Solid phase microextraction Arrow for the determination of synthetic musk fragrances in fish samples.

A novel solid phase microextraction Arrow (SPME Arrow) system has been applied for the first time to determine synthetic musk fragrances in fish samples. The lack of regulation concerning the concentration of musk fragrances in fish along with the risk associated to these compounds has led to an increased development of analytical methods on this topic. This study applies SPME Arrow followed by gas chromatography coupled to tandem mass spectrometry (ion trap) to determine nine musk fragrances and compares this novel technique with its predecessor (SPME). Parameters such as type of coating, extraction time and temperature as well as water addition were optimized to achieve higher sensitivity. Results show that detection limits ranging between 0.5 ng g-1 (for cashmeran, celestolide, phantolide, tonalide and musk ketone) and 2.5 ng g-1 (dry weight) (for musk xylene) when SPME Arrow is used instead of a conventional fibre, with an up to ten-fold increase in sensitivity. Moreover, commercial fish samples were analysed using the method developed and galaxolideand tonalidewere quantified at concentrations ranging from 6.5 ng g-1 to 17.5 ng g-1 (d.w.) and 2.9 ng g-1 and 5.1 ng g-1 (d.w.) in all the species analysed.

Investigation of carbon-based nanomaterials as sorbents for headspace in-tube extraction of polycyclic aromatic hydrocarbons.

Carbon-based nanomaterials (CNM) represent promising materials for the application as sorbents in micro- and other extraction devices. In this work, we investigate the applicability of five different CNM (multi-walled carbon nanotubes (MWCNTs), fullerenes, carboxylic acid functionalized multi-walled carbon nanotubes (MWCNTs-COOH), graphene platelets, and carbon nanohorns) for their performance on PAH extraction from the aqueous phase by headspace in-tube extraction (HS-ITEX). Optimal extraction parameters for HS-ITEX were determined using a Box-Behnken experimental design. From the extraction yield response, central point analysis, fullerenes showed the best extraction properties for the eight selected headspace compatible PAHs (naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, and pyrene). Fullerenes were used for a further method validation including the linear range, limit of detection, precision, as well as recovery. Finally, extraction yields were compared to a commercial material (Tenax GR), demonstrating that fullerene represents a better option as sorbent in ITEX for PAH analysis. Method detection limits for the PAH on fullerene ranged from 10 to 300 ng L-1, with recoveries between 45 and 103%.

Sorbent material characterization using in-tube extraction needles as inverse gas chromatography column.

In-tube extraction is a full automated enrichment technique that consists of a stainless-steel needle, packed with sorbent material for the extraction of volatile and semivolatile compounds. In principle, all particulate sorbents used for enrichment in air or headspace analysis can be used. However, the selection of the sorbents is merely based on empirical considerations rather than on experimental data, which is caused by a lack of knowledge about the relevant physicochemical properties of the sorbent. Especially, the knowledge of hydrostatic, advective, diffusive, and dispersion mechanisms in addition to sorption enthalpies are important for combined transport and sorption models. To provide these missing parameters, we developed and evaluated a method in which an ordinary in-tube extraction needle was employed directly as column for sorbent characterization by inverse gas chromatography. As probe compounds, benzene, ethyl acetate, and 3-methyl-1-butanol were used to determine thermodynamic parameters such as sorption enthalpy, partitioning constant between the solid and gas phase, and kinetic parameters such as the diffusion coefficient, dispersion coefficient, and apparent permeability, exemplarily. As sorbent, three commercially available phases were characterized to demonstrate the applicability of the method.

Solid phase microextraction Arrow for the sampling of volatile amines in wastewater and atmosphere.

A new method is introduced for the sampling of volatile low molecular weight alkylamines in ambient air and wastewater by utilizing a novel SPME Arrow system, which contains a larger volume of sorbent compared to a standard SPME fiber. Parameters affecting the extraction, such as coating material, need for preconcentration, sample volume, pH, stirring rate, salt addition, extraction time and temperature were carefully optimized. In addition, analysis conditions, including desorption temperature and time as well as gas chromatographic parameters, were optimized. Compared to conventional SPME fiber, the SPME Arrow had better robustness and sensitivity. Average intermediate reproducibility of the method expressed as relative standard deviation was 12% for dimethylamine and 14% for trimethylamine, and their limit of quantification 10µg/L and 0.13µg/L respectively. Working range was from limits of quantification to 500µg/L for dimethylamine and to 130µg/L for trimethylamine. Several alkylamines were qualitatively analyzed in real samples, while target compounds dimethyl- and trimethylamines were quantified. The concentrations in influent and effluent wastewater samples were almost the same (∼80µg/L for dimethylamine, 120µg/L for trimethylamine) meaning that amines pass the water purification process unchanged or they are produced at the same rate as they are removed. For the air samples, preconcentration with phosphoric acid coated denuder was required and the concentration of trimethylamine was found to be around 1ng/m(3). The developed method was compared with optimized method based on conventional SPME and advantages and disadvantages of both approaches are discussed.

Optimization strategies of in-tube extraction (ITEX) methods.

Microextraction techniques, especially dynamic techniques like in-tube extraction (ITEX), can require an extensive method optimization procedure. This work summarizes the experiences from several methods and gives recommendations for the setting of proper extraction conditions to minimize experimental effort. Therefore, the governing parameters of the extraction and injection stages are discussed. This includes the relative extraction efficiencies of 11 kinds of sorbent tubes, either commercially available or custom made, regarding 53 analytes from different classes of compounds. They cover aromatics, heterocyclic aromatics, halogenated hydrocarbons, fuel oxygenates, alcohols, esters, and aldehydes. The number of extraction strokes and the corresponding extraction flow, also in dependence of the expected analyte concentrations, are discussed as well as the interactions between sample and extraction phase temperature. The injection parameters cover two different injection methods. The first is intended for the analysis of highly volatile analytes and the second either for the analysis of lower volatile analytes or when the analytes can be re-focused by a cold trap. The desorption volume, the desorption temperature, and the desorption flow are compared, together with the suitability of both methods for analytes of varying volatilities. The results are summarized in a flow chart, which can be used to select favorable starting conditions for further method optimization.

In-Tube Extraction-GC-MS as a High-Capacity Enrichment Technique for the Analysis of Alcoholic Beverages.

An in-tube extraction (ITEX) method for the GC-MS analysis of volatile constituents of alcoholic beverages was developed and applied in the analysis of 46 beers from six varieties, Alt, Helles, Kölsch, Pilsener beer, Schwarzbier, and wheat beer, which are popular in Germany. The extraction performance of nine different sorbent materials was evaluated. The best overall sensitivity was achieved using Tenax TA, with method detection limits down to 0.01 µg L-1, whereas the widest linear range was possible with PDMS, covering almost 5 orders of magnitude. This is the first application of PDMS in ITEX as a high-capacity extraction device and highlights the importance of choosing the appropriate sorbent material for the analytical task at hand. A satisfying chemometric discrimination of all analyzed beer varieties was possible, and alcohol-free beers could clearly be separated from regular beers, also.

Multi-walled carbon nanotubes as sorptive material for solventless in-tube microextraction (ITEX2)--a factorial design study.

Multi-walled carbon nanotubes were evaluated as sorptive packing material for in-tube microextraction (ITEX2) in combination with GC-MS for the analysis of benzene, toluene, ethylbenzene, xylenes, and naphthalene in aqueous samples. For method development, a three-level full factorial design of experiment (DoE) was performed incorporating extraction temperature, number of extraction strokes, and extraction flow. The statistical analysis of method development showed that all considered extraction parameters significantly affected the extraction yield. Furthermore, it was shown that some factors significantly interacted with each other, which indicates the advantage of using DoE for method development. The thereby optimized ITEX2 protocol was validated regarding its linear dynamic range, method detection limit (MDL), and precision. The MDLs of investigated analytes ranged between 2 ng L(-1) for naphthalene and 11 ng L(-1) for p-xylene. The relatively low MDL obtained for naphthalene, despite its comparably low air-water partitioning, can be explained by its strong interaction with carbon nanotubes. All obtained MDLs are at least comparable to previous reports on microextraction techniques, emphasizing both the quality of ITEX2 and the highly promising sorbent characteristics of carbon nanotubes. Furthermore, the method was applied to three real samples, which demonstrated good recoveries of analytes from tap water, a bank filtrate, and an effluent from a wastewater treatment plant.

In-tube extraction of volatile organic compounds from aqueous samples: an economical alternative to purge and trap enrichment.

A novel in-tube extraction device (ITEX 2) for headspace sampling was evaluated for GC/MS analysis of aqueous samples. Twenty compounds of regulatory and drinking water quality importance were analyzed, including halogenated hydrocarbons, BTEX compounds (benzene, toluene, ethylbenzene, xylenes), fuel oxygenates, geosmin, and 2-methylisoborneol. Five commercially available sorbent traps were compared for their compound specific extraction yield. On the basis of the results, a mixed bed trap was prepared and evaluated. The extraction parameters were optimized to yield maximum sensitivity within the time of a GC run, to avoid unnecessary downtime of the system. Method detection limits of 1-10 ng L(-1) were achieved for volatile organic compounds (VOCs), which is much lower than demands by regulatory limit values. The performance of the ITEX system is similar to that of purge and trap systems, but it requires lower sample volumes and is less prone to contamination, much simpler, more flexible, and affordable. Average relative standard deviations below 10% were achieved for all analytes, and recoveries from spiked tap water samples were between 90% and 103%, mostly. The extraction is nonexhaustive, removing a fraction of 7% to 55% of the target compounds, depending on the air-water partitioning coefficients. The method was also tested with nonsynthetic samples, including tap, pond, and reservoir water and different soft drinks.

In-tube extraction for enrichment of volatile organic hydrocarbons from aqueous samples.

In-tube extraction (ITEX) is a novel solventless extraction technique in which a headspace syringe with a needle body filled with a sorbent (here: Tenax TA) is used. The analytes are extracted from sample headspace by dynamic extraction. The needle body is surrounded by a separate heater, which is used for thermal desorption of analytes into the injection port of a GC system. We report here for the first time the optimization and evaluation of a fully automated analytical method based on ITEX. As target analytes, 19 common groundwater contaminants such as halogenated volatiles and monoaromatic compounds have been chosen. Method related parameters such as extraction temperature, number of extraction cycles, extraction and desorption volume as well as extraction and desorption flow rates were investigated in detail. The linear dynamic range of the ITEX method ranged over six orders of magnitude between 0.028 microg/L and 1218 microg/L with linear correlation coefficients between 0.990 and 0.998 for the investigated compounds. Method detection limits for monoaromatic compounds were between 28 ng/L (ethylbenzene) and 68 ng/L (1,2,4-trimethylbenzene). For halogenated volatile organic compounds, method detection limits between 48 ng/L (chloroform) and 799 ng/L (dichloromethane) were obtained. The precision of the method with external calibration was between 3.1% (chloroform ethylbenzene) and 7.4% (1,2,3-trimethylbenzene).