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.     

Determination of some carbamate pesticides in watermelon and tomato samples by dispersive liquid–liquid microextraction combined with high performance liquid chromatography

A novel method for the determination of five carbamate pesticides (metolcarb, carbofuran, carbaryl, isoprocard and diethofencard) in watermelon and tomato samples was developed by dispersive liquid–liquid microextraction (DLLME) coupled with high performance liquid chromatography-diode array detection (HPLC-DAD). Some experimental parameters that influence the extraction efficiency were studied and optimised to obtain the best extraction results. Under the optimum conditions for the method, the calibration curve was linear in the concentration range from 10 to 1000?ng?g^?1 for all the five carbamate pesticides, with the correlation coefficients (r) varying from 0.9982 to 0.9992. Good enrichment factors were achieved ranging between 80 and 177, depending on the compound. The limits of detection (LODs) (S/N?=?3) were ranged from 0.5 to 1.5?ng?g^?1. The method has been successfully applied to the analysis of the pesticide residues in watermelon and tomato samples. The recoveries of the method fell in the range between 76.2% to 94.5% with RSDs less than 9.6%, indicating the feasibility of the DLLME method for the determination of the five carbamate pesticides in watermelon and tomato samples.     

Determination of triazines in honey by dispersive liquid–liquid microextraction high-performance liquid chromatography

Dispersive liquid–liquid microextraction (DLLME) high-performance liquid chromatography (HPLC) was developed for extraction and determination of triazines from honey. A room temperature ionic liquid, 1-hexyl-3-methylimidazolium hexafluorophosphate [C₆MIM][PF_6.], was used as extraction solvent and Triton X 114 was used as dispersant. A mixture of 175 μL [C₆MIM][PF₆] and 50 μL 10% Triton X 114 was rapidly injected into the 20 mL honey sample by syringe. After extraction, phase separation was performed by centrifugation and the sedimented phase was analyzed by HPLC. Some experimental parameters, such as type and volume of extraction solvent, concentration of dispersant, pH value of sample solution, salt concentration and extraction time were investigated and optimized. The detection limits for chlortoluron, prometon, propazine, linuron and prebane are 6.92, 5.84, 8.55, 8.59 and 5.31 μg kg⁻¹, respectively. The main advantages of the proposed method are simplicity of operation, low cost, high enrichment factor and extraction solvent volume at microliter level. Honey samples were analyzed by the proposed method and obtained results indicated that the proposed method provides acceptable recoveries and precisions.     

Analysis of eight pyrethroids in water samples by liquid–liquid microextraction based on solidification of floating organic droplet combined with gas chromatography

A novel method was developed for the determination of eight pyrethroids in water samples by liquid–liquid microextraction based on solidification of floating organic droplets followed by gas chromatography with electron capture detection. The type and volume of the extraction solvents, extraction time, sample solution temperature, stirring rate and ionic strength were studied and optimized. Under the optimum conditions, enrichment factors ranged from 824 to 1,432, and the limit of detection range from 2.0 to 50 ng?L^?1. The calibration graph is linear from 0.15 to 80 μg?L^?1 for cyfluthrin, fenvalerate, fluvalinate and deltamethrin, 0.09 to 80 μg?L^?1 for fenpropathrin, 0.006 to 80 μg?L^?1 for lambda-cyhalothrin, 0.026 to 80 μg?L^?1 for permethrin, 0.01 to 80 μg?L^?1 for cypermethrin. The correlation coefficients (r) varied from 0.9961 to 0.9988. The method was successfully applied to the determination of pyrethroid pesticide residues in tap water, well water, reservoir water, and river water. Recoveries ranged from 79.0% to 113.6%, and relative standard deviations are between 4.1% and 8.7%.     

Determination of perfluorocarboxylic acids in water by ion-pair dispersive liquid–liquid microextraction and gas chromatography–tandem mass spectrometry with injection port derivatization

A novel technique for derivatization in a gas chromatograph injection port after a one-step extraction of trace perfluorocarboxylic acids (PFCAs) in water with ion pair formation during dispersive liquid–liquid microextraction (DLLME) was investigated. Tetrabutylammonium hydrogen sulfate (TBAHS) was used as the ion pair reagent. PFCA butyl ester derivatives were formed in the GC injection port and then analyzed using gas chromatography coupled to tandem mass spectrometry with negative chemical ionization. According to our analysis, the operative linear range for PFCA detection from 250 pg mL⁻¹ to 2 μg mL⁻¹ with a relative standard derivation (RSD) below 13%. Detection limits were achieved at the level of 37–51 pg mL⁻¹. This method was successfully applied for the analyzing of PFCAs in river water samples from urban and industrial areas without tedious pretreatment. The concentration range over which PFCAs were detected is from 0.6 ng mL⁻¹ to 604.9 ng mL⁻¹.     

Solvent-based de-emulsification dispersive liquid–liquid microextraction combined with gas chromatography–mass spectrometry for determination of trace organochlorine pesticides in environmental water samples

In this work, we propose solvent-based de-emulsification dispersive liquid–liquid microextraction (SD-DLLME) as a simple, rapid and efficient sample pretreatment technique for the extraction and preconcentration of organochlorine pesticides (OCPs) from environmental water samples. Separation and analysis of fifteen OCPs was carried out by gas chromatography–mass spectrometry (GC/MS). Parameters affecting the extraction efficiency were systematically investigated. The detection limits were in the range of 2–50 ng L⁻¹ using selective ion monitoring (SIM). The precision of the proposed method, expressed as relative standard deviation, varied between 3.5 and 10.2% (n = 5). Results from the analysis of spiked environmental water samples at the low-ppb level met the acceptance criteria set by the EPA.     

Determination of atranol and chloroatranol in perfumes using simultaneous derivatization and dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry

A new analytical method based on simultaneous derivatization and dispersive liquid–liquid microextraction (DLLME) followed by gas chromatography–mass spectrometry (GC–MS), for the determination of the allergenic compounds atranol and chloroatranol in perfumes, is presented. Derivatization of the target analytes by means of acetylation with anhydride acetic in carbonate buffer was carried out. Thereby volatility and detectability were increased for improved GC–MS sensitivity. In addition, extractability by DLLME was also enhanced due to a less polar character of the solutes. A liquid–liquid extraction was performed before DLLME to clean up the sample and to obtain an aqueous sample solution, free of the low polar matrix from the essential oils, as donor phase. Different parameters, such as the nature and volume of both the extraction and disperser solvents, the ionic strength of the aqueous donor phase or the effect of the derivatization reagent volume, were optimized. Under the selected conditions (injection of a mixture of 750 μL of acetone as disperser solvent, 100 μL of chloroform as extraction solvent and 100 μL of anhydride acetic as derivatization reagent) the figures of merit of the proposed method were evaluated. Limits of detection in the low ng mL⁻¹ range were obtained. Matrix effect was observed in real perfume samples and thus, standard addition calibration is recommended.     

Rapid and sensitive determination of biphenyl and biphenyl oxide in water samples using dispersive liquid–liquid microextraction followed by gas chromatography

A rapid and sensitive method has been developed for the determination of biphenyl and biphenyl oxide in water samples using dispersive liquid–liquid microextraction followed by gas chromatography. This method involves the use of an appropriate mixture of extraction solvent (8.0?µL tetrachloroethylene) and disperser solvent (1.0?mL acetonitrile) for the formation of cloudy solution in 5.0?mL aqueous sample containing biphenyl and biphenyl oxide. After extraction, phase separation was performed by centrifugation and biphenyl and biphenyl oxide in sedimented phase (5.0?±?0.3?µL) were determined by gas chromatography-flame ionisation (GC-FID) system. Type of extraction and disperser solvents and their volumes, salt effect on the extraction recovery of biphenyl and biphenyl oxide from aqueous solution have been investigated. Under the optimum conditions and without salt addition, the enrichment factors for biphenyl and biphenyl oxide were 819 and 785, while the extraction recovery were 81.9% and 78.5%, respectively. The linear range was (0.125–100?µg L^?1) and limit of detection was (0.015?µg?L^?1) for both analytes. The relative standard deviation (RSD, n?=?4) for 5.0?µg?L^?1 of analytes were 8.4% and 6.7% for biphenyl and biphenyl oxide, respectively. The relative recoveries of biphenyl and biphenyl oxide from sea, river water and refined water (Paksan company) samples at spiking level of 5.0?µg?L^?1 were between 85.0% and 100 %.     

Determination of UV filters in both soluble and particulate fractions of seawaters by dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry

An analytical method to determine the total content (i.e., not only in the soluble fraction but also in the particulate one) of eight commonly used UV filters in seawater samples is presented for the first time. Dispersive liquid–liquid microextraction (DLLME) is used as microextraction technique to pre-concentrate the target analytes before their determination by gas chromatography–mass spectrometry (GC–MS). In order to release the UV filters from the suspended particles an ultrasound treatment is performed before DLLME. The ultrasound treatment time was studied in order to achieve a quantitative lixiviation of the target analytes. The type and volume of both disperser and extraction solvent, the sample volume, the pH and the ionic strength involved in the DLLME have been optimized to provide the best enrichment factors. Under the optimized conditions, the method was successfully validated showing good linearity, enrichment factors between 112 and 263 depending on the analyte, limits of detection and quantification in the low ng L⁻¹ range (10–30 ng L⁻¹ and 33–99 ng L⁻¹, respectively) and good intra- and inter-day repeatability (RSD <15%). No significant matrix effects were found. Finally, the method was satisfactorily applied to the analysis of three seawater samples from different origin. Results showed significant amounts of UV filters in the particulate fraction that would have been ignored if only the soluble fraction had been considered. This fact shows that the UV filters are also accumulated in the suspended particles contained in water, what should be taken into account from an environmental standpoint.     

Determination of octylphenol and nonylphenol in aqueous sample using simultaneous derivatization and dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry

A simple and fast sample preparation method for the determination of nonylphenol (NP) and octylphenol (OP) in aqueous samples by simultaneous derivatization and dispersive liquid–liquid microextraction (DLLME) was investigated using gas chromatography–mass spectrometry (GC/MS). In this method, a combined dispersant/derivatization catalyst (methanol/pyridine mixture) was firstly added to an aqueous sample, following which a derivatization reagent/extraction solvent (methyl chloroformate/chloroform) was rapidly injected to combine in situ derivatization and extraction in a single step. After centrifuging, the sedimented phase containing the analytes was injected into the GC port by autosampler for analysis. Several parameters, such as extraction solvent, dispersant solvent, amount of derivatization reagent, derivatization and extraction time, pH, and ionic strength were optimized to obtain higher sensitivity for the detection of NP and OP. Under the optimized conditions, good linearity was observed in the range of 0.1–1000 μg L⁻¹ and 0.01–100 μg L⁻¹ with the limits of detection (LOD) of 0.03 μg L⁻¹ and 0.002 μg L⁻¹ for NP and OP, respectively. Water samples collected from the Pearl River were analyzed with the proposed method, the concentrations of NP and OP were found to be 2.40 ± 0.16 μg L⁻¹ and 0.037 ± 0.001 μg L⁻¹, respectively. The relative recoveries of the water samples spiked with different concentrations of NP and OP were in the range of 88.3–106.7%. Compared with SPME and SPE, the proposed method can be successfully applied to the rapid and convenient determination of NP and OP in aqueous samples.     

Determination of organochlorine pesticides in river water using dispersive liquid–liquid microextraction and gas chromatography–electron capture detection

Dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography–electron capture detection (GC–ECD), has been developed for the extraction and determination of 14 organochlorine pesticides (hexachlorocyclohexanes (α-HCH, β-HCH and δ-HCH), Lindane (γ-HCH), Aldrin, Dieldrin, Endrin, Heptachlor, Heptachlor epoxide, α-Chlordane, β-Chlordane and p,p′-DDT, p,p′-DDD, p,p′-DDE) in river water samples. Factors relevant to the microextraction efficiency, such as the kind of extraction and disperser solvent, their volume and the salt effect was investigated and optimised. In this method the appropriate mixture of extraction solvent (13.5 µL carbon disulphide) and disperser solvent (0.50 mL acetone) were rapidly injected into the aqueous sample by syringe. The values of the detection limit of the method were in the range of 0.05–0.001 µg L^?1, while the relative standard deviations for five replicates varied from 2.7 to 9.3%. A good linearity (0.9894 ≤ r ² ≤ 0.9998) and a broad linear range (0.01–200 µg L^?1) were obtained. The method exhibited enrichment factors ranging from 647 to 923, at room temperature. The relative standard deviations varied from 2.7 to 9.3% (n = 5). The relative recoveries of each pesticide from water samples at spiking levels of 2.00 and 10.0 µg L^?1 were 88.0–111.0% and 95.8–104.1%, respectively. Finally, the proposed method was successfully utilised for the preconcentration and determination of the organochlorine pesticides in the Jajrood River water samples.     

Comparison of dispersive liquid–liquid microextraction and hollow fiber liquid–liquid–liquid microextraction for the determination of fentanyl,alfentanil, and sufentanil in water and biological fluids by high-performance liquid chromatography

Dispersive liquid–liquid microextraction (DLLME) and hollow fiber liquid–liquid–liquid microextraction (HF-LLLME) combined with HPLC–DAD have been applied for the determination of three narcotic drugs (alfentanil, fentanyl, and sufentanil) in biological samples (human plasma and urine). Different DLLME parameters influencing the extraction efficiency such as type and volume of the extraction solvent and the disperser solvent, concentration of NaOH, and salt addition were investigated. In the HF-LLLME, the effects of important parameters including organic solvent type, concentration of NaOH as donor solution, concentration of H₂SO₄ as acceptor phase, salt addition, stirring rate, temperature, and extraction time were investigated and optimized. The results showed that both extraction methods exhibited good linearity, precision, enrichment factor, and detection limit. Under optimal condition, the limits of detection ranged from 0.4 to 1.9 μg/L and from 1.1 to 2.3 μg/L for DLLME and HF-LLLME, respectively. For DLLME, the intra- and inter-day precisions were 1.7–6.4% and 14.2–15.9%, respectively; and for HF-LLLME were 0.7–5.2% and 3.3–10.1%, respectively. The enrichment factors were from 275 to 325 and 190 to 237 for DLLME and HF-LLLME, respectively. The applicability of the proposed methods was investigated by analyzing biological samples. For analysis of human plasma and urine samples, HF-LLLME showed higher precision, more effective sample clean-up, higher extraction efficiency, lower organic solvent consumption than DLLME.     

Determination of bisphenol A and bisphenol B in canned seafood combining QuEChERS extraction with dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry

A new simple and reliable method combining an acetonitrile partitioning extractive procedure followed by dispersive solid-phase cleanup (QuEChERS) with dispersive liquid–liquid microextraction (DLLME) and further gas chromatography mass spectrometry analysis was developed for the simultaneous determination of bisphenol A (BPA) and bisphenol B (BPB) in canned seafood samples. Besides the great enrichment factor provided, the final DLLME extractive step was designed in order to allow the simultaneous acetylation of the compounds required for their gas chromatographic analysis. Tetrachloroethylene was used as extractive solvent, while the acetonitrile extract obtained from QuEChERS was used as dispersive solvent, and anhydride acetic as derivatizing reagent. The main factors influencing QuEChERS and DLLME efficiency including nature of QuEChERS dispersive-SPE sorbents, amount of DLLME extractive and dispersive solvents and nature and amount of derivatizing reagent were evaluated. DLLME procedure provides an effective enrichment of the extract, allowing the required sensitivity even using a single quadropole MS as detector. The optimized method showed to be accurate (>68?% recovery), reproducible (<21?% relative standard deviation) and sensitive for the target analytes (method detection limits of 0.2?μg/kg for BPA and 0.4?μg/kg for BPB). The screening of several canned seafood samples commercialized in Portugal (total?=?47) revealed the presence of BPA in more than 83?% of the samples with levels ranging from 1.0 to 99.9?μg/kg, while BPB was found in only one sample at a level of 21.8?μg/kg.     

Determination of hydroxylated benzophenone UV filters in sea water samples by dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry

A new analytical method for the determination of four hydroxylated benzophenone UV filters (i.e. 2-hydroxy-4-methoxybenzophenone (HMB), 2,4-dihydroxybenzophenone (DHB), 2,2′-dihydroxy-4-methoxybenzophenone (DHMB) and 2,3,4-trihydroxybenzophenone (THB)) in sea water samples is presented. The method is based on dispersive liquid–liquid microextraction (DLLME) followed by gas chromatography–mass spectrometry (GC–MS) determination. The variables involved in the DLLME process were studied. Under optimized conditions, 1000 μL of acetone (disperser solvent) containing 60 μL of chloroform (extraction solvent) were injected into 5 mL of aqueous sample adjusted to pH 4 and containing 10% NaCl. Before injecting into the GC–MS system, the DLLME extracts were evaporated under an air stream and then reconstituted with N,O-bis-(trimethylsilyl)trifluoroacetamide (BSTFA), thus allowing the target analytes to be converted into their trimethylsilyl derivatives. The best conditions for the derivatization reaction were 75 °C and 30 min. High enrichment factors for all the target analytes (ranging from 58 to 64) and good repeatability (RSD around 6%) were obtained. The limits of detection were in the range of 32–50 ng L⁻¹, depending on the analyte. The recoveries obtained by using the proposed DLLME–GC–MS method evidenced the presence of matrix effects for some of the target analytes, and thereby the standard addition calibration method was employed. Finally, the validated method was applied to the analysis of sea water samples.     

Rapid determination of pyridine derivatives by dispersive liquid–liquid microextraction coupled with gas chromatography/gas sensor based on nanostructured conducting polypyrrole

Polypyrrole (PPy) gas sensor has been prepared by polymerization of pyrrole on surfaces of commercial polymer fibers in the presence of an oxidizing agent. The sensing behavior of PPy gas sensor was investigated in the presence of pyridine derivatives. The resistive responses of the PPy gas sensor to pyridine derivatives were in the order of quinoline > pyridine > 4-methyl pyridine and 2-methyl pyridine. The PPy gas sensor was used as gas chromatography (GC) detector and exhibited linear responses to pyridine derivatives in the ranges 40–4000 ng. Dispersive liquid–liquid microextraction (DLLME) combined with GC/PPy gas sensor has been developed for simultaneous determination of pyridine derivatives and quinoline. The purposed method was used for determination of pyridine derivatives from cigarette smoke. The GC runs were completed in 4 min. The reproducibility of this method is suitable and good standard deviations were obtained. RSD value is less than 10% for all analytes.     

Determination of carbohydrates in tobacco by pressurized liquid extraction combined with a novel ultrasound-assisted dispersive liquid–liquid microextraction method

A novel derivatization-ultrasonic assisted-dispersive liquid–liquid microextraction (UA-DLLME) method for the simultaneous determination of 11 main carbohydrates in tobacco has been developed. The combined method involves pressurized liquid extraction (PLE), derivatization, and UA-DLLME, followed by the analysis of the main carbohydrates with a gas chromatography-flame ionization detector (GC-FID). First, the PLE conditions were optimized using a univariate approach. Then, the derivatization methods were properly compared and optimized. The aldononitrile acetate method combined with the O-methoxyoxime-trimethylsilyl method was used for derivatization. Finally, the critical variables affecting the UA-DLLME extraction efficiency were searched using fractional factorial design (FFD) and further optimized using Doehlert design (DD) of the response surface methodology. The optimum conditions were found to be 44 μL for CHCl₃, 2.3 mL for H₂O, 11% w/v for NaCl, 5 min for the extraction time and 5 min for the centrifugation time. Under the optimized experimental conditions, the detection limit of the method (LODs) and linear correlation coefficient were found to be in the range of 0.06–0.90 μg mL⁻¹ and 0.9987–0.9999. The proposed method was successfully employed to analyze three flue-cured tobacco cultivars, among which the main carbohydrate concentrations were found to be very different.     

Rapid determination of amide herbicides in environmental water samples with dispersive liquid–liquid microextraction prior to gas chromatography–mass spectrometry

This paper describes a novel, simple and environmentally friendly method for rapid determination of the amide herbicides metoalchlor, acetochlor, and butachlor. It is based on dispersive liquid-liquid microextraction and gas chromatography–mass spectrometry. Factors that may influence the enrichment efficiency, such as type and volume of extraction solvent, type and volume of dispersive solvent, extraction time, and content of NaCl, were investigated and optimized in detail. Under the optimum conditions, the limits of detection of metoalchlor, acetochlor, and butachlor were 0.02, 0.04, and 0.003 μg L⁻¹, respectively. The experimental results indicated that there was linearity over the range 0.1–50 μg L⁻¹ and good reproducibility with relative standard deviations over the range 1.6–3.0% (n = 5). The proposed method has been applied for the analysis of real-world water samples, and satisfactory results were achieved. Average recoveries of spiked herbicides were in the range 80.3–108.8%. All of these indicated that the developed method would be an efficient method for simultaneous determination of the three herbicides in environmental 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%.