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Biomedical subjects

Janusz Pawliszyn

Publications and source records attributed to Janusz Pawliszyn.

At least 73 records · Page 4Linked to original sources
PubMed2004

Analysis of proteins by CE, CIEF, and microfluidic devices with whole-column-imaging detection.

The recently developed whole-column-imaging detection technique for capillary electrophoresis (CE) and capillary isoelectric focusing (CIEF), a commercial whole-column-imaged CIEF instrument and its standard operation protocol are introduced. Furthermore, new developments and applications of whole-column-imaging detection in protein-protein interaction study, in protein separation using microfluidic devices and CIEF methods without carrier ampholytes, as well as in 2D separation techniques are reviewed. Miniaturization of whole-column-imaging CIEF and axially illuminated fluorescence whole-column-imaging CIEF are also discussed.

2S Albumins, Plant↗
PubMed2003

Microwave-assisted headspace solid-phase microextraction for the analysis of bioemissions from Eucalyptus citriodora leaves.

Microwave-assisted headspace solid-phase microextraction (MA-HS-SPME) was developed as a simple and effective method for fast sampling of volatile organic compounds (VOCs) from Eucalyptus citriodora Hook (E. citriodora) leaves. During microwave heating, a simple shielding device made of aluminum foil was used to protect the SPME fiber from microwave irradiation while allowing the sample to be heated. A room temperature water bath was also used to allow microwave heating to be conducted in a more controlled manner. The inner heating caused by microwave irradiation dramatically accelerated the emission of VOCs from the sample, but no marked change in headspace temperature in the sample vial was found. Under optimum conditions, the extraction efficiencies obtained with microwave heating were much higher than those obtained without microwave heating for all fibers used, namely, 7-microm polydimethylsiloxane (PDMS), 100-microm polydimethylsiloxane (PDMS), 65-microm polydimethylsiloxane/divinylbenzene (PDMS/DVB), and 75-microm carboxen/polydimethylsiloxane (CAR/PDMS). The improvement of extraction efficiency using MA-HS-SPME allowed more VOC events to be detected, with more balanced extraction of VOCs of lower and higher molecular masses. Moreover, a good linear relationship was found between sample size and GC-FID response (total peak area of VOCs), indicating the usefulness of MA-HS-SPME for quantitative analysis of individual volatile compounds in E. citriodora leaves.

Chromatography, Gas↗
PubMed2003

Correlations between pulp properties of eucalyptus clones and leaf volatiles using automated solid-phase microextraction.

Analysis of biogenic volatile organic compounds (BVOC) of 14 Eucalyptus clones has been performed using an automated headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography (GC)/ion trap mass spectrometry (ITMS) method. Correlations between pulp properties of Eucalyptus clones and the BVOC of their leaf headspaces were studied. The compounds alpha-terpineol and the sesquiterpene beta-eudesmol were positively correlated with S5, a property related to the hemicelluose content in the pulp. Qualitative results obtained with automated HS-SPME were sufficient to group together the same species and related hybrids through cluster analysis and were confirmed through principal component analysis. A preliminary separation of the essential oils of Eucalyptus dunnii through comprehensive two-dimensional gas chromatography (GC x GC) showed approximately 580 peaks compared to approximately 60 in a typical GC/ITMS first-dimension chromatogram. The potential of HS-SPME coupled to GC x GC to improve the separation of Eucalyptus volatiles and other plant essential oils looks extremely promising for new applications of unsupervised learning methods.

Autoanalysis↗
PubMed2003

On-site monitoring of biogenic emissions from Eucalyptus dunnii leaves using membrane extraction with sorbent interface combined with a portable gas chromatograph system.

Membrane extraction with sorbent interface, combined with a portable gas chromatograph system (MESI-Portable GC) for continuous on-line monitoring of biogenic volatile organic compounds (BVOCs) emissions (from leaves of Eucalytus dunnii in a greenhouse), is presented herein. A sampling chamber was designed to facilitate the extraction and identification of the BVOCs emitted by the Eucalytus dunnii leaves. Preliminary experiments, including; enrichment times, microtrap temperatures, stripping gas flow rates, and desorption temperatures were investigated to optimize experimental parameters. The main components of BVOCs released by the Eucalytus dunnii leaves were identified by comparing the retention times of peaks with those of authentic standard solutions. They were then confirmed with solid phase microextraction coupled with gas chromatography and mass spectrometry (SPME-GC-MS). BVOC emission profiles of [small alpha]-pinene, eucalyptol, and [gamma]-terpinene emitted by intact and damaged Eucalytus dunnii leaves were obtained. The findings suggest that the MESI-Portable GC system is a simple and useful tool for field monitoring changes in plant emissions as a function of time.

Chromatography, Gas↗
PubMed2003

Calibration for on-site analysis of hydrocarbons in aqueous and gaseous samples using solid-phase microextraction.

Rapid sampling and sample preparation methodology was investigated using adsorptive poly(dimethylsiloxane)/divinylbenzene and Carboxen/poly(dimethylsiloxane) solid-phase microextraction (SPME) fiber coatings and volatile aromatic hydrocarbons (BTEX: benzene, toluene, ethylbenzene, and o-xylene). A flow-through system was used to generate a standard aqueous solution of BTEX as model sample with known linear velocity. Parameters that affect the extraction process, including sampling time, concentration, water velocity, and temperature, were investigated. Very short sampling times from 10 s and sorbents with strong affinity and large capacity were used to ensure the effect of '"zero sink" and to calibrate the extraction process in the initial linear extraction region. Several different concentrations were investigated, and it was found that mass uptake changes with concentration linearly. The increase of water velocity increases mass uptake, though the increase is not linear. Temperature does not affect mass uptake significantly under typical field sampling conditions. To further accurately describe rapid SPME analysis of aqueous samples, a new model translated from heat transfer to a circular cylinder in cross-flow was used. An empirical correlation to this model was used to predict the mass-transfer coefficient. Findings indicate that predicted mass uptake compares well with experimental mass uptake. The new model was tested for rapid air sampling, and it was found that this new model also predicted rapid air sampling accurately. Findings presented in this study extend the existing fundamental knowledge related to rapid sampling/sample preparation with SPME.

Journal Article↗
PubMed2003

Capillary isoelectric focusing of proteins with liquid core waveguide laser-induced fluorescence whole column imaging detection.

A capillary isoelectric focusing (CIEF) system with liquid core waveguide (LCW) laser-induced fluorescence whole column imaging detection was developed in this study. A Teflon AF 2400 capillary was used as both the separation channel and the axially illuminated LCW. The excitation light was introduced at one end of the capillary, and propagated forward within the capillary. As the Teflon AF 2400 capillary has a refractive index (n = 1.29-1.31) lower than that of water (n = 1.33), total internal reflection was very apparent The employment of the Teflon AF 2400 capillary avoided the use of high refractive index additives such as glycerol, accommodating the system to wider applications. Due to its inert chemical properties, the capillary exhibited limited protein adsorption and electroosmotic flow; thus, the need for capillary preconditioning with polymeric solution and the addition of polymeric additives into the sample mixture can be avoided. Three types of proteins, naturally fluorescent proteins, covalently labeled proteins, and noncovalently labeled proteins, were examined using this method. CIEF under denaturing conditions was also explored, and several advantages over the native mode were found. When compared to a commercially available instrument with UV detection, the separation efficiency and peak capacity were similar while the detection sensitivity was enhanced by 3-5 orders of magnitude.

Electrophoresis, Capillary↗
PubMed2003

CE in a nonuniform capillary modulated by a cylindrical insert, and zone-narrowing effects during sample injection.

The electrophoretic behavior of an analyte in a capillary consisting of two parts of different cross section has been investigated. Modulation of the cross-sectional area of the separation channel has been achieved by inserting a cylindrical fiber different distances into the capillary. It was shown that the zone injected into the capillary part with smaller cross section could be moved using electromigration into the wider part of the capillary with zone compression. As we observed, the zone narrowed longitudinally in the wide part of the capillary in accordance with the ratio of the electric field strength in the two parts of the capillary. The concentration of plug introduced into the capillary by electroinjection can be increased by use of low-conductivity sample buffer. Efficient introduction of extracted analytes desorbed from an SPME fiber to the separation channel was achieved using this approach. Thermoinduced effects caused by temperature increase in the narrow part of the capillary and their influence on sample stacking are analyzed. Possible applications of the effect observed to the sample introduction optimization are also discussed in this study.

Letter↗
PubMed2003

Sample preparation: quo vadis?

The sample preparation step in an analytical process typically consists of an extraction procedure that results in the isolation and enrichment of components of interest from a sample matrix. Extraction can vary in degree of selectivity, speed, and convenience and depends not only on the approach and conditions used but on the geometric configurations of the extraction phase. Increased interest in sample preparation research has been generated by the introduction of nontraditional extraction technologies. These technologies address the need for reduction of solvent use, automation, and miniaturization and ultimately lead to on-site in situ and in vivo implementation. These extraction approaches are frequently easier to operate but provide optimization challenges. More fundamental knowledge is required by an analytical chemist not only about equilibrium conditions but, more importantly, about the kinetics of mass transfer in the extraction systems. Optimization of this extraction process enhances overall analysis. Proper design of the extraction devices and procedures facilitates convenient on-site implementation, integration with sampling, and separation/quantification, automation, or both. The key to rational choice, optimization, and design is an understanding of the fundamental principles governing mass transfer of analytes in multiphase systems. The objective of this perspective is to summarize the fundamental aspects of sample preparation and anticipate future developments and research needs.

Journal Article↗
PubMed2003

On-site calibration method based on stepwise solid-phase microextraction.

A stepwise solid-phase microextraction (SPME) method was developed for on-site calibration of SPME for volatile organic compounds analysis. In this approach, a 75-microm Carboxen-polydimethylsiloxane coated fibre was loaded with a prior to exposure to samples of interest Extraction time for the target analytes can be controlled independently from that of the standard, and the response factors for the target analytes can be adjusted accordingly. A good reproducibility of the response factors for BTEXs (benzene, toluene, ethylbenzene and xylenes) was obtained with stepwise SPME. Satisfactory results were obtained by using this method for quantitative analysis of BTEXs in the air of a gas station when tetrachloroethylene was used as a standard. The introduction of standard via the stepwise SPME procedure makes SPME more useful in field applications. It can be used to detect leaks, contaminations and losses from loading of a standard onto a fibre to introduction of the fibre to an analytical instrument. However, this method cannot be used for compensation of sample matrix effects.

Benzene↗
PubMed2003

Time-weighted average passive sampling with a solid-phase microextraction device.

A modified Solid-Phase Microextraction (SPME) device has been used as a passive sampler to determine the time-weighted average (TWA) concentration of volatile organic compounds (VOCs) in air. Unlike conventional sampling with SPME, in which the fiber is extended outside its needle housing, during TWA passive sampling, the fiber is retracted a known distance into its needle housing. The SPME passive sampler collects the VOCs by the mechanism of molecular diffusion and sorption on to a coated fiber as collection medium. This process has been shown to be described by Fick's first law of diffusion, whereby determination of the amounts of analytes accumulated over time enable measurement of the TWA concentration to which the sampler was exposed. A series of fibers, 100-microm poly(dimethylsiloxane), 65-microm poly(dimethylsiloxane)/divinylbenzene, and 75-microm Carboxen/poly(dimethylsiloxane), were tested for their "zero sink", face velocity, and response time behavior. Of the fibers tested, that coated with 75-microm Carboxen/poly(dimethylsiloxane) was found to be an excellent passive sampler for VOCs. TWA passive sampling with a SPME device was shown to be almost independent of face velocity and to be more tolerant of high and low analyte concentrations and long and short sampling times, because of the ease with which the diffusion path length could be changed. It was found that environmental conditions, e.g., temperature, pressure, relative humidity, and ozone, have little or no effect on sampling. The 75-microm Carboxen/poly(dimethylsiloxane) fiber can retain VOCs for up to two weeks without significant loss. When the SPME device was tested in the field and the results were compared with those from National Institute of Occupational Health and Safety method 1501, good agreement was obtained.

Air Pollutants, Occupational↗
PubMed2003

Solid-phase microextraction of volatile compounds from the chopped leaves of three species of Eucalyptus.

Headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography and ion-trap mass spectrometry has been used to identify biogenic volatile organic compounds present in the headspace of chopped leaves of Eucalyptus (E.) dunnii, E. citriodora, and E. saligna. A simple HS-SPME method entailing 30 min of extraction at 30 degrees C was developed for this purpose. Thirty compounds were identified in the headspace of 60 juvenile chopped Eucalyptus leaves, and another 30 were tentatively identified. The presence of compounds such as (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene (TMNT), (E,E)-alpha-farnesene, (E,E,E)-3,7,11,15-tetramethyl-1,3,6,10,14-hexadecapentaene (TMHP), beta-caryophyllene, alpha-humulene, germacrene D, and beta-cubebene in the headspace of the leaves but not in the essential oils from the same Eucalyptus trees and information about the infochemical roles of some of these compounds in other living plant systems suggest they might play a bioactive role in Eucalyptus leaves.

Eucalyptus↗
PubMed2003

Thin-film microextraction.

The properties of a thin sheet of poly(dimethylsiloxane) (PDMS) membrane as an extraction phase were examined and compared to solid-phase microextraction (SPME) PDMS-coated fiber for application to semivolatile analytes in direct and headspace modes. This new PDMS extraction approach showed much higher extraction rates because of the larger surface area to extraction-phase volume ratio of the thin film. Unlike the coated rod formats of SPME using thick coatings, the high extraction rate of the membrane SPME technique allows larger amounts of analytes to be extracted within a short period of time. Therefore, higher extraction efficiency and sensitivity can be achieved without sacrificing analysis time. In direct membrane SPME extraction, a linear relationship was found between the initial rate of extraction and the surface area of the extraction phase. However, for headspace extraction, the rates were somewhat lower because of the resistance to analyte transport at the sample matrix/headspace barrier. It was found that the effect of this barrier could be reduced by increasing either agitation, temperature, or surface area of the sample matrix/headspace interface. A method for the determination of PAHs in spiked lake water samples was developed based on the membrane PDMS extraction coupled with GC/MS. A linearity of 0.9960 and detection limits in the low-ppt level were found. The reproducibility was found to vary from 2.8% to 10.7%.

Chromatography, Gas↗
PubMed2002

SPME applied to the study of volatile organic compounds emitted by three species of Eucalyptus in situ. Solid-phase micro extraction.

Headspace solid-phase microextraction coupled to gas chromatography/ion trap mass spectrometry-65 microm polydimethylsiloxane/divinylbenzene (PDMS/DVB) was used to identify and monitor the emission patterns of biogenic volatile organic compounds from leaves of Eucalyptus dunnii, Eucalyptus saligna, and Eucalyptus citriodora in situ. Short extractions (1 min) were performed every 30 min for periods of 8-10 h during 24 days taking advantage of the high capacity of this porous polymer coating. Forty-two compounds were detected and 20 identified in the headspace of E. saligna leaves, and 19 of 27 compounds were identified in the headspace of E. dunnii leaves. The emission pattern of (E)-beta-ocimene and rose oxide suggests that they may play a bioactive role in Eucalyptus.

Acyclic Monoterpenes↗
PubMed2002

Analysis of polar pesticides in water and wine samples by automated in-tube solid-phase microextraction coupled with high-performance liquid chromatography-mass spectrometry.

A simple and sensitive method for the determination of polar pesticides in water and wine samples was developed by coupling automated in-tube solid-phase microextraction (SPME) to high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS). To achieve optimum performance, the conditions for both the in-tube SPME and the ESI-MS detection were investigated. In-tube SPME conditions were optimized by selecting the appropriate extraction parameters, especially the stationary phases used for SPME. For the compounds studied, a custom-made polypyrrole (PPY)-coated capillary showed superior extraction efficiency as compared to several commercial capillaries tested, and therefore, it was selected for in-tube SPME. The influence of the ethanol content on the performance of in-tube SPME was also investigated. It was found that the amount of pesticides extracted decreased with the increase of ethanol content in the solutions. The ESI-MS detection conditions were optimized as follows: nebulizer gas, N2 (30 p.s.i.; 1 p.s.i.=6894.76 Pa); drying gas, N2 (10 l/min, 350 degrees C); capillary voltage, 4500 V; ionization mode, positive; mass scan range, 50-350 amu; fragmentor voltage, variable depending on the ions selected. Due to the high extraction efficiency of the PPY coating and the high sensitive mass detection, the detection limits (S/N = 3) of this method for the compounds studied are in the range of 0.01 to 1.2 ng/ml, which are more than one order of magnitude lower than those of the previous in-tube SPME-HPLC-UV method. A linear relationship was obtained for each analyte in the concentration range of 0.5 to 200 ng/ml with MS detection. This method was applied to the analysis of phenylurea and carbamate pesticides in spiked water and wine samples.

Automation↗
PubMed2002

Breath analysis and monitoring by membrane extraction with sorbent interface.

An analytical system consisting of a sampling chamber, membrane extraction module, sorbent trap and gas chromatograph with flame ionization or ion mobility detector was used for on-line monitoring of the composition of the last 250 mL portion of human expired breath. The sampling chamber consisted of a tube fitted with check valves on both ends to allow the air to pass through during expiration, but not to return or allow mixing with ambient air. The last portion of breath was held in the chamber at the end of breath expiration. The organic components in the trapped breath were transferred to the carrier gas by permeation through the membrane in the extraction module and were concentrated in the sorbent trap before introduction as a sharp plug on the front of chromatographic column. Moisture in the breath did not penetrate the membrane to a substantial degree. This system was used to investigate presence of acetone as a biologically important marker of human health as well as exposure to volatile compounds.

Acetone↗
PubMed2002

Sampling and monitoring of biogenic emissions by eucalyptus leaves using membrane extraction with sorbent interface (MESI).

Membrane extraction with sorbent interface (MESI) has been applied to monitor plant fragrance volatiles emitted into indoor air. The main components of the MESI system are a membrane module and a trap, which can be connected directly to a GC or GC-MS for simultaneous multicomponent extraction and monitoring. A polydimethylsiloxane (PDMS) membrane and two different traps, PDMS and Tenax, as well as a DC current supply for trap desorption have been applied in this research. After the membrane module is placed in contact with the plant, the MESI/GC-MS provides semicontinuous characterization of volatile compounds emitted. The MESI device has been applied to monitor the biogenic volatile organic compounds released during the first 8 h after a branch was cut from a Eucalyptus dunnii tree. The study demonstrates that the MESI system is a simple and useful tool for monitoring changes in emission processes as a function of time.

Chemistry Techniques, Analytical↗
PubMed2002

Electrochemically controlled solid-phase microextraction based on conductive polypyrrole films.

Solid-phase microextraction (SPME) fiber coatings based on conductive polypyrrole films were prepared for the electrochemical extraction and desorption of ionic analytes. Simple preparation of each of the PPY extraction coatings on a platinum wire was possible with a constant potential method, but more importantly, cycling of the film between oxidation and reduction potentials facilitated the extraction and desorption of ionic analytes. The analytes were desorbed into a sample aliquot of water and were determined by flow injection analysis using a mass spectrometer. The fiber coatings and the developed electrochemical SPME method were found to be stable and reproducible (RSD < 5%; N = 5) and could be extended to several cations and anions, confirming the versatility of the approach. Preconcentration of the analyte on the fiber was also possible by repeating the processes to increase the amount of analyte extracted.

Letter↗