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.     

Multiresidue screening of endocrine-disrupting chemicals and pharmaceuticals in aqueous samples by multi-stir bar sorptive extraction–single desorption–capillary gas chromatography/mass spectrometry

A multiresidue method for screening endocrine-disrupting chemicals (EDCs) and pharmaceuticals in aqueous samples is presented. Four 10-mL aliquots of water were taken for stir bar sorptive extraction (SBSE) and they were treated in the following way. In sample one, in situ derivatization was performed with acetic acid anhydride to improve the extraction efficiencies and chromatographic analysis of phenolic compounds. For the same reasons, aliquot two was treated with ethyl chloroformate to improve amine and acid extraction and analysis, and aliquot three with tetraethylborate to enhance organotin compound extraction and analysis. Methanol was added to sample four to stop adsorption of apolar solutes on the wall. After SBSE, the four stir bars, together with a plug of glass wool impregnated with bis(trimethylylsilyl)trifluoroacetamide (BSTFA) to derivatize hydroxyl functionalities, were introduced into the same thermal desorption tube, heat-desorbed, and analyzed simultaneously by capillary GC/MS. The figures of merit of the method were evaluated with an EDC model mixture. In scan-mode MS, the limits of detection (LODs) were in the range 1–500 ng/L, while the LODs dropped by a factor of 50–100 when ion monitoring MS was applied to the targets. The performance of the method was illustrated by analysing some real-world water samples.     

Determination of pesticides in seaweeds by pressurized liquid extraction and programmed temperature vaporization-based large volume injection–gas chromatography–tandem mass spectrometry

A rapid method for the simultaneous identification and quantification of pesticide residues in edible seaweed has been developed. Target analytes were three pyrethroid, a carbamate and two organophosphorus pesticides. The procedure consists of a pressurized liquid extraction (PLE) with integrated clean-up, followed by gas chromatography coupled to tandem mass spectrometry. Five PLE parameters were investigated using a screening design: temperature, static extraction time, number of cycles, percent of flush volume and quantitative composition of the n-hexane/ethyl acetate extraction solvent. The effect of the in-cell clean-up with Florisil^® and graphitized carbon black adsorbents was investigated using a Doehlert response surface design. Large volumes of sample extracts were injected using a programmed-temperature vaporizer (PTV-LVI) to improve both sensitivity and selectivity of measurements. Quantification was carried by the internal standard method with surrogate deuterated standards. The method showed excellent linearity (R² > 0.999) and precision (relative standard deviation, RSD ≤ 8%) for all compounds, with detection limits ranging from 0.3 pg g⁻¹ for chlorpyrifos-ethyl, to 3.0 pg g⁻¹ for carbaryl (23.1 pg g⁻¹ for deltamethrin). Recoveries in real seaweed samples were within the range 82–108%. The method was satisfactory validated for the analysis of wild and cultivated edible seaweeds. The presence of pyrethroid and organophosphorus pesticides in some of the samples was evidenced.     

Determination of endocrine-disrupting chemicals in the liquid and solid phases of activated sludge by solid phase extraction and gas chromatography–mass spectrometry

The highly complex matrix of activated sludge in sewage treatment plants (STPs) makes it difficult to detect endocrine-disrupting chemicals (EDCs) which are usually present at low concentration levels. To date, no literature has reported the concentrations of steroid estrogens in activated sludge in China and very limited data are available worldwide. In this work, a highly selective and sensitive analytical method was developed for simultaneous determination of two classes of EDCs, including estrone (E1), 17β-estradiol (E2), estriol (E3), 17α-ethynylestradiol (EE2), 4-nonylphenol (NP) and bisphenol A (BPA), in the liquid and solid phases of activated sludge. The procedures for sample preparation, extracts derivatization, and gas chromatography–mass spectrometry (GC–MS) quantification were all optimized to effectively determine target EDCs while minimizing matrix interference. The developed method showed good calibration linearity, recovery, precision, and a low limit of quantification (LOQ) for all selected EDCs in both liquid and solid phases of activated sludge. It was successfully applied to determine the concentrations of EDCs in activated sludge samples from two STPs located in Beijing and Shanghai of China, respectively.     

Full automation of solid-phase microextraction/on-fiber derivatization for simultaneous determination of endocrine-disrupting chemicals and steroid hormones by gas chromatography–mass spectrometry

A fully automated method using direct immersion solid-phase microextraction (DI-SPME) and headspace on-fiber silylation for simultaneous determinations of exogenous endocrine-disrupting chemicals (EDCs) and endogenous steroid hormones in environmental aqueous and biological samples by gas chromatography–mass spectrometry (GC-MS) was developed and compared to a previously reported manual method. Three EDCs and five endocrine steroid hormones were selected to evaluate this method. The extraction and derivatization time, ion strength, pH, incubation temperature, sample volume, and extraction solvent were optimized. Satisfactory results in pure water were obtained in terms of linearity of calibration curve (R ²=0.9932–1.0000), dynamic range (3 orders of magnitude), precision (4–9% RSD), as well as LOD (0.001–0.124 μg L⁻¹) and LOQ (0.004–0.413 μg L⁻¹), respectively. These results were similar to those obtained using a manual method, and moreover, the precision was improved. This new automated method has been applied to the determinations of target compounds in real samples used in our previous study on a manual SPME method. Exogenous octylphenol (OP), technical grade nonylphenol (t-NP), and diethylstilbestrol (DES) were at 0.13, 5.03, and 0.02 μg L⁻¹ in river water and 3.76, 13.25, and 0.10 μg L⁻¹ in fish serum, respectively. Natural steroid hormones estrone (E₁), 17β-estradiol (E₂), and testosterone (T) were at 0.19, 0.11, and 6.22 μg L⁻¹ in river water; and in female fish serum E₁, E₂, and pregnenolone (PREG) were at 1.37, 1.95, and 6.25 μg L⁻¹, respectively. These results were confirmed by the manual method. The developed fully automated SPME and on-fiber silylation procedures showed satisfactory applications in environmental analysis and the performances show improved precision and a reduced analysis time compared to the manual method.     

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.     

Stir-bar-sorptive extraction and liquid desorption combined with large-volume injection gas chromatography–mass spectrometry for ultra-trace analysis of musk compounds in environmental water matrices

Stir-bar-sorptive extraction with liquid desorption followed by large-volume injection and capillary gas chromatography coupled to mass spectrometry in selected ion monitoring acquisition mode (SBSE–LD/LVI-GC–MS(SIM)) has been developed to monitor ultra-traces of four musks (celestolide (ADBI), galaxolide (HHCB), tonalide (AHTN) and musk ketone (MK)) in environmental water matrices. Instrumental calibration (LVI-GC–MS(SIM)) and experimental conditions that could affect the SBSE-LD efficiency are discussed. Assays performed on 30-mL water samples spiked at 200 ng L^?1 under optimized experimental conditions yielded recoveries ranging from 83.7?±?8.1% (MK) to 107.6?±?10.8% (HHCB). Furthermore, the experimental data were in very good agreement with predicted theoretical equilibria described by octanol–water partition coefficients (K _PDMS/W?≈?K _O/W). The methodology also showed excellent linear dynamic ranges for the four musks studied, with correlation coefficients higher than 0.9961, limits of detection and quantification between 12 and 19 ng L^?1 and between 41 and 62 ng L^?1, respectively, and suitable precision (< 20%). Application of this method for analysis of the musks in real water matrices such as tap, river, sea, and urban wastewater samples resulted in convenient selectivity, high sensitivity and accuracy using the standard addition methodology. The proposed method (SBSE–LD/LVI-GC–MS(SIM)) was shown to be feasible and sensitive, with a low-sample volume requirement, for determination of musk compounds in environmental water matrices at the ultra-trace level, overcoming several disadvantages presented by other sample-preparation techniques.     

Determination of organic priority pollutants in the low nanogram-per-litre range in water by solid-phase extraction disk combined with large-volume injection/gas chromatography–mass spectrometry

Polybrominated diphenyl ethers, polychlorinated biphenyls, polycyclic aromatic hydrocarbons and organochlorine pesticides in the low nanogram-per-litre range in water were enriched by solid-phase extraction (SPE) disks and their concentration determined by large-volume injection/gas chromatography–mass spectrometry (LVI/GC-MS). One advantage of using SPE disks in comparison with SPE cartridges is that suspended particulate matter (SPM) does not have to be separated prior to the enrichment step, which saves time and effort. To increase the sensitivity of the method, the SPE disk procedure was combined with LVI/GC-MS, which has not been reported so far for water analysis. The method was calibrated in ranges from 0.25 to 2.5 ng/L and from 2.5 to 25 ng/L. The average recovery was 76 % at an analyte concentration of 2.5 ng/L. The limits of quantification, defined at a signal-to-noise ratio of 6:1, reach from 0.1 to 24.0 ng/L and are up to 400 times lower than previously reported in water analysis. By the developed SPE/LVI/GC-MS method, it is possible to investigate the whole water sample without prior separation of the SPM within 2 h including GC-MS analysis.     

Large volume injection of water in gas chromatography–mass spectrometry using the Through Oven Transfer Adsorption Desorption interface: Application to multiresidue analysis of pesticides

In the present work, the potential of the Through Oven Transfer Adsorption Desorption (TOTAD) interface for the large volume injection (LVI) of aqueous samples in gas chromatography (GC) using a mass spectrometry (MS) detector is demonstrated. To this end, a new method for the determination of pesticides in water is presented, being the first developed method in which injection of large amounts of polar solvents using the TOTAD interface and an MS detector are combined, is applied to the determination of pesticides in water. Water samples, as large as 5 ml, were directly injected into a capillary GC. No sample pre-treatment step other than simple filtration was needed. The TOTAD interface allows the introduction of several millilitres of water, while maintaining good chromatographic characteristics. The water is almost entirely eliminated, so that LVI of aqueous samples and an MS detector can be used without problems. Organophosphorus, organochlorine, and triazine pesticides were determined in one run. Calibration curves were linear in the range tested and the sensitivity achieved injecting 5 ml of water sample was sufficient for most of the target pesticides but not for all of them. Sensitivity of the analysis can be improved by increasing the sample volume. No variability was observed in the retention times and relative standard deviations from absolute peak areas were good, considering that they corresponded to the overall analysis. The method was applied to the analysis of pesticide residues in real water samples.     

Application of dynamic liquid-phase microextraction and injection port derivatization combined with gas chromatography–mass spectrometry to the determination of acidic pharmaceutically active compounds in water samples

A method has been established for the determination of four pharmaceutically active compounds (ibuprofen, ketoprofen, naproxen and clofibric acid) in water samples using dynamic hollow fiber liquid-phase microextraction (HF/LPME) followed by gas chromatography (GC) injection port derivatization and GC–mass spectrometric (MS) determination. Dynamic HF/LPME is a novel approach to microextraction that involves the use of a programmable syringe pump to move the liquid phases participating in the extraction so as to facilitate the process. Trimethylanilinium hydroxide (TMAH) was used as derivatization reagent for the analytes to increase their volatility and improve chromatographic separation. Parameters that affect extraction efficiency (selection of organic solvent, volume of organic solvent, agitation in the donor phase, plunger movement and extraction time) were investigated. Under optimal conditions, the proposed method provided good enrichment factors up to 251, reproducibility ranging from 3.26% to 10.61%, and good linearity from 0.2 to 50 μg/L. The limits of detection ranged between 0.01 and 0.05 μg/L (S/N = 3) using selective ion monitoring. This method was applied to the determination of the four pharmaceutically active compounds in tap water and wastewater collected from a drain in the vicinity of a hospital.     

Determination of tributyltin (TBT) in marine sediment using pressurised liquid extraction–gas chromatography–isotope dilution mass spectrometry (PLE–GC–IDMS) with a hexane–tropolone mixture

Extraction conditions for the determination of tributyltin (TBT) in sediment samples have been developed further. The analytical procedure is based on spiking with isotopically labelled analyte, pressurised liquid extraction (PLE) with a hexane/tropolone mixture, Grignard derivatization and quantification by GC–MS. It was applied to two unknown sediment samples as part of an intercomparison exercise of the Comité Consultatif pour la Quantité de Matière (CCQM). The detection limit was approximately 1.5 ng/g TBT as Sn, while the repeatability and intermediate precision (as the coefficient of variation) were 1.9% and 3.2%, respectively. The expanded uncertainty was 6.2% (coverage factor k = 2), and the accuracy was confirmed by measurement of a certified reference material.     

Determination of organic priority pollutants and emerging compounds in wastewater and snow samples using multiresidue protocols on the basis of microextraction by packed sorbents coupled to large volume injection gas chromatography–mass spectrometry analysis

This paper describes the development and validation of a new procedure for the simultaneous determination of 41 multi-class priority and emerging organic pollutants in water samples using microextraction by packed sorbent (MEPS) followed by large volume injection–gas chromatography–mass spectrometry (LVI–GC–MS). Apart from method parameter optimization the influence of humic acids as matrix components on the extraction efficiency of MEPS procedure was also evaluated. The list of target compounds includes polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), phthalate esters (PEs), nonylphenols (NPs), bisphenol A (BPA) and selected steroid hormones. The performance of the new at-line microextraction-LVI–GC–MS protocol was compared to standard solid-phase extraction (SPE) and LVI–GC–MS analysis. LODs for 100 mL samples (SPE) ranged from 0.2 to 736 ng L⁻¹ were obtained. LODs for 800 μL of sample (MEPS) were between 0.2 and 266 ng L⁻¹. In the case of MEPS methodology even a sample volume of only 800 μL allowed to detect the target compounds. These results demonstrate the high sensitivity of both procedures which permitted to obtain good recoveries (>75%) for all cases. The precision of the methods, calculated as relative standard deviation (RSD) was below 21% for all compounds and both methodologies. Finally, the developed methods were applied to the determination of target analytes in various samples, including snow and wastewater.     

Microwave-assisted extraction (MAE) combined with gas chromatography–mass spectrometry (GC–MS) for determination of volatile small molecules to evaluate compatibility of antimicrobial peptide PL-5 spray with packaging materials

A simple and efficient method involving microwave-assisted extraction (MAE) combined with GC–MS was established to determine 1,3-di-tert-butylbenzene (DBB), 2,4-di-tert-butylphenol (DBP), 3,5-di-tert-butyl-4-hydroxybenzaldehyde (DBHBA) for evaluating the compatibility of antimicrobial peptide PL-5 spray with drug-packaging materials. In this study, the antimicrobial peptide PL-5 spray was purified using a Welchrom C18 column, and the high-density polyethylene spray bottle with liquid collection tube was first mixed with absolute ethanol, which would be subjected to MAE for further measurement by GC–MS. Various experimental parameters were systematically optimized, and good linearities were obtained within the range of 0.05–1.00 μg/mL for DBB and DBHBA and 0.50–10.00 μg/mL for DBP, with limits of detection (LODs) of 0.99 ng/mL (DBB), 16.34 ng/mL (DBP), and 1.64 ng/mL (DBHBA). Satisfactory recoveries that ranged from 96.0% to 107.2% were acquired, and the relative standard deviation was ≤ 4.7%. The results showed that the maximum daily usage of DBB, DBP, and DBHBA was 9.859, 163.445, and 16.399 ng, respectively, which was far below the corresponding permitted daily exposure values according to the safety assessment, indicating that the migration of analytes did not bring any potential safety risk. The compatibility between the drug and the packaging materials was favorable.