In vivo study of triazine herbicides in plants by SPME

Sample preparation techniques for protein binding measurement in radiopharmaceutical approaches: A short review

Plasma protein binding (PPB) measurement is a key step in radiopharmaceutical studies for the development of positron emission tomography (PET) radioligands. PPB refers to the binding degree of a radioligand, radiotracer, or drug to blood plasma proteins or tissues after administration into the body. Several techniques have been successfully developed and applied for PPB measurement of PET radioligands. However, there is room for progress among these techniques in relation to duration time, adaptability with nonpolar radioligands, in vivo measurement, specificity, and selectivity. This mini review gives a brief overview of advances, limitations, and prospective applications of commercially-available PPB methods.

Evaluation of a multi-fiber exchange solid-phase microextraction system and its application to on-site sampling

Until recently, multiple solid-phase microextraction fibers could not be automatically desorbed in a single gas chromatographic sequence without manual intervention from an operator. This drawback had been a critical issue, particularly during the analysis of numerous on-site samples taken with various fiber assemblies. Recently, a Multi-Fiber Exchange system, designed to overcome this flaw found in other commercially available autosamplers, was released. In the current research, a critical evaluation of the Multi-Fiber Exchange system performance in terms of storage stability and long-term operation is presented. It was established in the course of our research that the Multi-Fiber Exchange system can operate continuously and precisely for multiple extraction/injection cycles. However, when the effect of residence time of commercial fibers on the Multi-Fiber Exchange tray was evaluated, results showed that among the evaluated fiber coatings, Carboxen/polydimethylsiloxane was the only coating capable of efficient storage on the tray for up to 24 h after field sampling without suffering significant loss of analytes (≤10% for benzene, toluene, ethylbenzene, o-xylene, decane, and limonene). Additionally, the system capability for high-throughput analysis was demonstrated by the unattended desorption of multiple fibers after on-site sampling of toluene, indoor air levels, in a polymer synthesis lab.

Development of needle trap technology for on-site determinations: active and passive sampling

This study presents a thorough evaluation of new prototypes of extended tip needle trap devices (NT), as well as their application to in situ sampling of biological emissions and active/passive on-site sampling of indoor air. A new NT prototype was constructed with a side hole above the sorbent and an extended tip that fits inside the restriction of the narrow neck liner to increase desorption efficiency. New prototype needles were initially packed with divinylbenzene particles at SGE Analytical Science for the purpose of studying biogenic emissions of pine trees. Prior to their final application, they were evaluated in terms of robustness after multiple use (n > 10), as well as amount extracted of volatile organic compounds (VOCs). An ANOVA test for all the probes showed that at a 95% level of confidence, there were not statistical differences observed among the 9 NTs tested. In addition, the needles were also packed in laboratory with synthesized highly cross-linked PDMS as a frit to immobilize carboxen (Car) particles for spot sampling. For passive sampling, the needles were packed with Car particles embedded in PDMS to simplify calculations in passive mode. The use of NTs as spot samplers, as well as a passive sampler under controlled conditions in the laboratoryyielded a relative standard deviation of less than 15%. Finally, a new, reusable and readily deployable penlike diffusive sampler for needle traps (PDS-NT) was built and tested. Application of the PDS-NT in combination with NT-spot sampling toward the analysis of indoor air in a polymer synthesis laboratory showed good agreement between both techniques for the analyte studied, yielding averages of 0.03 and 0.025 ng/mL of toluene, respectively.

A solid-phase microextraction method for the in vivo sampling of MTBE in common reed (Phragmites australis)

Phytoscreening of phytoremediation-based plantings is discussed as a promising monitoring tool in literature. We developed and applied an analytical procedure for the in vivo sampling of methyl tert-butyl ether (MTBE) in the common reed (Phragmites australis) from a phytoremediation site highly polluted with MTBE. The approach uses solid-phase microextraction (SPME) with the SPME fibre directly introduced into the aerenchyma of the plant stem. For optimising the analytical procedure and estimating the capability of the proposed method, laboratory tests on the microcosm scale and field studies over one vegetation period were carried out. Furthermore, the results of in vivo SPME sampling were compared with those obtained with the traditional approach for analysing plants using dynamic headspace analysis. The MTBE signals detected within the plants were also correlated with the concentration in the water phase. The discussion of results showed the feasibility of the proposed method for a qualitative phytoscreening of volatile organic compounds present in wetland plants.

Time-weighted average SPME analysis for in planta determination of cVOCs

The potential of phytoscreening for plume delineation at contaminated sites has promoted interest in innovative, sensitive contaminant sampling techniques. Solid-phase microextraction (SPME) methods have been developed, offering quick, undemanding, noninvasive sampling without the use of solvents. In this study, time-weighted average SPME (TWA-SPME) sampling was evaluated for in planta quantification of chlorinated solvents. TWA-SPME was found to have increased sensitivity over headspace and equilibrium SPME sampling. Using a variety of chlorinated solvents and a polydimethylsiloxane/carboxen (PDMS/CAR) SPME fiber, most compounds exhibited near linear or linear uptake over the sampling period. Smaller, less hydrophobic compounds exhibited more nonlinearity than larger, more hydrophobic molecules. Using a specifically designed in planta sampler, field sampling was conducted at a site contaminated with chlorinated solvents. Sampling with TWA-SPME produced instrument responses ranging from 5 to over 200 times higher than headspace tree core sampling. This work demonstrates that TWA-SPME can be used for in planta detection of a broad range of chlorinated solvents and methods can likely be applied to other volatile and semivolatile organic compounds.

Phytoscreening for chlorinated solvents using rapid in vitro SPME sampling: application to urban plume in Verl, Germany

Rapid detection and delineation of contaminants in urban settings is critically important in protecting human health. Cores from trees growing above a plume of contaminated groundwater in Verl, Germany, were collected in 1 day, with subsequent analysis and plume mapping completed over several days. Solid-phase microextraction (SPME) analysis was applied to detect tetrachloroethene (PCE) and trichloroethene (TCE) to below nanogram/liter levels in the transpiration stream of the trees. The tree core concentrations showed a clear areal correlation to the distribution of PCE and TCE in the groundwater. Concentrations in tree cores were lower than the underlying groundwater, as anticipated; however, the tree core water retained the PCE:TCE signature of the underlying groundwater in the urban, populated area. The PCE:TCE ratio can indicate areas of differing degradation activity. Therefore, the phytoscreening analysis was capable not only of mapping the spatial distribution of groundwater contamination but also of delineating zones of potentially differing contaminant sources and degradation. The simplicity of tree coring and the ability to collect a large number of samples in a day with minimal disruption or property damage in the urban setting demonstrates that phytoscreening can be a powerful tool for gaining reconnaissance-level information on groundwater contaminated by chlorinated solvents. The use of SPME decreases the detection level considerably and increases the sensitivity of phytoscreening as an assessment, monitoring, and phytoforensic tool. With rapid, inexpensive, and noninvasive methods of detecting and delineating contaminants underlying homes, as in this case, human health can be better protected through screening of broader areas and with far faster response times.

Tissue-specific in vivo bioconcentration of pharmaceuticals in rainbow trout (Oncorhynchus mykiss) using space-resolved solid-phase microextraction

The space-resolved solid-phase microextraction (SR-SPME) technique was employed to study the tissue-specific bioconcentration of pharmaceuticals in live fish. The segmented design of the SPME fibers allowed for the simultaneous determination of pharmaceutical residues in fish dorsal-epaxial muscle and adipose tissue with a single SPME fiber. The miniaturized fiber endowed the technique with high spatial resolution allowing for quantification of analytes within adjacent, relatively small tissues of immature rainbow trout. The pre-equilibrium sampling and kinetic calibration approach yielded efficient and accurate quantitation of pharmaceuticals in fish tissue. The ability of the SPME method to repeatedly sample the same fish circumvents problems arising from interanimal variation, thus improving the precision of generated bioconcentration kinetic profiles. In vivo monitoring with SR-SPME was validated with in vitro liquid extraction of tissue samples using methanol. Of the nine compounds evaluated, five (atrazine, gemfibrozil, carbamazepine, ibuprofen, and fluoxetine) bioconcentrated in adipose and muscle tissue over the eight exposure days. Although the accumulation of analytes in both tissues was positively correlated, each compound partitioned with differing affinities as modified by their hydrophobicity and unique molecular structure. Water samples analyzed using the SPME technique yielded results similar to those determined by solid-phase extraction (SPE); however, SPME was more rapid and operationally much simpler. This study illustrates the application conditions for in situ SR-SPME while demonstrating the potential of these miniaturized SPME fibers for simultaneous in vivo repeated sampling of multiple tissues.

Comparison of microdialysis with solid-phase microextraction for in vitro and in vivo studies

Microdialysis (MD) and solid-phase microextraction (SPME) methods have been developed and compared through in vitro and in vivo studies. For in vitro study, both methods offered accurate and precise results for complex sample matrices by standard addition method. Compared to MD, the fully automated SPME procedure offered several advantages including high-throughput and more efficient sampling, less labor intensity, and capability for batch analysis. For in vivo study, although both techniques provided sampling with minimal perturbation to the system under study, SPME was more sensitive, precise and accurate, suitable for field sampling and had a wider application than MD. It demonstrated that SPME has the potential to replace MD for in vivo study.

Strategies for interfacing solid-phase microextraction with liquid chromatography

Solid-phase microextraction (SPME) techniques are equally applicable to both volatile and non-volatile analytes, but the progress in applications to gas-phase separations has outpaced that of liquid-phase separations. The interfacing of SPME to gas chromatographic equipment has been straight-forward, requiring little modification of existing equipment. The requirement of solvent desorption for non-volatile or thermally labile analytes has, however, proven challenging for interfacing SPME with liquid-phase separations. Numerous options to achieve this have been described in the literature over the past decade, with applications in several different areas of analysis. To date, no single strategy or interface device design has proven optimal. During method development analysts must select the most appropriate interfacing technique among the options available. Out of these options three general strategies have emerged: (1) use of a manual injection interface tee; (2) in-tube SPME; and (3) off-line desorption followed by conventional liquid injection. In addition, there has been interest in coupling SPME directly to electrospray ionisation and matrix-assisted laser desorption ionisation (MALDI) for mass spectrometry. Several examples of each of these strategies are reviewed here, and an overview of their use and application is presented.

Solid-phase microextraction-gas chromatography-time-of-flight mass spectrometry utilized for the evaluation of the new-generation super elastic fiber assemblies

The aim of this study was to evaluate the performance characteristics of the recently developed super elastic solid-phase microextraction (SPME) fibers. The fiber needle, plunger and fiber core are manufactured with a special type of flexible alloy that exhibits excellent shape memory and tensile strength. This material makes the assemblies more robust, permitting several hundreds of analyses in a sequence, which is one of the ways to improve the robustness and sample throughput of automated SPME methods. The design and size of the needle utilized in the new fiber assemblies is discussed here, as well as the use of a septum-free injector replacement and a low-volume direct injection glass liner placed in the GC inlet. Deionized water and pump oil samples spiked with target volatile compounds (McReynold's probes and toluene) were used for the purposes of the presented study. A fully automated SPME sample preparation technique was combined with the GC-TOFMS system for the chromatographic separation and identification/quantification of the target analytes.

Determination of 17 Kinds of Banned Organochlorine Pesticides in Water by Activated Carbon Fiber-Solid Phase Microextraction Coupled with GC-MS

Activated carbon fiber (ACF) as extraction fiber for solid-phase microextraction (SPME) and its application for the analysis of banned organochlorine pesticides (OCPs) were investigated. Firstly, ACF was activated by different concentration of zinc chloride, which indicated that ACF activated by 60% zinc chloride had a reasonable specific surface area, pore volume and pore distribution. Secondly, the parameters for the ACF-SPME procedure, the adsorption and desorption conditions, were also optimized when coupled with gas chromatography-mass spectrometry (GC-MS). Thirdly, the ACF-SPME was used to analyze 17 kinds of OCPs in water. The linearity of most pesticides was found to be between 0.2 and 50 microg/l with GC-MS under the selected ion monitoring (SIM) acquisition mode. The limits of detection (LOD) at the sub microg/l were obtained. The work demonstrated here shows that ACF is a promising alternative for the SPME procedure.

Structure selectivity in degradation and translocation of polychlorinated biphenyls (Delor 103) with a Pleurotus ostreatus (oyster mushroom) culture

The biodegradation of polychlorinated biphenyls (PCBs), formerly applied in technical mixtures called Delor 103, was realized by the white rot fungus Pleurotus ostreatus. Besides the efficiency of degradation the translocation of PCBs into the fruit bodies grown during cultivation on straw were of special interest. The selectivity of PCBs degradation is discussed on the basis of structural features of the individual congeners. The most important structural factors affecting the degradation efficiency are indicated with molecular descriptors. Basic dependences of the degradation efficiency of congeners on their chlorination grade and ortho chlorosubstitution could be proved. Additionally, other structural parameters such as the number and position of non-substituted carbon in the biphenyl molecule also affect the degradation results. Apart from the removal of Delor 103 the translocation of PCB isomers into the fruit bodies growing up during cultivation was observed. The structural features assisting the transport of PCB congeners from the straw substrate colonized with mushroom mycelium (straw/mycelium) to the mushroom fruit bodies are also relevant for the degradation mechanism but act reversely. Among the chlorination grade, structural parameters such as the number of para and adversely positioned chlorines or the number of occupied para and meta positions contribute to an accumulation of individual PCB congeners in the mushrooms. In total, only few PCB amounts (below 0.1% of the initially present PCBs in straw) were transported into the fruit bodies and a dangerous PCB contamination was never reached while the experiment. A combination of accelerated solvent extraction and GC-MS analysis was the analytical basis for the investigation presented.