scholarly journals Optimization of Time-Weighted Average Air Sampling by Solid-Phase Microextraction Fibers Using Finite Element Analysis Software

Molecules ◽  
2018 ◽  
Vol 23 (11) ◽  
pp. 2736 ◽  
Author(s):  
Bulat Kenessov ◽  
Jacek Koziel ◽  
Nassiba Baimatova ◽  
Olga Demyanenko ◽  
Miras Derbissalin
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Solid Phase Microextraction ◽  
Solid Phase ◽  
Weighted Average ◽  
Internal Diameter ◽  
Analysis Software ◽  
Element Analysis ◽  
Time Weighted Average

Determination of time-weighted average (TWA) concentrations of volatile organic compounds (VOCs) in air using solid-phase microextraction (SPME) is advantageous over other sampling techniques, but is often characterized by insufficient accuracies, particularly at longer sampling times. Experimental investigation of this issue and disclosing the origin of the problem is problematic and often not practically feasible due to high uncertainties. This research is aimed at developing the model of the TWA extraction process and optimization of TWA air sampling by SPME using finite element analysis software (COMSOL Multiphysics, Burlington, MA, USA). It was established that sampling by porous SPME coatings with high affinity to analytes is affected by slow diffusion of analytes inside the coating, an increase of their concentrations in the air near the fiber tip due to equilibration, and eventual lower sampling rate. The increase of a fiber retraction depth (Z) resulted in better recoveries. Sampling of studied VOCs using 23 ga Carboxen/polydimethylsiloxane (Car/PDMS) assembly at maximum possible Z (40 mm) was proven to provide more accurate results. Alternative sampling configuration based on 78.5 × 0.75 mm internal diameter SPME liner was proven to provide similar accuracy at improved detection limits. Its modification with the decreased internal diameter from the sampling side should provide even better recoveries. The results obtained can be used to develop a more accurate analytical method for determination of TWA concentrations of VOCs in air using SPME. The developed model can be used to simulate sampling of other environments (process gases, water) by retracted SPME fibers.

scholarly journals Optimization of Time-Weighted Average Air Sampling by Solid-Phase Microextraction Fibers Using Finite Element Analysis Software

2018 ◽  
Author(s):  
Bulat Kenessov ◽  
Jacek A. Koziel ◽  
Nassiba Baimatova ◽  
Olga P. Demyanenko ◽  
Miras Derbissalin
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Solid Phase Microextraction ◽  
Solid Phase ◽  
Weighted Average ◽  
Air Sampling ◽  
Internal Diameter ◽  
Analysis Software ◽  
Element Analysis ◽  
Time Weighted Average

Determination of time-weighted average (TWA) concentrations of volatile organic compounds (VOCs) in air using solid-phase microextraction (SPME) is advantageous over other sampling techniques, but is often characterized by insufficient accuracies, particularly at longer sampling times. Experimental investigation of this issue and disclosing the origin of the problem is problematic and often not practically feasible due to high uncertainties. This research is aimed at developing the model of TWA extraction process and optimization of TWA air sampling by SPME using finite element analysis software (COMSOL Multiphysics). It was established that sampling by porous SPME coatings with high affinity to analytes is affected by slow diffusion of analytes inside the coating, an increase of analytes concentrations in the air near the fiber tip due to equilibration, and eventual lower sampling rate. The increase of a fiber retraction depth (Z) resulted in better recoveries. Sampling of studied VOCs using 23-ga Car/PDMS assembly at maximum possible Z (40 mm) was proven to provide more accurate results. Alternative sampling configuration based on 78.5 x 0.75 mm i.d. SPME liner was proven to provide similar accuracy at improved detection limits. Its modification with the decreased internal diameter from the sampling side should provide even better recoveries. The developed model offers new insight into optimization of air and gas sampling using SPME.

scholarly journals Modeling Solid-Phase Microextraction of Volatile Organic Compounds by Porous Coatings Using Finite Element Analysis

2019 ◽  
Author(s):  
Bulat Kenessov ◽  
Miras Derbissalin ◽  
Jacek A. Koziel ◽  
Dmitry S. Kosyakov
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Volatile Organic Compounds ◽  
Mass Transport ◽  
Organic Compounds ◽  
Solid Phase Microextraction ◽  
Solid Phase ◽  
Element Analysis ◽  
Volatile Organic ◽  
Pdms Coating

Experimental optimization of analytical methods based on solid-phase microextraction (SPME) is a complex and labor-intensive process associated with uncertainties. Using theoretical basics of SPME and finite element analysis software for the optimization proved to be an efficient alternative. In this study, an improved finite element analysis-based model for SPME of volatile organic compounds (VOCs) by porous coatings was developed mainly focussing on the mass transport in coatings. Benzene and the Carboxen/polydimethylsiloxane (Car/PDMS) coating were used as the model VOC and a porous SPME coating, respectively. It has been established that in the coating, volumetric fractions of Carboxen, PDMS, and air are 33, 42 and 25%, respectively. It has been proven that Knudsen diffusion in micropores can slow down a mass transport of analytes in the coating. For Car/PDMS coating, mass transport of benzene is mostly characterized by a molecular diffusion, which can be explained by a large fraction of macro- and mesopores. It has been shown that the developed model can be used to model the extraction of VOCs from air and water samples encountered in a typical SPME development method procedure. It was possible to determine system equilibration times and use them to optimize sample volume and Henry’s law constant. The developed model is relatively simple, fast, and can be recommended for optimization of extraction parameters for other analytes and SPME coatings. The diffusivity of analytes in a coating is an important property needed for improved characterization of existing and new SPME polymers and analytical method optimization.

scholarly journals Determination of kinetic parameters for pressed tetranitropentaerytrite according to results of ODTX experiments

2019 ◽  
pp. 57-64
Author(s):  
Y. S. Zuev ◽  
N. I. Karmanov
Keyword(s):  
Experimental Data ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Kinetic Parameters ◽  
Satisfactory Agreement ◽  
Software Package ◽  
Analytical Dependence ◽  
Analysis Software ◽  
Element Analysis

The paper introduces a method for determining kinetic parameters for the pressed explosive tetranitropentaerytrite. This method includes analytical dependence for the period of induction, which is used to process the experimental data, and the ANSYS CFD finite element analysis software package. The found values of the kinetic parameters made it possible to obtain a satisfactory agreement between the calculated and experimental ignition distances for pressed tetranitropentaerytrite

scholarly journals Modeling Solid-Phase Microextraction of Volatile Organic Compounds by Porous Coatings Using Finite Element Analysis

2019 ◽  
Author(s):  
Bulat Kenessov ◽  
Miras Derbissalin ◽  
Jacek A. Koziel ◽  
Dmitry S. Kosyakov
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Volatile Organic Compounds ◽  
Mass Transport ◽  
Organic Compounds ◽  
Solid Phase Microextraction ◽  
Solid Phase ◽  
Element Analysis ◽  
Porous Coatings ◽  
Volatile Organic

Experimental optimization of analytical methods based on solid-phase microextraction (SPME) is a complex and labor-intensive process associated with uncertainties. Using the theoretical basics of SPME and finite element analysis software for the optimization proved to be an efficient alternative. In this study, an improved finite element analysis-based model for SPME of volatile organic compounds (VOCs) by porous coatings was developed mainly focussing on the mass transport in coatings. Benzene and the Carboxen/polydimethylsiloxane (Car/PDMS) coating were used as the model VOC and a porous SPME coating, respectively. It has been established that in the coating, volumetric fractions of Carboxen, PDMS, and air are 33, 42 and 24%, respectively. Knudsen diffusion in micropores can slow down a mass transport of analytes in the coating. When PDMS was considered as the solid part of the coating, lower root-mean-square deviation of the modeling results from experimental data was observed. It has been shown that the developed model can be used to model the extraction of VOCs from air and water samples encountered in a typical SPME development method procedure. It was possible to determine system equilibration times and use them to optimize sample volume and Henry’s law constant. The developed model is relatively simple, fast, and can be recommended for optimization of extraction parameters for other analytes and SPME coatings. The diffusivity of analytes in a coating is an important property needed for improved characterization of existing and new SPME polymers and analytical method optimization.

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