Determination of polybrominated diphenyl ethers at trace levels in environmental waters using hollow-fiber microporous membrane liquid–liquid extraction and gas chromatography–mass spectrometry

Hollow fibre supported liquid membrane extraction for BTEX metabolites analysis in human teeth as biomarkers

The use of human teeth as biomarkers has been previously applied to characterize environmental exposure mainly to metal contamination. Difficulties arise when the contaminants are volatile or its concentration level is very low. This study presents the development of a methodology based on the transport through hollow fibre membrane liquid-phase microextraction (HF-LPME), followed by HPLC-UV measurement, to determine three different metabolites of BTEX contaminants, mandelic acid (MA), hyppuric acid (HA), and methylhippuric acid (4mHA). The driving force for the liquid membrane has been studied by using both non-facilitated (pH gradient 2-12) and facilitated transport (ionic and non-ionic carriers). Enrichment factors of several hundreds were accomplished. Different ionic and non-ionic water insoluble compounds were used as metabolite carriers for the facilitated transport at HF-LPME. Three organic solvents were used to constitute the liquid membrane, dodecane, dihexyl ether and n-decanol. Other parameters affecting the extraction process, such as extraction time, stirring speed, acceptor buffer and salt content were optimised in spiked solutions and selected those that presented the best enrichment factors for all analytes. Final conditions were established for donor solution as 20mL, pH2 of 0.5M NaCl, the OLM (Organic Liquid Membrane) as n-decanol and the acceptor solution as 40μL of 1M NaOH. The selected extraction time was 20h with stirring speed of 500rpm. Validation of the optimised method included the determination of individual linearity range (MA: 0.002-5.7μg; HA: 0.01-7.9μg; 4mHA 0.002-5.3μg), limits of detection (MA: 1.6ng; HA: 0.2ng; 4mHA 0.2ng), repeatability (RSD 7-10%) and reproducibility (5-8%). The developed method was applied to the analysis of MA, HA and 4mHA in teeth samples of 8 workers exposed to BTEX.

DNA aptamers for selective identification and separation of flame retardant chemicals

Polybrominated diphenyl ethers (PBDEs) are group of chemicals which are representative persistent organic pollutants (POPs) and used as brominated flame retardants for many consumer products. PBDEs were phased out since 2009 but are still frequently observed in various environmental matrices and human body. Here, we report ssDNA aptamers which bind to BDE47, one of the PBDE congeners commonly found in various environmental matrices, and show affinity to other major tri-to hepta- BDE congeners. The PBDE specific aptamers were isolated from random library of ssDNA using Mag-SELEX. Two out of 15 sequences, based on their alignment and hairpin loop structures, were chosen to determine dissociation constant with BDE47 and showed from picomolar to nanomolar affinities (200 pM and 1.53 nM). The aptamers displayed high selectivity to the original target, BDE47, and implying general specificity to PBDE backbone with varying affinities to other congeners. Further, we showed that the use of two aptamers together could enhance the separation efficiency of BDE47 and other BDE congeners when dissolved in a solvent compared to use of single aptamer. These aptamers are expected to provide a tool for preliminary screening or quick separation of PBDEs in environmental samples prior to trace quantitative analysis.

Selective and Sensitive Sensing of Flame Retardant Chemicals Through Phage Display Discovered Recognition Peptide

We report a highly selective and sensitive biosensor for the detection of an environmentally toxic molecule, decabrominated diphenyl ether (DBDE), one of the most common congeners of the polybrominated frame retardants (polybrominated diphenyl ether (PBDE)), using newly discovered DBDE peptide receptors integrated with carbon nanotube field-effect transistors (CNT-FET). The specific DBDE peptide receptor was identified using a high-throughput screening process of phage library display. The resulting binding peptide carries an interesting consensus binding pocket with two Trp-His/Asn-Trp repeats, which binds to the DBDE in a multivalent manner. We integrated the novel DBDE binding peptide onto the CNT-FET using polydiacetylene coating materials linked through cysteine-maleimide click chemistry. The resulting biosensor could detect the desired DBDE selectively with a 1 fM detection limit. Our combined approaches of selective receptor discovery, material nanocoating through click chemistry, and integration onto a sensitive CNT-FET electronic sensor for desired target chemicals will pave the way toward the rapid development of portable and easy-to-use biosensors for desired chemicals to protect our health and environment.

A fluorescence-based method for rapid and direct determination of polybrominated diphenyl ethers in water

A new method was developed for rapid and direct measurement of polybrominated diphenyl ethers (PBDEs) in aqueous samples using fluorescence spectroscopy. The fluorescence spectra of tri- to deca-BDE (BDE 28, 47, 99, 153, 190, and 209) commonly found in environment were measured at variable emission and excitation wavelengths. The results revealed that the PBDEs have distinct fluorescence spectral profiles and peak positions that can be exploited to identify these species and determine their concentrations in aqueous solutions. The detection limits as determined in deionized water spiked with PBDEs are 1.71-5.82 ng/L for BDE 28, BDE 47, BDE 190, and BDE 209 and 45.55-69.95 ng/L for BDE 99 and BDE 153. The effects of environmental variables including pH, humic substance, and groundwater chemical composition on PBDEs measurements were also investigated. These environmental variables affected fluorescence intensity, but their effect can be corrected through linear additivity and separation of spectral signal contribution. Compared with conventional GC-based analytical methods, the fluorescence spectroscopy method is more efficient as it only uses a small amount of samples (2-4 mL), avoids lengthy complicated concentration and extraction steps, and has a low detection limit of a few ng/L.

Identification of two novel brominated contaminants in water samples by ultra-high performance liquid chromatography-Orbitrap Fusion Tribrid mass spectrometer

Tetrabromobisphenol A mono(2-hydroxyethyl ether) (TBBPA-MHEE) and TBBPA mono(glycidyl ether) (TBBPA-MGE), two impurities of TBBPA derivatives, were hypothesized to be novel brominated contaminants with potential toxicity. However, due to lacking of analytical method and pure standards, their environmental behavior and toxicity have not been studied. Herein we developed a sensitive method based on ultra-high performance liquid chromatography-Orbitrap Fusion Tribrid mass spectrometer (UHPLC-Orbitrap Fusion TMS) for simultaneous detection of TBBPA-MHEE and TBBPA-MGE in water samples. The sample pretreatment method and the experimental conditions of UHPLC and Orbitrap Fusion TMS, were optimized in detail. The instrument detection limits (IDLs) for TBBPA-MHEE and TBBPA-MGE were 0.5pg and 0.6pg, respectively. The method detection limits (MDLs) for TBBPA-MHEE and TBBPA-MGE in river water samples were 0.9 and 0.8ng/L. With the proposed method, we were able to detect TBBPA-MHEE and TBBPA-MGE for the first time in water samples and technical products of TBBPA derivatives. Therefore, UHPLC-Orbitrap Fusion TMS is a simple and effective tool for identification and quantification of novel contaminants in the environment.

Plunger-in-needle solid-phase microextraction with graphene-based sol-gel coating as sorbent for determination of polybrominated diphenyl ethers

A solid-phase microextraction (SPME) device, assembled with a commercially available plunger-in-needle microsyringe, with the plunger coated with graphene via a sol-gel approach, was developed for the gas chromatographic-mass spectrometric determination of polybrominated diphenyl ethers (PBDEs) in environmental samples. This is the first application of graphene-based sol-gel coating as SPME sorbent. Parameters affecting the extraction efficiency were investigated in detail. The new coating exhibited enrichment factors for PBDEs between 1378 and 2859. The unique planar structure of graphene enhanced the π-π interaction with the aromatic PBDEs; additionally, the sol-gel coating technique created a porous three-dimensional network structure which offered larger surface area for extraction. The stainless steel plunger provided firm support for the coating and enhanced the durability of the assembly. The plunger-in-needle microsyringe represents a ready-made tool for SPME implementation. Under the optimized conditions, the method detection limits for five PBDEs were in the range of 0.2 and 5.3 ng/L (at a signal/noise ratio of 3) and the precision (% relative standard deviation, n=5) was 3.2-5.0% at a concentration level of 100 ng/L. The linearities were 5-1000 or 10-1000 ng/L for different PBDEs. Finally, the proposed method was successfully applied to the extraction and determination by gas chromatography-mass spectrometry of PBDEs in canal water samples.

Application of ACD/LABS 12 program for determination of conditions for experimental membrane extraction of pesticides

This paper analyzes the conditions for membrane extraction of pesticides using ACD / LABS 12 program. The program contains a large database of more than 2000 compounds and their ionized species, for determining the pKa, further analysis includes 600 new compounds confirmed by Hammett?s equation, which gives more precise values for logD and solubility. The 16 pesticides of different classes (organophosphates, carbamates, carbamidas, neonicotinoids etc.) and polarities commonly used in Serbia were examined. The program is used to calculate logD, pKa and solubility at different pH values for the mixture of pesticides. Based on the calculated values, the conditions for the extraction of pesticides in water using two-phase liquid-liquid membrane extraction were optimized.

Liquid-phase microextraction with porous hollow fibers, a miniaturized and highly flexible format for liquid–liquid extraction

Since 1999, substantial research has been devoted to the development of liquid-phase microextraction (LPME) based on porous hollow fibers. With this technology, target analytes are extracted from aqueous samples, through a thin supported liquid membrane (SLM) sustained in the pores in the wall of a porous hollow fiber, and further into a microL volume of acceptor solution placed inside the lumen of the hollow fiber. After extraction, the acceptor solution is directly subjected to a final chemical analysis by liquid chromatography (HPLC), gas chromatography (GC), capillary electrophoresis (CE), or mass spectrometry (MS). In this review, LPME will be discussed with focus on extraction principles, historical development, fundamental theory, and performance. Also, major applications have been compiled, and recent forefront developments will be discussed.