Method development for the determination of wood preservatives in commercially treated wood using gas chromatography-mass spectrometry.

Fungicides and insecticides are commonly used preservatives to protect wood products against microbiological degradations. Currently, there is a lack of analytical methods addressing the quantitative determination of a wide range of wood preserving species in wood matrices. In this study, a reliable method was developed for the determination of a mixture of wood preserving agents with differing chemical structures (i.e., properties), including tebuconazole (TAZ), propiconazole (PAZ), 3-iodo-2-propynyl butylcarbamate (IPBC), and permethrin (PER), in pine wood. The analyte recoveries obtained by Soxhlet and multiple-stage sonication extractions were compared. While both extraction methods yielded similar results (80-100%), Soxhlet extraction was found to be less labor-intensive and thus preferred providing also lower RSDs of 1-6%. In comparison to methanol, commonly used as an extraction solvent for triazoles, acetone yielded similar extraction efficiencies for all analytes while reducing the time of sample concentration. The solid phase extraction method for triazoles was adapted to allow for a separation of IPBC and PER from the wood matrix. As opposed to previous studies, three recovery standards were employed, which enabled the correction of individual analyte losses during the sample preparation. The matrix-affected limits of detection (LODs) using gas chromatography with mass spectrometric detection were nearly the same for triazoles 0.07 and 0.21 ng g(-1) for PAZ and TAZ in sapwood and 0.18 and 0.21 ng g(-1) in heartwood, respectively. Higher LODs were observed for IPBC and PER: 3.9 and 1.7 ng g(-1) in sapwood, and 2.0 and 6.0 ng g(-1) in heartwood, respectively. The recoveries in the wood submitted to commercial sample treatment showed gradient distribution of analytes depending on the penetration of the treatment.

Study of desorption kinetics of polycyclic aromatic hydrocarbons (PAHs) from solid matrices using internally cooled coated fiber.

The kinetics of desorption of hydrophobic organic compounds (HOCs) from soil and sediment particles is important both from environmental and analytical chemistry points of view. Reliable techniques are required for prediction of desorption behaviour of HOCs from contaminated soils and sediments. In this study internally cooled coated fiber device, in which a PDMS hollow fiber extraction phase is cooled with liquid CO(2), was used as an exhaustive extraction sorbent phase for extraction of desorbed organic compounds (e.g. polycyclic aromatic hydrocarbons, PAHs) from both laboratory-spiked and naturally contaminated solid sample into the gaseous headspace in a batch system. The extraction time profiles were obtained at two different elevated temperatures (above 100 degrees C) for spiked sand and silica gel matrices. The slow desorption rate constants at each temperature were determined from desorption plots and the apparent activation energies of desorption were obtained from Arrhenius equations. The apparent activation energies of desorption of naphthalene, acenaphthylene and acenaphthene, from spiked silica gel, were approximately 60kJmol(-1), and were higher, 70 and 100kJmol(-1) for fluoranthene and anthracene, respectively. The fast and slow desorption rates and apparent activation energies of desorption for PAHs were obtained by spiking a naturally contaminated sediment sample with deuterated PAHs (PAHs-d(10)). The activation energies of native PAHs were higher than those of spiked deuterated PAHs, suggesting that the native compounds were more affected by retarded pore diffusion or slow mass transfer through glassy sorbent organic matter (SOM). The proposed technique in the present study is fully automated, and can extract the contaminants from the solid matrix fast and exhaustively, which makes it more time efficient and versatile compared to the commonly used technique for desorption studies, i.e. vial desorption.

Solid-phase microextraction under controlled agitation conditions for rapid on-site sampling of organic pollutants in water.

An electric drill coupled with a solid-phase microextraction (SPME) polydimethylsiloxane (PDMS) fiber or a PDMS thin film was used for rapid sampling of polycyclic aromatic hydrocarbons (PAHs) in aqueous samples. Laboratory experiments demonstrated that the sampling rates of SPME fiber and thin film can be predicted theoretically. Compared with the SPME fiber, the PDMS thin film active sampler exhibited a higher sampling rate and much better sensitivity due to its higher surface-to-volume ratio and its larger extraction phase volume. The amount of the analytes extracted by the thin film was around 100 times higher than those obtained by fiber, for both 5 min rapid sampling and equilibrium extraction. A new thin film active sampler was then developed for rapid on-site water sampling. The sampling kit included a portable electric drill, a copper mesh pocket, a piece of thin film, and a liner. Laboratory experiments indicated that the sampling remained in the linear uptake phase with this sampler to 8 min for the PAHs. Field test illustrated that this novel sampler was excellent for rapid on-site water sampling due to its short sampling period, high sampling efficiency and durability The thin film sampling kit facilitates on-site sampling, sample preparation, storage and transport. This new sampler is more user-friendly and easier to commercialize than previous samplers.

Sampling free and particle-bound chemicals using solid-phase microextraction and needle trap device simultaneously.

The possibility of sampling the free and particle-bound concentrations of organic compounds was studied using two different sampling techniques at the same time: needle trap device (NTD) and solid-phase microextraction (SPME). In this study, a mosquito coil was used to produce gaseous (free) and particle-bound compounds. Allethrin, the active ingredient in mosquito coils, was chosen as the target analyte. Under the same sampling conditions, the amount of allethrin extracted from the mosquito-coil smoke was higher for the NTD compared to the SPME fiber, while the extracted amounts were almost the same for both devices when sampling gaseous samples of allethrin. These results can be explained by the fact that the SPME fiber can only extract free molecules (based on diffusion), whereas the NTD, an exhaustive sampling device, collects both free and particle-bound allethrin. Breakthrough for NTD and carryover for both NTD and SPME were negligible under the given sampling and desorption conditions.

Recent developments in solid-phase microextraction.

The main objective of this review is to describe the recent developments in solid-phase microextraction technology in food, environmental and bioanalytical chemistry applications. We briefly introduce the historical perspective on the very early work associated with the development of theoretical principles of SPME, but particular emphasis is placed on the more recent developments in the area of automation, high-throughput analysis, SPME method optimization approaches and construction of new SPME devices and their applications. The area of SPME automation for both GC and LC applications is particularly addressed in this review, as the most recent developments in this field have allowed the use of this technology for high-throughput applications. The development of new autosamplers with SPME compatibility and new-generation metal fibre assemblies has enhanced sample throughput for SPME-GC applications, the latter being attributed to the possibility of using the same fibre for several hundred extraction/injection cycles. For LC applications, high-throughput analysis (>1,000 samples per day) can be achieved for the first time with a multi-SPME autosampler which uses multi-well plate technology and allows SPME sample preparation of up to 96 samples in parallel. The development and evolution of new SPME devices such as needle trap, thin-film microextraction and cold-fibre headspace SPME have offered significant improvements in performance characteristics compared with the conventional fibre-SPME arrangement.

Development of a syringe pump assisted dynamic headspace sampling technique for needle trap device.

This paper describes a new approach that combines needle trap devices (NTDs) with a dynamic headspace sampling technique (purge and trap) using a bidirectional syringe pump. The needle trap device is a 22-G stainless steel needle 3.5-in. long packed with divinylbenzene sorbent particles. The same sized needle, without packing, was used for purging purposes. We chose an aqueous mixture of benzene, toluene, ethylbenzene, and p-xylene (BTEX) and developed a sequential purge and trap (SPNT) method, in which sampling (trapping) and purging cycles were performed sequentially by the use of syringe pump with different distribution channels. In this technique, a certain volume (1 mL) of headspace was sequentially sampled using the needle trap; afterwards, the same volume of air was purged into the solution at a high flow rate. The proposed technique showed an effective extraction compared to the continuous purge and trap technique, with a minimal dilution effect. Method evaluation was also performed by obtaining the calibration graphs for aqueous BTEX solutions in the concentration range of 1-250 ng/mL. The developed technique was compared to the headspace solid-phase microextraction method for the analysis of aqueous BTEX samples. Detection limits as low as 1 ng/mL were obtained for BTEX by NTD-SPNT.

Fast analysis of volatile organic compounds and disinfection by-products in drinking water using solid-phase microextraction-gas chromatography/time-of-flight mass spectrometry.

A fast method was developed for the extraction and analysis of volatile organic compounds, including disinfection by-products (DBPs), with headspace solid-phase microextraction (HS-SPME) and gas chromatography/mass spectrometry (GC/MS) techniques. A GC/time-of-flight (TOF)-MS instrument, which had fast acquisition rates and powerful deconvolution software, was used. Under optimum conditions total runtime was 45s. Volatile organic compounds (VOCs), including purgeable A and B compounds (listed in US Environmental Protection Agency method 624), were identified in standard water samples. Extraction times were 1min for more volatile compounds and 2min for less volatile compounds. The method was applied to the analysis of water samples treated under different disinfection processes and the results were compared with those from a liquid-liquid extraction method.

Equilibrium in-fiber standardization method for determination of sample volume by solid phase microextraction.

This paper describes an in-fiber standardization method by Solid Phase Microextraction (SPME) for the determination of a sample volume. After loading a specific amount of standard, the volumetric standard, on a PDMS-coated fiber (n(0)), the fiber was exposed in the headspace of sample vials containing different volumes of water. The amount of standard that remained on the fiber after equilibrium (n(f)), which was determined with gas chromatography/mass spectrometry (GC/MS), depends on the volume of the sample. Naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, 1-ethylnaphthalene, and 2-ethylnaphthalene were chosen as volumetric standards based on theoretical calculations. The effect of loading time, exposure time, and exposure temperature were investigated. The effect of the matrix was also studied, analyzing both water and wine samples. Precision and accuracy of the method were obtained for each standard in both water and wine. The partition coefficients of the compounds between the fiber and the sample (K(fs)) and between the headspace and the sample (K(hs)) were obtained by plotting n(0)/n(f)versus sample volume.