Biomedical subjects

J Koziel

Publications and source records attributed to J Koziel.

3 recordsLinked to original sources

PubMed2001

Design and validation of portable SPME devices for rapid field air sampling and diffusion-based calibration.

The use of SPME fibers coated with porous polymer solid phases for quantitative purposes is limited due to effects such as interanalyte displacement and competitive adsorption. For air analysis, these problems can be averted by employing short exposure times to air samples flowing around the fiber. In these conditions, a simple mathematical model allows quantification without the need of calibration curves. This work describes two portable dynamic air sampling (PDAS) devices designed for application of this approach to nonequilibrium SPME sampling and determination of airborne volatile organic compounds (VOCs). The use of a PDAS device resulted in greater adsorbed VOC mass compared to the conventional SPME extraction in static air for qualitative screening of live plant aromas and contaminants in indoor air. For all studied air samples, an increase in the number of detected compounds and sensitivity was also observed. Quantification of aromatic VOCs in indoor air was also carried out using this approach and the PDAS/SPME device. Measured VOC concentrations were in low parts-per-billion by volume range using only 30-s SPME fiber exposure and were comparable to those obtained with a standard NIOSH method 1501. The use of PDAS/SPME devices reduced the total air sampling and analysis time by several orders of magnitude compared to the NIOSH 1501 method.

Journal Article↗

PubMed2001

Diffusion-based calibration for SPME analysis of aqueous samples.

When an SPME fiber is exposed for a short period of time to a flowing fluid sample, the amount of extracted analyte depends on its diffusion coefficient in the matrix medium, and it can be correlated to its concentration using a simple mathematical model. This work discusses the extension of this approach, already validated for gaseous samples and SPME fibers coated with strong adsorbent coatings, to the diffusion-based quantification of analytes present in aqueous samples. Dilute aqueous solutions of aromatic hydrocarbons were used as model samples and vials were modified to use conventional magnetic agitation with controlled tangential flow of the test solution around the fiber. It was demonstrated that, with proper selection of the stirring speed and sampling time, the same diffusion-based quantitative model used for gas samples could be employed. Under optimal conditions, the concentrations of the evaluated aromatic hydrocarbons were estimated with relative standard deviations between 0.8 and 3.6% and without deviation from the expected values within this precision range. Considering the extraction times involved, between 30 and 60 s, the approach here presented is the fastest possible technique for direct extraction of analytes from liquid samples.

Journal Article↗

PubMed2000

Air sampling with porous solid-phase microextraction fibers

A new, rapid air sampling/sample preparation methodology was investigated using adsorptive solid-phase microextraction (SPME) fiber coatings and nonequilibrium conditions for volatile organic compounds (VOCs). This method is the fastest extraction technique for air sampling at typical airborne VOC concentrations. A theoretical model for the extraction was formulated based on the diffusion through the interface between the sampled (bulk) air and the SPME coating. Parameters that affect the extraction process including sampling time, air velocity, air temperature, and relative humidity were investigated with the porous (solid) PDMS/DVB and Carboxen/PDMS coatings. Very short sampling times from 5 s to 1 min were used to minimize the effects of competitive adsorption and to calibrate the extraction process in the initial linear extraction region. The predicted amounts of extracted mass compared well with the measured amounts of target VOCs. Findings presented in this study extend the existing fundamental knowledge related to sampling/sample preparation with SPME, thereby enabling the development of new sampling devices for the rapid sampling of air, headspace, water, and soil.

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