Determination Of BTEX Compounds Research Articles

Comparison of Air-Assisted, Vortex-Assisted and Ultrasound-Assisted Dispersive Liquid–Liquid Microextraction for the Determination of BTEX Compounds in Water Samples Prior to GC-FID Analysis

Three new dispersive liquid–liquid microextraction (DLLME) methods, air-assisted (AA-DLLME), vortex-assisted (VA-DLLME) and ultrasound-assisted (UA-DLLME), were compared from the point of view of their analytical application for preconcentration of trace amounts of benzene, toluene, ethylbenzene and xylene isomers (BTEX) in water samples. In all of these methods, no dispersive solvent is required and dispersion of extractant is carried out by air bubbles, vortex and ultrasound for AA-DLLEM, VA-DLLME, and UA-DLLME, respectively. Advantages and disadvantages of these three liquid phase microextraction methods and their capability in dispersion of a similar extractant phase in sample solutions were comprehensively compared. All other extraction parameters, which have an influence on the microextraction, were also investigated and optimized. Under optimized conditions, analytical figures of merit for the three techniques were determined and compared. It was found that the limit of detection of the three methods is almost the same, while AA-DLLME has a wider linear dynamic range and the shortest analysis time. Enrichment factors of 182, 45 and 245 were achieved for AA-DLLEM, VA-DLLME, and UA-DLLME, respectively.

New insight on biological interaction analysis: new nanocrystalline mixed metal oxide SPME fiber for GC-FID analysis of BTEX and its application in human hemoglobin-benzene interaction studies.

Nanocrystalline mixed metal oxides (MMO) of various metal cations were synthesized and were used for coating a piece of copper wire as a new high sensitive solid phase micro extraction (SPME) fiber in extraction and determination of BTEX compounds from the headspace of aqueous samples prior to GC-FID analysis. Under optimum extraction conditions, the proposed fiber exhibited low detection limits, and quantification limits, good reproducibility, simple and fast preparation method, high fiber capacity and high thermal and mechanical durability. These are some of the most important advantages of the new fiber. The proposed fiber was used for human hemoglobin upon interaction with benzene. Binding isotherm, Scatchard and Klotz logarithmic plots were constructed using HS-SPME-GC data, accurately. The obtained binding isotherm analyzed using Hill method. The Hill parameters have been obtained by calculating saturation parameter from the ratio of measured chromatographic peak areas in the presence and absence of hemoglobin. In this interaction, Hill coefficient and Hill constant determined as (nH = 6.14 and log KH = 6.47) respectively. These results reveal the cooperativity of hemoglobin upon interaction with benzene.

Modified SBA-15 mesoporous silica as a novel fiber coating in solid-phase microextraction and determination of BTEX compounds in water samples using gas chromatography-flame ionization detection

Nanoporous silica (SBA-15) was prepared, functionalized with 3-(2-aminoethylamino) propyltrimethoxysilane and employed as a novel solid-phase microextraction (SPME) fiber. The prepared nanoporous silica was immobilized onto a copper wire for fabrication of the SPME fiber. The efficiency and reliability of the prepared device was investigated for the extraction of some volatile organic compound such as benzene, toluene, ethylbenzene and xylenes from the headspace of sample solutions. Five experimental parameters consisting of adsorption temperature, adsorption time, stirring rate, salt concentration and headspace volume were evaluated and optimized by using a Taguchi's L16 (45) orthogonal array experimental design. Under the optimized conditions for all BTEX compounds, the repeatability for one fiber (n = 4), expressed as relative standard deviation was between 5.2 and 9.8% and the reproducibility for four fibers was between 6.83% and 10.9%, the linearity was from 1.5 to 950 μg L−1 and the limit of detection was between 0.15 and 0.42 μg L−1. The recovery values were 83.7 to 108.2% for water samples. The proposed method was applied in the determination of the trace level compounds in natural water samples.

Novel cationic surfactant ion pair based solid phase microextraction fiber for nano-level analysis of BTEX

Ion pair of cationic surfactant (cetytrimethylammonium bromide) and tungestosilicic acid incorporated in PVC matrix, was used for coating a piece of copper wire as a new high sensitive SPME fiber in extraction and determination of BTEX compounds from the headspace of water samples prior to GC/FID analysis. Under optimum extraction conditions, limits of detection for benzene, toluene, ethylbenzene, p-xylene, m-xylene and o-xylene were found to be 1.18, 5.61, 0.87, 0.29, 0.22 and 0.33ngL−1 respectively. Low detection limits, wide linear dynamic ranges, good reproducibility (RSD% 1.48–4.27), high fiber capacity and high mechanical durability are some of the most important advantages of the new fiber.

Determination of BTEX Compounds by Dispersive Liquid–Liquid Microextraction with GC–FID

Rapid, inexpensive, and efficient sample-preparation by dispersive liquid–liquid microextraction (DLLME) then gas chromatography with flame ionization detection (GC–FID) have been used for extraction and analysis of BTEX compounds (benzene, toluene, ethylbenzene, and xylenes) in water samples. In this extraction method, a mixture of 25.0 μL carbon disulfide (extraction solvent) and 1.00 mL acetonitrile (disperser solvent) is rapidly injected, by means of a syringe, into a 5.00-mL water sample in a conical test tube. A cloudy solution is formed by dispersion of fine droplets of carbon disulfide in the sample solution. During subsequent centrifugation (5,000 rpm for 2.0 min) the fine droplets of carbon disulfide settle at the bottom of the tube. The effect of several conditions (type and volume of disperser solvent, type of extraction solvent, extraction time, etc.) on the performance of the sample-preparation step was carefully evaluated. Under the optimum conditions the enrichment factors and extraction recoveries were high, and ranged from 122–311 to 24.5–66.7%, respectively. A good linear range (0.2–100 μg L−1, i.e., three orders of magnitude; r2 = 0.9991–0.9999) and good limits of detection (0.1–0.2 μg L−1) were obtained for most of the analytes. Relative standard deviations (RSD, %) for analysis of 5.0 μg L−1 BTEX compounds in water were in the range 0.9–6.4% (n = 5). Relative recovery from well and wastewater at spiked levels of 5.0 μg L−1 was 89–101% and 76–98%, respectively. Finally, the method was successfully used for preconcentration and analysis of BTEX compounds in different real water samples.

Determination of BTEX Compounds in Solid–Liquid Mixing Paint Using the Combination of Solid Phase Extraction, Thermal Desorption and GC-FID

A novel method was developed and validated for determination of benzene, toluene, p-xylene, m-xylene, o-xylene (BTEX) in a solid–liquid mixing matrix. It makes use of solid phase extraction and thermal desorption (SPE-TD), followed by gas chromatographic flame ionization detector analysis (GC-FID). The trapped BTEX can be measured directly after thermal desorption onto the stainless-steel packed chromatographic column. The effect of tailing area of solvent was removed with the use of SPE-TD technique, and the result shows good reproducibility with very little matrix dependency. The study also supports that the lifetime of the Tenax adsorption tube could be extended over 150 desorption operation at 200 °C, which enables performing excellent stability and reproducibility of BTEX analysis.

Desorption of BTEX from activated charcoal using accelerated solvent extraction: evaluation of occupational exposures

A procedure for the determination of benzene, toluene, ethylbenzene and o-xylene, m-xylene and p-xylene (BTEX) in occupational environments is proposed. These compounds are extracted from activated charcoal using accelerated solvent extraction. Operational parameters are optimized and quantitative recovery is obtained using acetonitrile as the extraction solvent and 1-mL extraction cells, a preheat time of 2 min, a temperature of 160 degrees C, a pressure of 1,500 psi, a static period of 5 min, a flush volume of 110%, two cycles and a purge time of 90 s. Determination of BTEX compounds is carried out by gas chromatography using a flame ionization detector. The recoveries, obtained for a confidence level of 95%, are 91 +/- 4, 100 +/- 3, 104 +/- 2, 93 +/- 4, 99 +/- 2 and 99 +/- 2% for benzene, toluene, ethylbenzene, o-xylene, m-xylene and p-xylene, respectively. The detection limits are 0.5 microg for benzene, 0.7 microg for toluene and 1.0 microg for the other compounds. The proposed procedure has been applied to real samples collected in several workplaces, like a microbiology laboratory, an analytical chemistry laboratory, a printer's, a car repair shop and a petrol station. From the results obtained, it can be concluded that the occupational exposures determined are always acceptable because they are lower than the tenth part of the recommended exposure limits (VLA-ED and VLA-EC).

Determination of BTEX Compounds in Water by Solid-Phase Microextraction and Raman Spectroscopy

A new method is described for determining benzene, toluene, ethylbenzene, and xylenes (BTEX) in water that combines solid-phase microextraction and spontaneous Raman spectroscopy. In this method, the BTEX analytes are extracted from the water solution into a solid phase before direct detection by Raman spectroscopy. The solid phase consists of a small volume (ca. 55 μL) of poly(dimethylsiloxane) itch has optical windows in the 750-1300- and 1410-2800-cm -1 Raman shift regions. The time required for each BTEX compound to reach equilibrium between the solid phase and the aqueous phase is in the rye of 16-30 min and affords preconcentration enhancements of 2-3 orders of magnitude. Limits of detection using the most intense Raman bands are in the 1-4-ppm range and produce relative standard deviations of 3-9%. Preliminary application of this new method to the detection of BTEX compounds in real-world water samples shows no significant interferences from river and well water matrices