An electropolymerized aniline-based fiber coating for solid phase microextraction of phenols from water

Analysis of chloro- and nitrobenzenes in water by a simple polyaniline-based solid-phase microextraction coupled with gas chromatography

A simple solid-phase microextraction (SPME) device, coupled with gas chromatography-electron capture detection (GC-ECD) was developed to detect trace levels of chloro- and nitrobenzene compounds in environmental water samples. Polyaniline (PANI) was chosen as the extraction material for the SPME device, and was electrochemically deposited on a stainless steel wire to achieve high mechanical stability. Due to the peculiar pi-pi conjugated structure, PANI coating shows a stable performance in high temperature (to 350 degrees C) and solvents (organic and inorganic). The porous structure of PANI film characterized by scanning electron microscopy (SEM) revealed high extraction efficiency. The possible extraction mechanism was explained by the study carried out using electrochemical impedance spectroscopy (EIS). Eight chloro- and nitrobenzene compounds were selected to evaluate the SPME-GC procedures. The key parameters such as extraction and desorption temperature and time, and the ionic strength were investigated and optimized. The method was applied to the detection of environmental water samples collected from Taihu Lake, representing nowadays contamination level under industrial impact. The whole PANI-SPME-GC method offers high accuracy and precision, high sensitivity and low detection limits. Thus, the method developed could be used as a new way to monitor the trace levels of chloro- and nitrobenzene compounds in real water bodies.

In-capillary solid-phase extraction-capillary electrophoresis for the determination of chlorophenols in water

A novel CE method combined with SPE in a single capillary was developed for analysis of chlorophenols in water. A frit of 0.5 mm was first made by a sol-gel method, followed by packing a SPE sorbent in the inlet end of the capillary. Two phenol derivatives, 2,4-dichlorophenol and 2,4,5-trichlorophenol, were used as the model compounds. By loading sample solutions into the capillary, the two chlorophenols were extracted into the sorbent. They were desorbed by injecting only about 4 nL of methanol. Finally, the analytes were separated by conventional CE. The technique provided a concentration enhancement factor of over 4000-fold for both chlorophenols. The detection limits (S/N = 3) of 2,4-dichlorophenol and 2,4,5-trichlorophenol were determined to be 0.1 ng/mL and 0.07 ng/mL, respectively. For replicate analyses of 5 ng/mL of 2,4-dichlorophenol, within-day and between-day RSDs of migration time, peak height and peak area were in the range of 1.8-2.0%, 4.0-4.4% and 4.1-4.6%, respectively. The method shows wide linear range, acceptable reproducibility and excellent sensitivity, and it was applied to the analyses of spiked river water samples. The capillary packed with the SPE sorbents can be used for more than 400 runs without performance deterioration.

Multiwalled carbon nanotubes coated fibers for solid-phase microextraction of polybrominated diphenyl ethers in water and milk samples before gas chromatography with electron-capture detection

Determination of polybrominated diphenyl ethers (PBDEs) in environmental samples has raised great concerns due to the widespread use of PBDEs and their potential risk to humans. Solid-phase microextraction (SPME) is a fast, simple, cost-effective, and green sample preparation technique and is widely used for environmental analysis, but reports on the application of SPME for determination of PBDEs are very limited, and only a few publications dealing with commercial SPME fibers are available for extraction of PBDEs. Herein, we report a novel SPME method using multiwalled carbon nanotubes (MWCNTs) as the SPME fiber coating for gas chromatography with electron-capture detection (GC-ECD) of PBDEs in environmental samples. The MWCNTs coating gave much higher enhancement factors (616-1756) than poly (5% dibenzene-95% dimethylsiloxane) coating (139-384) and activated carbon coating (193-423). Thirty-minute extraction of 10 mL of sample solution using the MWCNTs coated fiber for GC-ECD determination yielded the limits of detection of 3.6-8.6 ng L(-1) and exhibited good linearity of the calibration functions (r(2)>0.995). The precision (RSD%, n=4) for peak area and retention time at the 500 ng L(-1) level was 6.9-8.8% and 0.6-0.9%, respectively. The developed method was successfully applied for the analysis of real samples including local river water, wastewater, and milk samples. The recovery of the PBDEs at 500 ng L(-1) spiked in these samples ranged from 90 to 119%. No PBDEs were detected in the river water and skimmed milk samples, whereas in the wastewater sample, 134-215 ng L(-1) of PBDEs were found. The PBDEs were detected in all whole fat milk samples, ranging from 13 to 484 ng L(-1). In a semiskimmed milk sample, only BDE-47 was found at 21 ng L(-1).

Determination of phthalates in water samples using polyaniline-based solid-phase microextraction coupled with gas chromatography

A simple solid-phase microextraction (SPME) device, coupled with gas chromatography-flame ionization detection (GC-FID), was developed to detect trace levels of phthalates in environmental water samples. Polyaniline (PANI) was chosen as the sorbent for the SPME device and was electrochemically deposited on a stainless steel wire to achieve high thermal and mechanical stability. The porous structure of the PANI film, characterized by scanning electron microscopy (SEM), suggested large extraction capability. Key parameters were optimized and five phthalates were selected to evaluate the SPME-GC procedures. The method was also applied to the analysis of lake and river water samples. Control experiments were carried out using commercial polyacrylate (PA) fiber. The new PANI-SPME-GC method offers high accuracy, precision and sensitivity and low detection limits. Thus, the method developed could be used as a new way to monitor the trace levels of phthalates in water medium. A possible extraction mechanism was investigated using electrochemical impedance spectroscopy (EIS).

Evaluation of solid-phase microextraction conditions for the determination of chlorophenols in honey samples using gas chromatography

A rapid and solvent-free method for the determination of nine chlorophenol (CP) compounds in honey samples using headspace solid-phase microextraction (HS-SPME) and gas chromatography with atomic emission detection (GC-AED) is developed. The different factors affecting the efficiency of the extraction and derivatization steps were carefully optimized. The polydimethylsiloxane-divinylbenzene (PDMS/DVB) fiber was the most suitable for preconcentrating the analytes from the headspace of an aqueous solution containing the dissolved honey samples where the chlorophenols had been submitted to acetylation. When the matrix effect was evaluated for different samples, it was concluded that standard addition calibration was required for quantification purposes. Detection limits roughly ranged from 0.1 to 2.4 ng g(-1), depending on the compound and the honey sample analyzed, with a fiber time exposure of only 15 min at 75 degrees C. The optimized method was successfully applied to different samples, some of the studied chlorophenols being detected in some of the analyzed honeys at concentration levels 0.6-9.4 ng g(-1).

Silicone glue coated stainless steel wire for solid phase microextraction

A new solid phase microextraction (SPME) fiber based on high-temperature silicone glue coated on a stainless steel wire is presented. The fiber coating can be prepared easily in a few minutes, it is mechanically stable and exhibits relatively high thermal stability (up to 260 degrees C). The extraction properties of the fiber to benzene, toluene, ethylbenzene, and xylenes (BTEX) were examined using both direct and headspace SPME modes coupled to gas chromatography-flame ionization detection. The effects of the extraction and desorption parameters including extraction and desorption time, sampling and desorption temperature, and ionic strength on the extraction/desorption efficiency have been studied. For both headspace and direct SPME the calibration graphs were linear in the concentration range from 0.5 microg L(-1) to 10 mg L(-1) (R2>0.996) and detection limits ranged from 0.07 to 0.24 microg L(-1). Single fiber repeatability and fiber-to-fiber reproducibility were less than 6.8 and 21.5%, respectively. Finally, headspace SPME was applied to determine BTEX in petrol station waste waters with spiked recoveries in the range of 89.7-105.2%.

SPME in environmental analysis

Recent advances in the use of solid-phase microextraction (SPME) in environmental analysis, including fiber coatings, derivatization techniques, and in-tube SPME, are reviewed in this article. Several calibration methods for SPME, including traditional calibration methods, the equilibrium extraction method, the exhaustive extraction method, and several diffusion-based calibration methods, are presented. Recent developed SPME devices for on-site sampling and several applications of SPME in environmental analysis are also introduced.

Strategies for the microextraction of polar organic contaminants in water samples

In this paper the most recent developments in the microextraction of polar analytes from aqueous environmental samples are critically reviewed. The particularities of different microextraction approaches, mainly solid-phase microextraction (SPME), stir-bar-sorptive extraction (SBSE), and liquid-phase microextraction (LPME), and their suitability for use in combination with chromatographic or electrically driven separation techniques for determination of polar species are discussed. The compatibility of microextraction techniques, especially SPME, with different derivatisation strategies enabling GC determination of polar analytes and improving their extractability is revised. In addition to the use of derivatisation reactions, the possibility of enhancing the yield of solid-phase microextraction methods for polar analytes by using new coatings and/or larger amounts of sorbent is also considered. Finally, attention is also focussed on describing the versatility of LPME in its different possible formats and its ability to improve selectivity in the extraction of polar analytes with acid-base properties by using separation membranes and buffer solutions, instead of organic solvents, as the acceptor solution.

Recent developments in solid-phase microextraction coatings and related techniques

During the last decade, solid-phase microextraction (SPME) has gained widespread acceptance for analyte matrix separation and preconcentration. Relatively few data are currently available dealing with in-house production of fibres with tailor-made properties to be used for SPME, though recently the number of publications evaluating new coatings has been considerably growing. This review, centred on publications that appeared during the last five years, is resuming different approaches which can be used for fibre production and further summarises alternative techniques closely related to SPME, such as in-tube extraction or single-drop microextraction (SDME). The aim is to give the reader a concise overview of recent developments in new coating procedures and materials, including the respective applications.

Determination of phenols in water samples by single-drop microextraction followed by in-syringe derivatization and gas chromatography–mass spectrometric detection

Trace analysis of phenolic compounds in water was performed by coupling single-drop microextraction (SDME) with in-syringe derivatization of the analytes and GC-MS analysis. The analytes were extracted from a 3ml sample solution using 2.5microl of hexyl acetate. After extraction, derivatization was carried out in syringe barrel using 0.5microl of N,O-bis(trimethylsilyl)acetamide. The influence of derivatizing reagent volume, derivatization time and temperature on the yield of the in-syringe silylation was investigated. Derivatization reaction is completed in 5min at 50 degrees C. Experimental SDME parameters, such as selection of organic solvent, sample pH, addition of salt, extraction time and temperature of extraction were studied. Analytical parameters, such as enrichment factor, precision, linearity and detection limits were also determined. The limits of detection were in the range of 4-61ng/l (S/N=3). The relative standard deviations obtained were between 4.8 and 12% (n=5).

Electrochemical preparation of composite polyaniline coating and its application in the determination of bisphenol A, 4-n-nonylphenol, 4-tert-octylphenol using direct solid phase microextraction coupled with high performance liquid chromatography

For SPME-HPLC, metal wires with better mechanical strength are preferred over the fused silica fibers. In this article, a novel composite polyaniline (CPANI) doped with PEG and polydimethylsiloxane coating (CPANI fiber) was prepared on a stainless steel wire by a three-electrode system: the fiber was used as the work electrode, a calomel electrode and a platinum electrode were used as the reference and the counter electrodes, respectively. To evaluate the new CPANI coating, the coating was used to extract three kinds of phenols (bisphenol A, 4-n-nonylphenol, and 4-tert-octylphenol) in water samples by direct-SPME mode and then desorbed in commercial SPME-HPLC interface to separation. The extraction procedure was also optimized. Five real water samples were investigated. Good recoveries were gained when environmental samples were analyzed.