace determination of gold in water and copper samples.     

Electrospun composite of polypyrrole-polyamide as a micro-solid phase extraction sorbent

A micro-solid phase extraction technique was developed using a novel polypyrrole-polyamide nanofiber sheet, fabricated by electrospinning method. The applicability of the new nanofiber sheet was examined as an extracting medium to isolate malathion as a model pesticide from aqueous samples. Solvent desorption was subsequently performed in a microvial, and an aliquot of extractant was injected into gas chromatography–mass spectrometry. Various parameters affecting the electrospinning process including monomer concentration, polyamide content, applied voltage, and electrospinning time were examined. After fabricating the most suitable preparation conditions, influential parameters on the extraction and desorption processes were optimized. The developed method proved to be rather convenient and offers sufficient sensitivity and good reproducibility. The limit of detection (S/N = 3) and limit of quantification (S/N = 10) of the method under optimized conditions were 50 and 100 ng L⁻¹, respectively. The relative standard deviation at concentration level of 1 ng mL⁻¹ was 2% (n = 3). The calibration curve of analyte showed linearity in the range of 0.1–1 ng mL⁻¹ (R ² = 0.9975). The developed method was successfully applied to tap and Zayanderood river water samples, while the relative recovery percentages of 98% and 96% were obtained, respectively. The whole procedure showed to be conveniently applicable and quite easy to be manipulated.     

Stir-bar-sorptive extraction and ultra-high-performance liquid chromatography–tandem mass spectrometry for simultaneous analysis of UV filters and antimicrobial agents in water samples

Stir-bar-sorptive extraction (SBSE) with liquid desorption (LD) and ultra-high-performance liquid chromatography–electrospray ionization triple-quadrupole tandem mass spectrometry (UHPLC–(ESI)MS–MS) were used for analysis of six personal care products in environmental water: four UV filters (2,2-dihydroxy-4-methoxybenzophenone, benzophenone-3, octocrylene, and octyldimethyl-p-aminobenzoic acid) and two antimicrobial agents (triclocarban and triclosan). Experimental conditions that affect SBSE-LD sorption efficiency (extraction time and temperature, sample pH, and ionic strength) and desorption efficiency (solvent, temperature, and time) were optimized. The method proved to be sensitive—a 50-mL sample was used to determine these compounds in environmental waters at trace levels. The detection limits of the analytical method were 2.5 ng L⁻¹ for river water and 5–10 ng L⁻¹ for effluent and influent sewage water. In river waters, benzophenone-3 was found at levels from 6 ng L⁻¹ to 28 ng L⁻¹ and triclosan at levels <LOQ. Benzophenone-3 was found between 75 and 127 ng L⁻¹ in influent sewage, whereas concentrations of benzophenone-3 and triclosan were commonly below 25 ng L⁻¹ in effluent sewage.     

Theoretical studies on anionic clusters of sulfate anions and carbon dioxide, SO 4?1/?2 (CO2)n, n?=?1?4

Geometry optimizations were performed on monoanionic and dianionic clusters of sulfate anions with carbon dioxide, SO₄^−1/−2(CO₂) _n , for n = 1–4, using the B3PW91 density functional method with the 6-311 + G(3df) basis set. Limited calculations were carried out with the CCSD(T) and MP2 methods. Binding energies, as well as adiabatic and vertical electron detachment energies, were calculated. No covalent bonding is seen for monoanionic clusters, with O₃SO–CO₂ bond distances between 2.8 and 3.0 ?. Dianionic clusters show covalent bonding of type [O₃S–O–CO₂]⁻², [O₃S–O–C(O)O–CO₂]⁻², and [O₂C–O–S(O₂)–O–CO₂]⁻², where one or two oxygens of SO₄⁻² are shared with CO₂. Starting with n = 2, the dianionic clusters become adiabatically more stable than the corresponding monoanionic ones. Comparison with SO₄^−1/−2(SO₂) _n and CO₃^−1/−2(SO₂) _n clusters, the binding energies are smaller for the present SO₄^−1/−2(CO₂) _n systems, while stabilization of the dianion occurs at n = 2 for both SO₄⁻²(CO₂) _n and SO₄⁻²(SO₂) _n , but only at n = 3 for CO₃⁻²(SO₂) _n .     

Dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry for the rapid and sensitive determination of UV filters in environmental water samples

The performance of the dispersive liquid–liquid microextraction (DLLME) technique for the determination of eight UV filters and a structurally related personal care species, benzyl salicylate (BzS), in environmental water samples is evaluated. After extraction, analytes were determined by gas chromatography combined with mass spectrometry detection (GC-MS). Parameters potentially affecting the performance of the sample preparation method (sample pH, ionic strength, type and volume of dispersant and extractant solvents) were systematically investigated using both multi- and univariant optimization strategies. Under final working conditions, analytes were extracted from 10 mL water samples by addition of 1 mL of acetone (dispersant) containing 60 μL of chlorobenzene (extractant), without modifying either the pH or the ionic strength of the sample. Limits of quantification (LOQs) between 2 and 14 ng L⁻¹, inter-day variability (evaluated with relative standard deviations, RSDs) from 9% to 14% and good linearity up to concentrations of 10,000 ng L⁻¹ were obtained. Moreover, the efficiency of the extraction was scarcely affected by the type of water sample. With the only exception of 2-ethylhexyl-p-dimethylaminobenzoate (EHPABA), compounds were found in environmental water samples at concentrations between 6 ± 1 ng L⁻¹ and 26 ± 2 ng mL⁻¹.     

<Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-Butylcalix[8]arene loaded silica gel for preconcentration of uranium(VI) via solid phase extraction

This paper reports silica gel loaded with p-tert-butylcalix[8]arene as a new solid phase extractor for determination of trace level of uranium. Effective extraction conditions were optimized in column methods prior to determination by spectrophotometry using arsenazo(III). The results showed that U(VI) ions can be sorbed at pH 6 in a mini-column and quantitative recovery of U(VI) (>95–98%) was achieved by stripping 0.4 mol L⁻¹ HCl. The sorption capacity of the functionalized sorbent is 0.072 mmol uranium(VI) g⁻¹ modified silica gel. The relative standard deviation and detection limit were 1.2% (n = 10) for 1 μg uranium(VI) mL⁻¹ solution and 0.038 μg L⁻¹, respectively. The method was employed to the preconcentration of U(VI) ions from spiked ground water samples.