Development of a fast liquid chromatography–tandem mass spectrometry method for the determination of endocrine-disrupting compounds in waters

A fast liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS-MS) method was developed to study five endocrine-disrupting compounds (4-n-nonylphenol, bisphenol A, estrone, 17β-estradiol and 17α-ethinylestradiol) in water. Different columns were tested; the chromatographic separation of the analytes was optimized on a Pinnacle DB biphenylic column with a water–acetonitrile gradient elution, which allowed the separation of the selected endocrine-disrupting compounds (EDCs) in less than 6 min. Quantitative analysis was performed in selected reaction monitoring (SRM) mode; two transitions were chosen for each compound, using the most abundant for quantitation. Calibration curves using bisphenol A-d ₁₆ as internal standard were drawn, showing good correlation coefficients (0.9993–0.9998). All figures of merit of the method were satisfactory; limits of detection were in the low pg range for all analytes. The method was then applied to the determination of the analytes in real water samples: to this aim, polar organic chemical integrative samplers (POCIS) were deployed in the influent and in the effluent of a drinking water treatment plant in Liguria (Italy). The EDC level was rather low in the influent and negligible in the outlet, reflecting the expected function of the treatment plant.     

Picogram determination of estrogens in water using large volume injection gas chromatography–mass spectrometry

In this study, a simple and efficient large volume injection gas chromatography–mass spectrometry (GC-MS) method, via a programmable-temperature vaporizer (PTV) inlet, has been developed and applied in the determination of estrogens in environmental water samples without a prior derivatization process. Three commonly used estrogens estrone, 17 β-estradiol and 17 α-ethynylestradiol were selected as target compounds for this study. It has been demonstrated that the type of gas chromatograph liner and the initial inlet temperature can greatly affect the response intensity of estrogens. Three different types of PTV liners have been studied; the multibaffle liner generated the strongest response intensities towards the estrogen analytes. The results showed that the response intensities of estrogens reduced sharply while the initial inlet temperature increased. Various instrument conditions and sample preparation methods were studied in detail. The optimized method has been validated with good linearity, precision and accuracy. The method detection limit of each estrogen was found to be 0.041 ng/L for estrone, 0.046 ng/L for 17 β-estradiol and 0.031 ng/L for 17 α-ethynylestradiol. To the best of our knowledge, these results represent the best sensitivities achieved for estrogens analyzed in water samples via traditional GC-MS method without a derivatization process. This method has been successfully applied in the analyses of different water samples.     

Novel approaches to the analysis of steroid estrogens in river sediments

A wide range of estrogenic contaminants has been detected in the aquatic environment. Among these, natural and synthetic steroid estrogens, typically present in municipal sewage-treatment plant (STP) effluents, are the most potent. In this study a new GC–MS method has been developed for direct analysis of five major steroid estrogens (estrone, 17β-estradiol, 17α-ethinylestradiol, dienestrol, and diethylstilbestrol) in river sediments. Four GC–MS systems used for analysis of underivatized analytes in purified extracts were compared. Relatively low detection limits (1.5–5 ng g⁻¹ dried sediment) and good repeatability of GC splitless injection (RSD 1–2%) were achieved by use of a system combining low-pressure gas chromatography with a single-quadrupole mass analyzer (LP-GC–MS). Use of orthogonal gas chromatography (GC×GC) hyphenated with high-speed time-of-flight mass spectrometry (HSTOF-MS) enabled not only significantly better resolution of target analytes, and their unequivocal identification, but also further improvement (decrease) of their detection limits. In addition to these outcomes, use of this unique GC×GC–TOF-MS system enabled identification of several other non-target chemicals, including pharmaceutical steroids, present in purified sediment extracts.     

Solid phase analytical derivatization of anthropogenic and natural phenolic estrogen mimics with pentafluoropyridine for gas chromatography-mass spectrometry

A simple, low cost, fast and sensitive method is reported for the determination of the four endocrine disrupting chemicals (EDCs) 4-tert-butylphenol, 4-tert-octylphenol, bisphenol A and 17β-estradiol using pentafluoropyridine as the derivatizing reagent. These EDCs were determined by simultaneous extraction and derivatization in a solid phase analytical derivatization (SPAD) technique without the aid of any phase transfer catalyst (PTC) or an ion-pair mechanism. Recoveries of analytes as their tetrafluoropyridyl derivatives from water ranged from 71% for 4-tert-butylphenol to 106% for 17β-estradiol; from urine they ranged from 61% for 17β-estradiol to 91% for 4-tert-octylphenol; and from humic acids solution the ranged from 59% for 17β-estradiol to 104% for 4-tert-octylphenol in humic acid solutions. Calibration curves were constructed from a matrix of human male urine in the range 1-40 ng/mL and had coefficients of correlation greater than 0.99. For 4-tert-butylphenol, bisphenol A and 17β-estradiol the limits of quantitation were 5 ng/mL and for 4-tert-octylphenol it was 1 ng/mL. This method was applied to determine EDCs and detected 4-tert-octylphenol, bisphenol A and 17β-estradiol in concentrations comparable to those found in the literature. The method offers advantages in speed of analysis, reduced reagent and specificity of derivatization.     

Solid-phase extraction using molecularly imprinted polymer for selective extraction of natural and synthetic estrogens from aqueous samples

A method is proposed for the clean-up and preconcentration of natural and synthetic estrogens from aqueous samples employing molecularly imprinted polymer (MIP) as selective sorbent for solid-phase extraction (SPE). The selectivity of the MIP was checked toward several selected natural and synthetic estrogens such as estrone (E1), 17β-estradiol (β-E2), 17α-estradiol (α-E2), estriol (E3), 17α-ethinylestradiol (EE2), dienestrol (DIES) and diethylstilbestrol (DES). Ultrahigh pressure liquid chromatography (UHPLC) coupled to a TSQ triple quadrupole mass spectrometry (QqQ) was used for analysis of target analytes. The chromatographic separation of the selected compounds was performed in less than 2 min under isocratic conditions. The method was applied to the analysis of estrogens in spiked river and tap water samples. High recoveries (>82%) for estrone, 17β-estradiol, 17α-estradiol, estriol and 17α-ethinylestradiol were obtained. Lower but still satisfactory recoveries (>48%) were achieved for dienestrol and diethylstilbestrol. The method was validated and found to be linear in the range 50-500 ng L(-1) with correlation coefficients (R(2)) greater than 0.995 and repeatability relative standard deviation (RSD) below 8% in all cases. For analysis of 100-mL sample, the method detection limits (LOD) ranged from 4.5 to 9.8 ng L(-1) and the limit of quantitation (LOQ) from 14.9 to 32.6 ng L(-1). To demonstrate the potential of the MIP obtained, a comparison with commercially available C(18) SPE was performed. Molecularly imprinted SPE showed higher recoveries than commercially available C(18) SPE for most of the compounds. These results showed the suitability of the MIP-SPE method for the selective extraction of a class of structurally related compounds such as natural and synthetic estrogens.     

Determination of steroid hormones in blood by GC–MS/MS

This paper presents the development, optimization and validation of a methodology to determine nine key steroid hormones (viz. pregnenolone, progesterone, dehydroepiandrosterone, androstenedione, testosterone, dihydrotestosterone, estrone, 17α-estradiol and 17β-estradiol) expressed in the steroidogenesis in biological fluids. The analytical method allows for the determination of steroid hormones in blood plasma and serum down to 0.08–0.16 ng/mL for estrogens, 0.20–0.36 ng/mL for androgens and 0.36–0.43 ng/mL for progestagens. These limits of detection were obtainable using a two-step solid-phase clean-up for fractionation and elimination of interfering lipids (fatty acids, phospholipids, glycerides and sterols) from the steroid hormones. The accuracy of the method was 50–112% in the range 0.10 to 2.00 ng/mL.     

Determination of environmental estrogens in human urine by high performance liquid chromatography after fluorescent derivatization with p-nitrobenzoyl chloride

A high performance liquid chromatographic method (HPLC) for the simultaneous determination of 4-nonylphenol, bisphenol A, 17α-ethinylestradiol and three endogenic estrogens including 17α-estradiol, 17β-estradiol, estriol in urine sample, based on precolumn derivatization with p-nitrobenzoyl chloride, is presented in this paper. The estrogens mentioned above in urine were firstly hydrolyzed with 0.6 mol/l HCl, and then enriched and cleaned-up by ENV-18 C18 solid phase extraction (SPE) column. The estrogens on column were eluted with dichloromethane, and the eluent was evaporated to dryness under gentle nitrogen flow. The residue was allowed to react with p-nitrobenzoyl chloride at 25 °C for 30 min. Separation was performed on a C18 column with gradient elution using acetonitrile and water as mobile phase. A fluorescence detection system was used to detect the fluorescent derivatization products. The detection limit of the method was 2.7 μg/l for bisphenol A and 17β-estradiol, 2.9 μg/l for 4-nonylphenol, 4.6 μg/l for 17α-estradiol and 17α-ethinylestradiol and 8.3 μg/l for estriol, respectively. The relative standard deviations (R.S.D.) ranged from 1.29 to 4.52% and the recoveries ranged from 85.5 to 99.9%. The method was applied to the determination of those six estrogens mentioned above in human urine samples collected from 20 healthy volunteers (aged 21-29). Bisphenol A (BPA) and 4-nonylphenol (NP) were detected with average contents of 1.22 ± 1.38 mg/l and 0.38 ± 0.77 mg/l in 10 male urine samples and 1.29 ± 1.22 mg/l and 0.05 ± 0.05 mg/l in 10 female urine samples, respectively. 17α-ethinylestradiol (α-EE2) was also detected with average contents of 0.13 ± 0.41 mg/l and 0.06 ± 0.15 mg/l in male and female urine samples, respectively.     

Simultaneous identification and quantification of bisphenol A and 12 bisphenol analogues in environmental samples using precolumn derivatization and ultra high performance liquid chromatography with tandem mass spectrometry

A method for the identification and quantification of bisphenol A and 12 bisphenol analogues in river water and sediment samples combining liquid–liquid extraction, precolumn derivatization, and ultra high‐performance liquid chromatography coupled with tandem mass spectrometry was developed and validated. Analytes were extracted from the river water sample using a liquid–liquid extraction method. Dansyl chloride was selected as a derivatization reagent. Derivatization reaction conditions affecting production of the dansyl derivatives were tested and optimized. All the derivatized target compounds were well separated and eluted in 10 min. Dansyl chloride labeled compounds were analyzed using a high‐resolution mass spectrometer with electrospray ionization in the positive mode, and the results were confirmed and quantified in the parallel reaction monitoring mode. The method validation results showed a satisfactory level of sensitivity. Linearity was assessed using matrix‐matched standard calibration, and good correlation coefficients were obtained. The limits of quantification for the analytes ranged from 0.005 to 0.02 ng/mL in river water and from 0.15 to 0.80 ng/g in sediment. Good reproducibility of the method in terms of intra‐ and interday precision was achieved, yielding relative standard deviations of less than 10.1 and 11.6%, respectively. Finally, this method was successfully applied to the analysis of real samples.     

Membrane-assisted solvent extraction coupled to large volume injection–gas chromatography–mass spectrometry for the determination of a variety of endocrine disrupting compounds in environmental water samples

Membrane-assisted solvent extraction coupled to large volume injection in a programmable temperature vaporisation injector using gas chromatography–mass spectrometry analysis was optimised for the simultaneous determination of a variety of endocrine disrupting compounds in environmental water samples (estuarine, river and wastewater). Among the analytes studied, certain hormones, alkylphenols and bisphenol A were included. The nature of membranes, extraction solvent, extraction temperature, solvent volume, extraction time, ionic strength and methanol addition were evaluated during the optimisation of the extraction. Matrix effects during the extraction step were studied in different environmental water samples: estuarine water, river water and wastewater (influent and effluent). Strong matrix effects were observed for most of the compounds in influent and effluent samples. Different approaches were studied in order to correct or minimise matrix effects, which included the use of deuterated analogues, matrix-matched calibration, standard addition calibration, dilution of the sample and clean-up of the extract using solid-phase extraction (SPE). The use of deuterated analogues corrected satisfactorily matrix effect for estuarine and effluent samples for most of the compounds. However, in the case of influent samples, standard addition calibration and dilution of the sample were the best approaches. The SPE clean-up provided similar recoveries to those obtained after correction with the corresponding deuterated analogue but better chromatographic signal was obtained in the case of effluent samples. Method detection limits in the 5–54 ng L⁻¹ range and precision, calculated as relative standard deviation, in the 2–25% range were obtained.     

Targeted analysis of sphingoid precursors in human biofluids by solid-phase extraction with in situ derivatization prior to μ-LC-LIF determination

A method for determination of two relevant sphingoid precursors such as sphingosine and sphinganine and the corresponding conjugates sphingosine 1-phosphate and sphinganine 1-phosphate in human urine and serum is here presented. The method is characterized by a solid- phase extraction step with in situ derivatization of the sphingolipids in the eluate (o-phthaldialdehyde derivatives) to obtain fluorescent compounds. In this way, sample preparation was completely performed in a single automated step by means of a lab-on-valve system. Derivatized analytes were injected into a liquid chromatography system operating at micro regime and detected by laser-induced fluorescence. For determination of sphingoid phosphates, they were enzymatically converted to free sphingoids to obtain stable fluorescent derivatives. The detection limits were in the range 4.2–10.2 ng mL⁻¹ for serum and 0.56–1.36 ng mL⁻¹ for urine, with repeatability ranging from 3.9% to 6.2% expressed as relative standard deviation. The method was validated by direct infusion tandem mass spectrometry in multiple reaction monitoring to compare results provided by analysis of biofluids and to confirm the identity of the target compounds. Sensitivity and precision were better than or similar to those provided by the confirmatory method. The automation of sample preparation enables to scale-down this step and improves precision by minimization of human intervention, being thus suitable for clinical analysis.     

Reversed-phase liquid chromatography coupled on-line to estrogen receptor bioaffinity detection based on fluorescence polarization

We describe the development and validation of a high-resolution screening (HRS) platform which couples gradient reversed-phase high-performance liquid chromatography (RP-HPLC) on-line to estrogen receptor α (ERα) affinity detection using fluorescence polarization (FP). FP, which allows detection at high wavelengths, limits the occurrence of interference from the autofluorescence of test compounds in the bioassay. A fluorescein-labeled estradiol derivative (E2-F) was synthesized and a binding assay was optimized in platereader format. After subsequent optimization in flow-injection analysis (FIA) mode, the optimized parameters were translated to the on-line HRS bioassay. Proof of principle was demonstrated by separating a mixture of five compounds known to be estrogenic (17β-estradiol, 17α-ethinylestradiol and the phytoestrogens coumestrol, coumarol and zearalenone), followed by post-column bioaffinity screening of the individual affinities for ERα. Using the HRS-based FP setup, we were able to screen affinities of off-line-generated metabolites of zearalenone for ERα. It is concluded that the on-line FP-based bioassay can be used to screen for the affinity of compounds without the disturbing occurrence of autofluorescence.     

Trimethylsilyldiazomethane derivatization coupled with solid-phase extraction for the determination of alendronate in human plasma by LC-MS/MS

Alendronate is an important representative of bisphosphonates, strongly polar compounds that lack chromophores. With rare exceptions, derivatization of the analytes is necessary for bioanalysis. In this study, a rapid liquid chromatography–tandem mass spectrometry method employing pre-column derivatization was developed and validated for the determination of alendronate concentrations in human plasma. The procedure was based on derivatization with trimethylsilyldiazomethane during solid-phase extraction on a weak anion-exchange solid-phase cartridge, which integrated sample purification and derivatization into one step. The alendronate derivative was eluted with methanol. Chromatographic separation was performed on a Capcell PAK-C18 column. The total run time was 6.5 min. The calibration curve was linear in the range 1.00–1,000 ng/mL using d6-alendronate as the internal standard. The lower limit of quantification was 1.00 ng/mL. The intra- and inter-assay precision (in RSD) calculated from quality control samples was less than 15%, and the accuracy was between 98.1% and 100.2%. The validated method was successfully applied to characterize the pharmacokinetic profiles of alendronate following the intravenous infusion of 5 or 10 mg alendronate sodium to healthy volunteers.     

Application of multiwall carbon nanotubes-based matrix solid phase dispersion extraction for determination of hormones in butter by gas chromatography mass spectrometry

The multiwall carbon nanotubes (MWCNTs)-based matrix solid phase dispersion (MSPD) was applied for the extraction of hormones, including 17-α-ethinylestradiol, 17-α-estradiol, estriol, 17-β-estradiol, estrone, medroxyprogesterone, progesterone and norethisterone acetate in butter samples. The method includes MSPD extraction of the target analytes from butter samples, derivatization of hormones with heptafluorobutyric acid anhydride-acetonitrile mixture, and determination by gas chromatography-mass spectrometry. The mixture containing 0.30 g graphitized MWCNTs and 0.10 g MWCNTs was selected as absorbent. Ethyl acetate was used as elution solvent. The elution solvent volume and flow rate were 12 mL and 0.9 mL min(-1), respectively. The recoveries of hormones obtained by analyzing the five spiked butter samples were from 84.5 to 111.2% and relative standard deviations from 1.9 to 8.9%. Limits of detection and quantification for determining the analytes were in the range of 0.2-1.3 and 0.8-4.5 μg kg(-1), respectively. Compared with other traditional methods, the proposed method is simpler in the operation and shorter in the sample pretreatment time.     

An SPME–GC–MS method using an octadecyl silica fibre for the determination of the potential angiogenesis modulators 17β-estradiol and 2-methoxyestradiol in culture media

A simple and easily automable method based on solid-phase microextraction followed by gas chromatographic–mass spectrometric analysis was developed for the determination of two potential angiogenesis modulators 17β-estradiol (17-BE) and 2-methoxyestradiol (2-MEOE) in culture media. Trifluoroacetic anhydride was used as the derivatising agent. A homemade octadecyl silica coating, characterised by a coating thickness of 72 ± 10 μm and a good thermal stability until 250 °C, was prepared. Experimental design was used to optimise the extraction conditions in terms of derivatisation time, derivatisation temperature and time of extraction. As for method validation, lower limits of quantification of 0.17 and 0.015 μg/l for 17β-estradiol and 2-methoxyestradiol, respectively, were obtained. Finally, the capabilities of the developed fibres were evaluated for the analysis of the investigated analytes developed by granulosa cells in culture media maintained under normoxic, hypoxic and anoxic conditions, in order to better elucidate their possible role in the angiogenic process. An increase of the production of both 17-BE and 2-MEOE in hypoxic and anoxic conditions seems to be related to the effect of oxygen deprivation.     

Analysis of hormonal steroids in fish plasma and bile by coupling solid-phase extraction to GC/MS

An analytical procedure for the simultaneous determination of twelve endogenous steroids (testosterone, androstenedione, 17β-estradiol, estrone, pregnenolone, progesterone, dihydroandrostenedione, dihydrotestosterone, 11α-ketotestosterone, 17α-hydroxyprogesterone, 17α-hydroxypregnenolone, 17α,20β-dihydroxy-4-pregnen-3-one) in plasma and bile samples by solid-phase extraction (SPE) and gas chromatography/mass spectrometry (GC–MS) has been developed. After enzymatic hydrolysis for bile samples only, samples were concentrated and purified using two successive SPE (C₁₈ and NH₂) cartridges. Analytes were derivatized with a mixture of N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA) / mercaptoethanol / ammonium iodide (NH₄I) and determined by GC–MS in selective ion monitoring mode. For most of the steroids monitored, recoveries were in the range 90–120% in plasma and in the range 60–70% in bile, and the reproducibility was below 10% for the complete procedure. Limits of detection obtained ranged from 0.1 to 0.4 ng/g in fish plasma and from 1.6 to 14 ng/g in fish bile. The developed method was successfully applied to the determination of plasma steroids in flounders (Platichthys flesus) collected from two French estuaries.     

Simultaneous determination of hexabromocyclododecane, tetrabromobisphenol A, and related compounds in sewage sludge and sediment samples from Ebro River basin (Spain)

This paper describes the development of a methodology for the simultaneous determination and quantification of hexabromocyclododecane (HBCD), tetrabromobisphenol A (TBBPA), and related compounds (bisphenol A, monobromobisphenol A, dibromobisphenol A, and tribromobisphenol A) in sludge and sediment samples. The selected method is based on an extraction with dichloromethane: methanol followed by purification via SPE C₁₈ cartridges. Instrumental determination was carried out by liquid chromatography–quadrupole linear ion trap mass spectrometry (LC-QqLIT-MS), with quantification based on isotopic dilution method. Analyte recoveries were in the range of 39–120% and 88–126% for spiked sewage and sediment, respectively. Repeatability of replicate extractions was better than 13% relative standard deviation. Linearity was checked in the range of 0.05 and 25 injected nanograms. Limits of detection (LODs) and limits of quantification (LOQs) were in the range of 0.6 and 2.7 ng/g and 1.4 and 66 ng/g for sediment and sludge samples, respectively. The developed method was applied to sewage sludge and sediment samples collected along the Ebro River and Cinca River, one of its tributaries (northeast of Spain). TBBPA levels in sewage sludge ranged from not quantified to 1,329 ng/g dw, whereas levels in sediment samples were lower, between not detected and 15 ng/g dw. As regards HBCD, concentrations were between not detected and 375 ng/g for sludge samples and 0.8 and 1850 ng/g for sediments.     

Determination of basic drugs of abuse in human serum by online extraction and LC–MS/MS

A new quantitation method for the determination of drugs of abuse (opiates, amphetamine and derivatives, cocaine, methadone and metabolites) in serum by using online extraction coupled to liquid chromatography (LC)–mass spectrometry (MS)/MS has been developed. The online extraction is carried out using two extraction columns simultaneously and one analytical column. One extraction column is loaded, while the other one is eluted by a gradient. The elution gradient also separates the analytes in the analytical column. For the sample preparation, serum is spiked with a mixture of deuterated analogues of the drugs. After protein precipitation with methanol/zinc sulphate, centrifugation, evaporation and reconstitution, the sample is injected into the LC system. The quantitation is based on the analysis of two multiple reaction monitoring transitions per drug. The recovery of the protein precipitation step is over 80% for all analytes. Intra- and interday precision, as relative standard deviation, is lower than 6%, and in the case of accuracy, RE is lower than 15%. Only the most polar analytes showed matrix effects. The limits of quantitation for the analysed compounds vary between 0.5 and 2.8 ng/mL. The developed method was used to quantify basic drugs in samples “from driving under the influence of drugs” cases. The results were compared with those obtained by using solid-phase extraction–GC–MS.     

Occurrence of endocrine-disrupting compounds in reclaimed water from Tianjin,China

Continuous disposal of endocrine-disrupting compounds (EDCs) into the environment can lead to serious human health problems and can affect plants and aquatic organisms. The determination of EDCs in water has become an increasingly important activity due to our increased knowledge about their toxicities, even at low concentration. The EDCs in water samples from the reclaimed water plant of Tianjin, northern China, were identified by gas chromatography (GC)–mass spectrometry (MS). Important and contrasting EDCs including estrone (E1), 17β-estradiol (E2), 17α-ethynylestradiol (EE2), 4-tert-octylphenol (OP), 4-nonylphenol (NP), bisphenol A (BPA), di-n-butyl phthalate (DnBP), diisobutyl phthalate (DIBP), and di(2-ethylhexyl)phthalate (DEHP) were selected as the target compounds. Concentrations of steroid hormones, alkylphenolic compounds and phthalates ranged from below the limit of detection (LOD) to 8.1 ng L⁻¹, from <LOD to 14.2 ng L⁻¹, and from 1.00 μg L⁻¹ to 23.8 μg L⁻¹, respectively. The average removal efficiencies for target EDCs varied from 30% to 82%. These results indicate that environmental endocrine disrupting compounds are not completely removed during reclaimed water treatment and may be carried over into the general aquatic environment.     

Simultaneous determination of selected estrogenic endocrine disrupting chemicals and bisphenol A residues in whole milk using fabric phase sorptive extraction coupled to HPLC‐UV detection and LC‐MS/MS

A simple and sensitive analytical methodology is developed for rapid screening and quantification of selected estrogenic endocrine disrupting chemicals and bisphenol A from intact milk using fabric phase sorptive extraction in combination with high‐performance liquid chromatography coupled to ultraviolet detection/tandem mass spectrometry. The new approach eliminates protein precipitation and defatting step from the sample preparation workflow. In addition, the error prone and time‐consuming solvent evaporation and sample reconstitution step used as the sample post‐treatment has been eliminated. Parameters with most significant impact on the extraction efficiency of fabric phase sorptive extraction including sorbent chemistry, sample volume, extraction time have been thoroughly studied and optimized. Separation of the selected estrogenic endocrine disrupting chemicals including α‐estradiol, hexestrol, estrone, 17α‐ethinyl estradiol, diethylstilboestrol, and bisphenol A were achieved using a Zorbax Extend‐C18 high‐performance liquid chromatography column (15 cm × 4.6 mm, 5 μm particle size). The limit of detection values obtained in fabric phase sorptive extraction with high‐performance liquid chromatography with ultraviolet detection ranged from 25.0 to 50.0 ng/mL. The method repeatability values were 3.6–13.9 (relative standard deviation, %) and intermediate precision values were 4.6–12.7 (relative standard deviation, %). The fabric phase sorptive extraction method was also coupled to liquid chromatography with tandem mass spectrometry for identifying each endocrine disrupting chemical at 10 ng/mL.     

Development of a stir bar sorptive extraction method coupled to solidification of floating droplets dispersive liquid–liquid microextraction based on deep eutectic solvents for the extraction of acidic pesticides from tomato samples

A stir bar sorptive extraction method coupled with deep eutectic solvent based solidification of floating organic droplets–dispersive liquid–liquid microextraction has been used for the simultaneous derivatization and extraction of some acidic pesticides in tomato samples. In this method, initially the analytes are adsorbed on a coated stir bar from tomato juice filled in a narrow tube. After extraction, the stir bar is removed and a water–miscible deep eutectic solvent is used to elute the analytes. Afterward, a derivatization agent and a water–immiscible deep eutectic solvent (as an extraction solvent) with melting point near to room temperature are added to the obtained eluant at µL–levels and the obtained mixture is rapidly injected into deionized water. Under the optimum conditions, the introduced method indicated high enhancement (1543–3353) and enrichment (2530–2999) factors, low limits of detection (7–14 ng/L) and quantification (23–47 ng/L), good linearity (r² ≥ 0.9982), and satisfactory repeatabilities (relative standard deviation ≤12% for intra– and inter–day precisions at a concentration of 100 ng/L of each analyte). Finally, the proposed method was applied in analysis of the analytes in tomato samples.