In vivo Solid Phase Microextraction for Brain Tissue Analysis

New solid phase microextraction (SPME) method was developed for brain tissue bioanalysis on a liquid chromatography mass spectrometry platform. To achieve set objectives, in vivo SPME desorption process was optimized for high throughput analysis through the development of a desorption device. Subsequently, new SPME coatings were developed for the extraction of polar neurotransmitters from biological matrices. In a targeted analysis, in vivo SPME was used to monitor of changes in the concentrations of endogenous compounds (multiple neurotransmitters) and exogenous drugs (carbamazepine and cimetidine) in the striatum of the rat brain extracellular fluid. For the first time, SPME was used for quantitative analysis of neurotransmitters and also study spacial distribution of other drugs in different regions of the brain extracellular fluid. A new approach was developed for improved metabolites coverage in a global non-targeted metabolomics studies. The proposed in vivo method showed how complementary results can be obtained through the combination of microdialysis and SPME for simultaneous sampling of the brain extracellular fluid. Finally, in a clinical application, SPME was used to monitor changes in the concentration of multiple neurotransmitters during deep brain stimulation of the pre-frontal cortex of the brain

Investigations of 2-alkyl-3-methoxypyrazines in three ladybug species and wine /

Investigations of 2-alkyl-3-methoxypyrazines (2-isopropyl-3-methoxypyra2ine, 2- secbutyl-3-methoxypyrazine and 2-isobutyl-3-niethoxypyrazine) in ladybug species {Coleoptera: Coccinellidae) and wine samples have been conducted. Headspace sampling coupled with gas chromatography-mass spectrometry was used to determine amounts of 2-alkyl-3-methoxypyra2ines in the ladybug species. Hippodamia convergens had the highest amount of alkybnethoxypyrazines, followed by Harmoma axyridis and the least in Coccinella septempunctata. Using a solvent extraction method, the precoccinelline alkaloid was found present in Hippodamia convergens and Coccinella septempunctata but not Harmonia axyridis. Steam distillation followed by a soHd phase extraction method as a sample preparation technique, enhanced detection while the isotope dilution method afforded accurate quantitation of the alkyknethoxypyrazines in the wine samples. Both ladybug-tainted and commercial wine samples were found to contain the 2- alkyl-3-methoxypyrazines. Wine samples prepared in 2001 generally contained higher levels than the corresponding 2003 samples. Levels of the 2-alkyl-3-methoxypyrazines found in the commercial wines ranged from a minimum value of 6 ng/L to 260 ±10 ng/L. Analyses revealed that for both ladybug species and wine samples, the 2- isopropyl-3-methoxypyrazine had the highest concentration, followed by 2-isobutyl- 3-methoxypyrazine and the least being the 2-secbutyl-3-methoxypyrazine. Possible contamination of the wine samples by ladybugs is thoroughly discussed. Furthermore, attempts to remove or reduce the levels of the alkylmethoxypyrazines with molecularly imprinted polymers from wine samples are presented in detail

A non-invasive method for in vivo skin volatile compounds sampling

•Development of a simple, non-invasive method and device for in vivo skin volatiles sampling.•Full investigation off actors that influenced the in vivo sampling reproducibility.•Comparison of headspace sampling and direct contact sampling modes.•Proposal of effective protocols for membrane storage before and after sampling.•Application of the proposed method for dietary biomarkers investigation. The use of volatile organic compounds (VOCs) emanating from human skin presents great potential for skin disease diagnosis. These compounds are emitted at very low concentrations. Thus, the sampling preparation step needs to be implemented before gas chromatography–mass spectrometry (GC–MS) analysis. In this work, a simple, non-invasive headspace sampling method for volatile compounds emanating from human skin is presented, using thin film as the extraction phase format. The proposed method was evaluated in terms of reproducibility, membrane size, extraction mode and storage conditions. First, the in vial sampling showed an intra- and inter-membrane RSD% less than 9.8% and 8.2%, respectively, which demonstrated that this home-made skin volatiles sampling device was highly reproducible with regard to intra-, inter-membrane sampling. The in vivo sampling was influenced not only by the skin metabolic status, but also by environmental conditions. The developed sampling set-up (or “membrane sandwich”) was used to compare two different modes of sampling: headspace and direct sampling. Results demonstrated that headspace sampling had significantly reduced background signal intensity, indicating minimized contamination from the skin surface. In addition, membrane storage conditions both before and after sampling were fully investigated. Membranes stored in dry ice for up to 72h after collection were tested and showed no or minimal change in volatile profiles. This novel skin volatile compounds sampling approach coupled with gas chromatography–mass spectrometry (GC–MS) can achieve reproducible analysis. This technique was applied to identify the biomarkers of garlic intake and alcohol ingestion. Dimethyl sulphone, allyl methyl sulfide and allyl mercaptan, as metabolites of garlic intake, were detected. In addition, alcohol released from skin was also detected using our “membrane-sandwich” sampling. Using the same approach, we analyzed skin VOCs from upper back, forearm and back thigh regions of the body. Our results show that different body locations share a number of common compounds (27/99). The area with most compounds detected was the upper back skin region, where the density of sebaceous glands is the highest