Analysis of endocrine disruptor compounds in marine sediments by in cell clean up-pressurized liquid extraction-liquid chromatography tandem mass spectrometry determination

A less time-, solvent- and sorbent-consuming analytical methodology for the determination of bisphenol A and alkylphenols (4-tert-octylphenol, 4-octylphenol, 4-n-nonylphenol, nonylphenol) in marine sediment was developed and validated. The method was based on selective pressurized liquid extraction (SPLE) with a simultaneous in cell clean up combined with liquid chromatography-electrospray ionization tandem mass spectrometry in negative mode (LC-ESI-MS/MS). The SPLE extraction conditions were optimized by a Plackett–Burman design followed by a central composite design. Quantitation was performed by standard addition curves in order to correct matrix effects. The analytical features of the method were satisfactory: relative recoveries varied between 94 and 100% and repeatability and intermediate precision were <6% for all compounds. Uncertainty assessment of measurement was estimated on the basis of an in-house validation according to EURACHEM/CITAC guide. Quantitation limits of the method (MQL) ranged between 0.17 (4-n-nonylphenol) and 4.01 ng g⁻¹ dry weight (nonylphenol). Sensitivity, selectivity, automaticity and fastness are the main advantages of this green methodology. As an application, marine sediment samples from Galicia coast (NW of Spain) were analysed. Nonylphenol and 4-tert-octylphenol were measured in all samples at concentrations between 20.1 and 1409 ng g⁻¹ dry weight, respectively. Sediment toxicity was estimated and no risk to aquatic biota was found.     

Multiresidue analytical methods for the ultra-trace quantification of 33 priority substances present in the list of REACH in real water samples

Innovative and simultaneous multiresidue analytical methods of 33 multi-class pollutants in wastewaters, surface and ground waters, using solid phase extraction (SPE) followed by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) are presented. Target compounds include several groups of emerging and persistent contaminants derived from the European priority list of the registration evaluation and authorisation of chemicals system (REACH): organochlorine (8) and organophosphorus (2) pesticides, carbamates (2), fungicides (8), phthalates (2), alkylphenols (10) and bisphenol A.The recovery rates of the SPE gave levels ranged from 84 to 118% with exception of some compounds that yielded lower (methamidophos (50%), p,p′-DDT (60%) and o,p′-DDT (72%)) but all recoveries were acceptable. Low limits of detection (LOD) varied between 0.2 and 88.9 ng L⁻¹ (except for HPTE and 4n-octylphenol giving 161 and 220 ng L⁻¹, respectively). A study of matrix effects was performed in order to evaluate the best and reliable calibration approach.The developed analytical method was successfully applied to the analysis of the 33 substances in wastewater effluents as well as surface and ground waters. The most frequently detected families were alkylphenols and industrial endocrine disrupting compounds (phthalates and bisphenol A).     

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.     

Measurement of 4-nonylphenol and 4-tert-octylphenol in human urine by column-switching liquid chromatography-mass spectrometry

We report a method for determining 4-nonylphenol (NP) and 4-tert-octylphenol (OP) levels in human urine samples by column-switching liquid chromatography-electrospray mass spectrometry after enzymatic deglucuronidation. The method involves enzymatic deconjugation by β-glucuronidase and correction by the stable isotopically labeled internal standard, 4-(1-methyl)octylphenol-d₅. The compounds were separated by reversed-phase chromatography with a C₁₈ column, and detected by selected ion monitoring in the negative mode. After adding an internal standard to urine samples, a direct analysis was carried out. The average recoveries of OP and NP were above 85.0% with correction using the added internal standard. The quantitation limit in the urine samples was 0.3 ng ml⁻¹. The method enables the precise determination of standards and may be applied to the detection of trace amounts of OP and NP in human urine samples.     

Determination of Phenolic Endocrine Disruptors in Cosmetics by High-Performance Liquid Chromatography Mass Spectrometry

An analytical method for the simultaneous determination of bisphenol A, 4-t-octylphenol, 4-n-octylphenol, and 4-n-nonylphenol in cosmetic samples has been developed. These compounds have toxic effects on human health as they have shown to produce endocrine disrupting properties. Therefore, their presence in cosmetics should be avoided according to the current European Regulations on cosmetic products. The method is based on high-performance liquid chromatography coupled to mass spectrometry (HPLC-MS) detection. Standard addition calibration was used to avoid matrix effects. The limits of detection values ranged between 7 and 15?ng?mL^?1 (threefold of the residual standard deviation of regression lines). The proposed method was validated, and good recovery (90–106%) and repeatability values (2.7–8.2%) were obtained. Finally, the method was successfully applied to ten commercially available cosmetic samples. The good analytical features of the proposed method make it useful to carry out the quality control of cosmetic products and raw materials to assure the safety of users.     

Determination of bisphenol A, 4-n-nonylphenol, and 4-tert-octylphenol by temperature-controlled ionic liquid dispersive liquid-phase microextraction combined with high performance liquid chromatography-fluorescence detector

Present study described a simple, sensitive, and viable method for the determination of bisphenol A, 4-n-nonylphenol and 4-tert-octylphenol in water samples using temperature-controlled ionic liquid dispersive liquid-phase microextraction coupled to high performance liquid chromatography-fluorescence detector. In this experiment, 1-octyl-3-methylimidazolium hexafluorophosphate ([C₈MIM][PF₆]) was used as the extraction solvent, and bisphenol A, 4-n-nonylphenol and 4-tert-octylphenol were selected as the model analytes. Parameters affecting the extraction efficiency such as the volume of [C₈MIM][PF₆], dissolving temperature, extraction time, sample pH, centrifuging time and salting-out effect have been investigated in detail. Under the optimized conditions, good linear relationship was found in the concentration range of 1.0-100 μg L⁻¹ for BPA, 1.5-150 μg L⁻¹ for 4-NP, and 3-300 μg L⁻¹ for 4-OP, respectively. Limits of detection (LOD, S/N = 3) were in the range of 0.23-0.48 μg L⁻¹. Intra day and inter day precisions (RSDs, n = 6) were in the range of 4.6-5.5% and 8.5-13.3%, respectively. This method has been also successfully applied to analyze the real water samples at two different spiked concentrations and excellent results were obtained.     

Determination of some endocrine disrupter chemicals in urban wastewater samples using liquid chromatography-mass spectrometry

An analytical method for the simultaneous determination of trace amounts of fourteen endocrine disrupter chemicals (EDCs) in urban wastewater samples has been developed. The studied compounds were: bisphenol A and its chlorinated derivatives (monochloro, dichloro, trichloro and tretrachlorobisphenol A), three alkylphenols (4-n-nonyl, 4-n-octyl and 4-(tert-octyl)phenol) and six well known phthalate esters (dimethyl, diethyl, di-n-butyl, butylbenzyl, bis(2-ethylhexyl) and di-n-octylphthalate). The method involves extraction from the samples and preconcentration of the analytes using a solid-phase extraction (SPE) procedure and subsequent liquid chromatographic separation with mass spectrometric detection (LC−MS). Bisphenol F was used as a surrogate. Quantification limits found ranged between 12 ng L^− 1 for diethylphthalate and 69 ng L^− 1 for 4-(tert-octyl)phenol. The method was satisfactorily used for determination of these chemicals in urban wastewater samples of Granada City (Spain) and validated using a recovery assay with spiked samples.     

Focused ultrasound-assisted acceleration of enzymatic hydrolysis of alkylphenols and 17β-oestradiol glucuronide in fish bile

According to the European Water Framework Directive (WFD), alkylphenols, such as octylphenols and nonylphenols, and 17β-oestradiol are considered as priority or emerging pollutants, respectively, mainly due to their possible properties as endocrine-disrupting compounds (EDCs). EDCs are accumulated in liver, fat, kidney and bile in the glucuronide form. In order to determine the concentration of these compounds in bile, an enzymatic hydrolysis step is necessary. This step is usually long (～16 h), and in this sense, ultrasound probes were studied as a possible alternative energy source to accelerate this process. Enzymatic hydrolysis was reduced to 20 min using an ultrasound probe at one cycle and 10% of amplitude. For validation of analytical procedure, nonylphenol glucuronide (4NP-G), 4-tert-octylphenol glucuronide (4tOP-G) and 4-n-octylphenol glucuronide (4nOP-G) were synthesised while 17β-oestradiol glucuronide (E2-G) was commercially available. Bile from thick-lip grey mullets (Chelon labrosus) was spiked with known amounts of 4NP-G, 4tOP-G, 4nOP-G and E2-G and submitted to the optimised procedure. Good recoveries (77–122%), precision in the 5% to 12% range and limits of detection, ranging from the low nanogramme per gramme level for 4tOP, 4nOP and E2 to the low microgramme per gramme level for nonylphenols, were obtained. The optimised method was applied for the determination of alkylphenol in the bile of thick-lip grey mullets fish bile from the Urdaibai estuary (UNESCO reserve of the Biosphere, Bay of Biscay), and high concentrations (2.3–14.2 μg/g), such as those obtained in polluted areas, were measured. E2 was determined in the bile of thick-lip grey mullets, intraperitoneally injected with E2.     

Monitoring of environmental phenolic endocrine disrupting compounds in treatment effluents and river waters, Korea

The last two decades have witnessed growing scientific and public concerns over endocrine disrupting compounds (EDCs) that have the potential to alter the normal structure or functions of the endocrine system in wildlife and humans. In this study, the phenolic EDCs such as alkylphenol, chlorinated phenol and bisphenol A were considered. They are commonly found in wastewater discharges and in sewage treatment plant. In order to monitor the levels and seasonal variations of phenolic EDCs in various aquatic environments, a total of 15 water samples from the discharged effluent from sewage and wastewater treatment plants and river water were collected for 3 years. Ten environmental phenolic EDCs were determined by GC-MS and laser-induced fluorescence (LIF). GC-MS analysis revealed that most abundant phenolic EDCs were 4-n-heptylphenol, followed by nonlyphenol and bisphenol A during 2002-2003, while 4-t-butylphenol and 4-t-octylphenol were newly detected in aquatic environments in 2004.The category of phenolic EDCs showed similar fluorescence spectra and nearly equal fluorescence decay time. This makes it hard to distinguish each phenolic EDC from the EDCs mixture by LIF. Therefore, the results obtained from LIF analysis were expressed in terms of the fluorescence intensity of the total phenolic EDCs rather than that of the individual EDC. However, LIF monitoring and GC-MS analysis showed consistent result in that the river water samples had lower phenolic EDCs concentration compared to the effluent sample. This revealed a lower fluorescence intensity and the phenolic EDCs concentration in summer was lower than that in winter. For the validation of LIF monitoring for the phenolic EDCs, the correlation between EDCs concentration acquired from GC-MS and fluorescence intensity from LIF was obtained (R = 0.7379). This study supports the feasibility of the application of LIF into EDCs monitoring in aquatic systems.     

Confirmatory determination of organochlorine pesticides in surface waters using LC/APCI/tandem mass spectrometry⋄

A confirmatory method for the determination of organochlorine pesticides (OCPs) and their metabolites (endrin, α-endosulfan, β-endosulfan, endosulfan sulfate, heptachlor, heptachlor epoxide, 2,4′-DDD, 4,4′-DDD, 2,4′-DDE 4,4′-DDE, 2,4′-DDT, and 4,4′-DDT) in surface waters using liquid chromatography /APCI/tandem mass spectrometry has been developed. Chromatographic separation was carried out on a ChromSpher 5 Pesticide column using a gradient elution with mobile phase 1mM ammonium acetate-acetonitrile. Endrin, α-endosulfan, β-endosulfan , endosulfan sulfate, heptachlor and heptachlor epoxide were determined in the negative ionization mode, while the rest compounds in positive ionization mode. For the identification of the analytes, two multireaction monitoring transitions were selected per compounds except for the heptachlor which selected ion monitoring was used. The linearity of the optimized method ranges after SPE concentration, from 0.009 to 30.60 μgL⁻¹ with correlation coefficients greater than 0.99. The method recovery values varied from 72 to 119 % for the different fortification levels . The developed method was successfully applied to determine OCPs and their metabolites in surface water samples collected near paddy fields in growing season of rice, at year 2005 in Pathumthani province, Thailand. Endosulfan sulfate was detected in five out of seven samples and three of them could be quantitated in the range of 0.31to 0.50 μgL⁻¹.     

Evaluation of an hPXR reporter gene assay for the detection of aquatic emerging pollutants: screening of chemicals and application to water samples

Many environmental endocrine-disrupting compounds act as ligands for nuclear receptors. Among these receptors, the human pregnane X receptor (hPXR) is well described as a xenobiotic sensor to various classes of chemicals, including pharmaceuticals, pesticides, and steroids. To assess the potential use of PXR as a sensor for aquatic emerging pollutants, we employed an in vitro reporter gene assay (HG5LN-hPXR cells) to screen a panel of environmental chemicals and to assess PXR-active chemicals in (waste) water samples. Of the 57 compounds tested, 37 were active in the bioassay and 10 were identified as new PXR agonists: triazin pesticides (promethryn, terbuthryn, terbutylazine), pharmaceuticals (fenofibrate, bezafibrate, clonazepam, medazepam) and non co-planar polychlorobiphenyls (PCBs; PCB101, 138, 180). Furthermore, we detected potent PXR activity in two types of water samples: passive polar organic compounds integrative sampler (POCIS) extracts from a river moderately impacted by agricultural and urban inputs and three effluents from sewage treatment works (STW). Fractionation of POCIS samples showed the highest PXR activity in the less polar fraction, while in the effluents, PXR activity was mainly associated with the dissolved water phase. Chemical analyses quantified several PXR-active substances (i.e., alkylphenols, hormones, pharmaceuticals, pesticides, PCBs, bisphenol A) in POCIS fractions and effluent extracts. However, mass-balance calculations showed that the analyzed compounds explained only 0.03% and 1.4% of biological activity measured in POCIS and STW samples, respectively. In effluents, bisphenol A and 4-tert-octylphenol were identified as main contributors of instrumentally derived PXR activities. Finally, the PXR bioassay provided complementary information as compared to estrogenic, androgenic, and dioxin-like activity measured in these samples. This study shows the usefulness of HG5LN-hPXR cells to detect PXR-active compounds in water samples, and further investigation will be necessary to identify the detected active compounds.     

Off-Line Concentration of Bisphenol A and Three Alkylphenols by SPE then On-Line Concentration and Rapid Separation by Reverse-Migration Micellar Electrokinetic Chromatography

A method for separation of four environmentally important compounds (three alkylphenols and bisphenol A) by cyclodextrin-modified reverse-migration micellar electrokinetic chromatography (CD-RM-MEKC) has been optimized. On-line concentration, stacking using reverse-migrating micelles and a water plug (SRW), was used to improve the limit of detection. Two main factors affecting the efficiency of enhancement by SRW, injection sample length and water-plug length, are discussed in detail. Compared with the normal 2-s injection, more than 121-fold enhancement of peak area and more than 71-fold enhancement of peak height were achieved with 120-s sample injection after 120-s water-plug injection. With this optimized separation method and SRW technology, limits of detection were found to be 0.089, 0.030, 0.0091, and 0.033 mg L^–1 for 4-nonylphenol, 4-tert-octylphenol, bisphenol A, and 4-tert-butylphenol, respectively. Calibration plots (R² 0.9968) and relative standard deviations (RSD, %) of corrected peak areas and migration time were also satisfactory. Combined with off-line concentration by solid-phase extraction (SPE) this method might be used to determine these contaminants at ppb levels in groundwater samples.     

A novel fatty-acid-based in-tube dispersive liquid–liquid microextraction technique for the rapid determination of nonylphenol and 4-tert-octylphenol in aqueous samples using high-performance liquid chromatography–ultraviolet detection

In this study, a novel fatty-acid-based in-tube dispersive liquid–liquid microextraction (FA-IT-DLLME) technique is proposed for the first time and is developed as a simple, rapid and eco-friendly sample extraction method for the determination of alkylphenols in aqueous samples using high-performance liquid chromatography–ultraviolet detection (HPLC–UV). In this extraction method, medium-chain saturated fatty acids were investigated as a pH-dependent phase because they acted as either anionic surfactants or neutral extraction solvents based on the acid–base reaction caused solely by the adjustment of the pH of the solution. A specially designed home-made glass extraction tube with a built-in scaled capillary tube was utilized as the phase-separation device for the FA-IT-DLLME to collect and measure the separated extractant phase for analysis. Nonylphenol (NP) and 4-tert-octylphenol (4-tOP) were chosen as model analytes. The parameters influencing the FA-IT-DLLME were thoroughly investigated and optimized. Under the optimal conditions, the detector responses of NP and 4-tOP were linear in the concentration ranges of 5–4000 μg L⁻¹, with correlation coefficients of 0.9990 and 0.9996 for NP and 4-tOP, respectively. The limits of detection based on a signal-to-noise ratio of 3 were 0.7 and 0.5 μg L⁻¹, and the enrichment factors were 195 and 143 for NP and 4-tOP, respectively. The applicability of the developed method was demonstrated for the analysis of alkylphenols in environmental wastewater samples, and the recoveries ranged from 92.9 to 107.1%. The extraction process required less than 4 min and utilized only acids, alkalis, and fatty acids to achieve the extraction. The results demonstrated that the presented FA-IT-DLLME approach is highly cost-effective, simple, rapid and environmentally friendly in its sample preparation.     

Solid phase microextraction procedure for the determination of alkylphenols in water by on-fiber derivatization with N-tert-butyl-dimethylsilyl-N-methyltrifluoroacetamide

The solid phase microextraction (SPME) technique with on-fiber derivatization was evaluated for the analysis of alkylphenols (APs), including 4-tert-octylphenol (4-t-OP), technical nonylphenol isomers (t-NPs) and 4-nonylphenol (4-NP), in water. The 85 μm polyacrylate (PA) fiber was used and a two-step sample preparation procedure was established. In the first step, water sample of 2 mL was placed in a 4 mL PTFE-capped glass vial. Headspace extraction of APs in water was then performed under 65 °C for 30 min with 800 rpm magnetic stirring and the addition of 5% of sodium chloride. In the second step, the SPME fiber was placed in another 4 mL vial, which contained 100 μL of N-tert-butyl-dimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA) with 1% tert-butyl-dimethylchlorosilane (TBDMCS). Headspace extraction of MTBSTFA and on-fiber derivatization with APs were performed at 45 °C for 10 min. Gas chromatography/mass spectrometry (GC/MS) was used for the analysis of derivatives formed on-fiber. The adsorption-time profiles were also examined. The precision, accuracy and method detection limits (MDLs) for the analysis of all the APs were evaluated with spiked water samples, including detergent water, chlorinated tap water, and lake water. The relative standard deviations were all less than 10% and the accuracies were 100 ± 15%. With 2 mL of water sample, MDLs were in the range of 1.58-3.85 ng L⁻¹. Compared with other techniques, the study described here provided a simple, fast and reliable method for the analysis of APs in water.     

Accelerated solvent extraction then liquid chromatography coupled with mass spectrometry for determination of 4-t-octylphenol, 4-nonylphenols, and bisphenol A in fish liver

Summary Analysis of extracts from fish liver containing alkylphenol contaminants can be hindered by the presence of co-extracted fats and proteins that interfere with chromatographic analysis. In this study accelerated solvent extraction (ASE), Florisil clean-up, then combined liquid chromatography—mass spectrometry (LC-MS) with an electrospray (ESI) interface have been used to optimize an analytical procedure for the analysis of octylphenol, nonylphenol, and bisphenol A in fish liver. After comparison of the efficiency of ASE with conventional Soxhlet extraction the developed procedure was applied to the analysis of liver samples. Calibration plots of the relationship between concentration and the ratio of the responses to the analyte and to the internal standard, 4-n-nonylphenol, were determined by linear regression analysis over the concentration range 0.05 to 10 ppm and resulted in good fits (r ²>0.994). Recoveries (evaluated for each liver sample as the ratio between response to the surrogate compound, 4-n-nonylphenol, and that to the internal standard, 4-n-heptylphenol, relative to the same ratio for a reference standard solution) were 53±20%. Under the experimental conditions used in this work the limits of detection (LOD), calculated by use of a signal-to-noise ratio of 3∶1, were 5 ng g⁻¹ for 4-t-octylphenol, 15 ng g⁻¹ for bisphenol A, and 20 ng g⁻¹ for nonylphenol. The method can be satisfactorily applied to screening analysis of octyl-and nonylphenols and bisphenol A in biological samples such as fish liver.     

Analysis of Six Phenolic Endocrine Disrupting Chemicals in Surface Water and Sediment

An efficient and reliable method based on gas chromatography–mass spectrometry (GC–MS) was developed for the extraction and analysis of six phenolic endocrine disrupting chemicals (EDCs), such as 4-nonylphenol (4-NP), nonylphenol-mono-ethoxylate (NP1EO), nonylphenol-di-ethoxylate (NP2EO), 4-tert-octylphenol (4-t-OP), bisphenol A (BPA) and 4-cumylphenol (4-CP) in surface water and sediment. The method was developed by using microwave-assisted extraction (MAE), solid phase extraction (SPE) and derivatization procedure. The MAE procedures were performed by optimizing three key process factors, consisted of extraction solvent, extraction temperature and holding time, affecting the extraction efficiency from sediment samples. For SPE, various parameters that may affect the recovery efficiency of water samples, such as SPE phase cartridge, elution solvent, as well as pH of water samples, were investigated. A series of derivatization conditions, such as derivatization reagent, reaction temperature and reaction time, were improved. The method achieved good repeatability and reproducibility with relative standard deviations <13% for all target EDCs in the both samples. Satisfactory recoveries for spiked water and sediment samples ranged from 85 to 101% and 74 to 105%, respectively. The limits of quantification varied from 0.20 (4-t-OP) to 11.50 ng L^?1 (NP2EO) and from 0.31 (4-t-OP) to 9.50 ng g^?1 dry weight (dw) (NP2EO) for water samples and sediment samples, respectively. The established method was successfully applied to the analysis of target EDCs in surface water and sediment samples collected from Caohai site of Dianchi Lake, China. The results showed that NP1EO, NP2EO and BPA were the three dominant phenolic EDCs in the site, reaching 114, 97 and 149 ng L^?1 in surface water, while 444, 186 and 178 ng g^?1 dw in surface sediment, respectively.     

Determination of 4-nonylphenol and 4-tert.-octylphenol in water samples by stir bar sorptive extraction and thermal desorption-gas chromatography-mass spectrometry

A simple and highly sensitive method called thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS), which is used for the determination of trace amounts of 4-nonylphenol (NP) and 4-tert.-octylphenol (OP) in water samples, is described. NP and OP in samples are extracted from water samples and concentrated by the stir bar sorptive extraction (SBSE) technique. A stir bar coated with polydimethylsiloxane (PDMS) is added to a 2.0 ml water sample and stirring is carried out for 60 min at room temperature (25 °C) in a headspace vial. Then the extract is high sensitively analyzed by TD-GC-MS without any derivatization step. The optimum SBSE conditions are realized at an extraction time of 60 min. The detection limits are 0.02 ng ml⁻¹ for NP and 0.002 ng ml⁻¹ for OP. The method shows good linearity over the concentration range of 0.1-10 ng ml⁻¹ for NP and 0.01-10 ng ml⁻¹ for OP, and the correlation coefficients are higher than 0.999. The average recoveries of NP and OP are higher than 97% (R.S.D.: 3.6-6.2%) with correction using the added surrogate standards, 4-(1-methyl) octylphenol-d₅ and deuterium 4-tert.-octylphenol. This simple, accurate, sensitive and selective analytical method may be used in the determination of trace amounts of NP and OP in tap and river water samples.     

Solid-Phase Extraction/High-Performance Liquid Chromatography-Electrospray Mass Spectrometry to Determine Endocrine Disruptors in Water Samples

A method for determining a group of endocrine-disrupting compounds in water samples was developed. This method was based on high-performance liquid chromatography-(electrospray) mass spectrometry (HPLC-(ESI)MS), working in negative ionization (NI) mode. Solid-phase extraction (SPE) with 200 mg Lichrolut EN was used to preconcentrate the water samples. The performance of the method was tested with several environmental water samples such as river, marine and influent and effluent water from a sewage treatment plant (STP). The limits of detection (LODs) of the method were between 0.001 and 0.3 g L^–1 under selective-ion monitoring (SIM) acquisition mode for 500 mL of river, marine and STP effluent water samples and between 0.01 and 3 g L^–1 for 100 mL of STP influent water. We determined some endocrine disruptors, such as diuron, bisphenol A (BPA), estrone, 4-tert-butylphenol (4-t-BP), 4-tert-octylphenol (4-t-OP) and pentachlorophenol (PCP), in several water samples at levels of g L^–1.     

Development of a simple extraction and clean-up procedure for determination of organochlorine pesticides in soil using gas chromatography–tandem mass spectrometry

A procedure based on QuEChERS extraction and a simultaneous liquid–liquid partition clean-up was developed. The procedure involved extraction of hydrated soil samples using acetonitrile and clean-up by liquid–liquid partition into n-hexane. The hexane extracts produced were clean and suitable for determination using gas chromatography–tandem mass spectrometry (GC–MS/MS). The method was validated by analysis of soil samples, spiked at five levels between 1 and 200 μg kg⁻¹. The recovery values were generally between 70 and 100% and the relative standard deviation values (%RSDs) were at or below 20%. The procedure was validated for determination of 19 organochlorine (OC) pesticides. These were hexachlorobenzene (HCB), α-HCH, β-HCH, γ-HCH, heptachlor, heptachlor epoxide (trans), aldrin, dieldrin, chlordane (trans), chlordane (cis), oxychlordane, α-endosulfan, β-endosulfan, endosulfan sulfate, endrin, p,p′-DDT, o,p′-DDT, p,p′-DDD and p,p′-DDE. The method achieved low limits of detection (LOD; typically 0.3 μg kg⁻¹) and low limits of quantification (LOQ; typically 1.0 μg kg⁻¹). The method performance was also assessed using five fortified soil samples with different physico-chemical properties and the method performance was consistent for the different types of soil samples. The proposed method was compared with an established procedure based on Soxtec extraction. This comparison was carried out using six soil samples collected from regions of Pakistan with a history of intensive pesticide use. The results of this comparison showed that the two procedures produced results with good agreement. The proposed method produced cleaner extracts and therefore led to lower limits of quantification. The proposed method was less time consuming and safer to use. The six samples tested during this comparison showed that soils from cotton growing regions contained a number of persistent OC residues at relatively low levels (<10 μg kg⁻¹). These residues were α-HCH, γ-HCH, heptachlor, chlordane (trans), p,p′-DDT, o,p′-DDT, p,p′-DDD, p,p′-DDE, β-endosulfan and endosulfan sulfate.     

Optimisation of stir bar sorptive extraction and in-tube derivatisation-thermal desorption-gas chromatography-mass spectrometry for the determination of several endocrine disruptor compounds in environmental water samples

The analysis of organic pollutants in environmental water samples requires a pre-concentration step. Pre-concentration techniques such as stir bar sorptive extraction (SBSE) have gained popularity since they minimise the use of toxic organic solvents and can be considered as green analytical techniques. Similar to other pre-concentration techniques, one of the problems when SBSE is used is the matrix effect, which often occurs during the analysis of environmental water samples such as estuarine or wastewater samples. The present work studied the matrix effect during SBSE coupled to in-tube derivatisation–thermal desorption (TD)–gas chromatography–mass spectrometry for the determination of several endocrine disruptor compounds, such as alkylphenols, bisphenol A, estrogens and sterols, in environmental water samples, after optimisation of the major variables affecting the determination. Variables such as the addition of methanol or an inert salt to the donor phase, the extraction temperature, the volume of the donor phase, the stirring rate and the extraction time were studied during the SBSE optimisation. In the case of the in-tube derivatisation and TD step, the volume of the derivatisation reagent (N,O-bis(trimethylsilyl)triufloroacetamide with 1% of trimethylchlorosilane (BSTFA + 1% TMCS)) and the cryo-focusing temperature were fixed (2 μL and −50 °C, respectively) according to a consensus between maximum signal and optimal operation conditions. Good apparent recovery values (78–124%) were obtained for most of the analytes in Milli-Q water, except for 4-tert-octylphenol (4-tOP), which showed apparent recovery values exceeding 100%. Precision (n = 4) was in the 2–27%, and method detection limits were in the low nanogrammes per litre level for most of the analytes studied. The matrix effect was studied using two different approaches. On the one hand, Milli-Q water samples were spiked with humic acids, and apparent recovery values were studied with and without correction with the corresponding deuterated analogue. On the other hand, estuarine water and wastewater samples were spiked with known concentrations of target analytes, and apparent recoveries were studied as explained above. In general, the matrix effect could be corrected with the use of deuterated analogues, except for 4-tOP and nonylphenols for which [²H₄]-n-nonylphenol did not provide good corrections.