Cold Fiber Solid-phase Microextraction Research Articles

Application of poly 3,4-ethylenedioxythiophene and gold nanoparticles composite on a gold wire as a coating for determination of nitroaromatics in soil using cold fiber solid phase microextraction combined with gas chromatography

Although several sensing techniques have been employed for nitroaromatics, developing novel detection approaches for environment analysis is still necessary. In this study, for the first time, the cooling assisted solid phase microextraction (CA-SPME) method was performed using poly 3,4-ethylenedioxythiophene and gold nanoparticles composite coating on a gold wire to extract nitroaromatic compounds. The surface morphology of the homemade SPME fiber was investigated through a field emission scanning electron microscope. The fiber was used to extract 4-nitrotoluene (4-NT), 1,3-dinitrobenzene (1,3-DNB), 2,4-dinitrotoluene (2,4-DNT), and 2,6-dinitrotoluene (2,6-DNT) from the soil. To increase extraction efficiency and reduce interferences, extraction was performed from the sample headspace, and the fiber was cooled by a cooling apparatus. Then, the extracts of nitroaromatics were injected into the gas chromatography- flame ionization detector instrument to identify and quantify the analytes. A set of effective experimental parameters in fiber coating characteristics and extraction and separation procedures, including extraction temperature, extraction time, vial volume, and separation conditions in gas chromatography, were optimized. Under optimal conditions, recoveries of nitroaromatics ranged from 96.80% to 102.10%, and the detection limit values were in the range of 0.15 to 0.30 ng.g−1. The linear ranges were obtained to be 0.5–250.0 ng.g−1 and 1.0–250.0 ng.g−1 for 4-NT, 2,4-DNT, 2,6-DNT, and 1,3-DNB, respectively. Finally, the proposed method was successfully tested on real soil samples.

Determination of Polycyclic Aromatic Hydrocarbons in Eggs Exposed to Fire Using a Simple and Efficient Method

The illicit burn practices on farms promote food contamination that is harmful and must be controlled by improved analytical methods. Polycyclic aromatic hydrocarbons (PAHs), which have high toxic and carcinogenic potential, can contaminate foods, mainly through fire exposure. Considering the toxicity of PAHs, development of sensitive, simple, and solvent-free methods to analyze PAHs in foods is necessary. This work presents the development of a new method to analyze PAHs in eggs using cold fiber-solid-phase microextraction (CF-SPME) and gas chromatography coupled to mass spectrometry (GC-MS). Parameters of temperature extraction, ultrasonic agitation time, sample mass, and modifiers were evaluated to obtain the best CF-SPME conditions. The new method uses a minimal amount of solvent and showed good linearity in the range of 0.0005 to 5.60 μg/g. Detection limits were from 0.0002 to 0.046 μg/g, and quantification limits were from 0.0005 to 0.152 μg/g. The method was applied to PAHs analysis of chicken egg samples from a farm near a site of an uncontrolled tire fire. The concentrations of PAHs in this study ranged from 0.926 to 1.668 μg/g. All PAHs were detected in the samples. The total toxicity was estimated by benzo(a)pyrene equivalent (BaPeq) and did not decrease significantly in the period (6 weeks) of sample collection.

Application of Artificial Neural Network and Response Surface Methodology in Optimization of Cold Fiber Headspace Solid-Phase Microextraction (CF-HS-SPME) for Analysis of 2, 5-Hexandion in Urine Samples

Background: Cold-Fiber Solid-Phase Microextraction (CF-SPME) is often used for the extraction of volatile and semi-volatile compounds from complex matrices. Multivariate statistical optimization techniques can save time and chemicals and thus decrease the analytical cost in comparison with the Single Variable Approach (SVA). Over the past few decades, different beneficial mathematical tools have been developed for the optimization of separation processes. Objectives: In this study, the Artificial Neural Network (ANN) and Response Surface Methodology (RSM) applications were compared for CF-SPME optimization to determine 2, 5-hexandion in urine samples. 2, 5-Hexanedione is a colorless liquid and the main metabolite of n-hexane as a result of occupational exposure. Methods: N-hexane is widely used in the rubber industry, food processing, solvents, and medicinal drugs and has adverse effects such as neurotoxicity on humans. Thus, biological monitoring, analytic methods, and mathematical and statistical techniques concerning 2.5-HD are very important. The RSM and ANN are mathematical and statistical techniques applied for the optimization and process modeling. Designing an experiment based on the Historical Data Design (HDD) of RSM was adopted to evaluate the relationship between independent parameters such as extraction temperature, extraction time, sample volume, and extraction efficiency of 2, 5-hexandion. Results: The models were compared for their predictive ability by the coefficient of determination (R2) and Root Mean Square Error (RSME) based on the train and test dataset. Conclusions: The results were highly significant (P < 0.05) for the optimization of variables. The ANN model had more generalizability than the RSM model. Also, the ANN had higher predictive accuracy.

Phase distribution of polycyclic aromatic hydrocarbons and their oxygenated and nitrated derivatives in the ambient air of a Brazilian urban area☆

Air quality in large cities has worsened in recent years as a consequence people’s health is directly affected. Among the toxic compounds released to environmental air are polycyclic aromatic hydrocarbons (PAHs), nitrated PAHs (nitro-PAHs), and oxygenated PAHs (oxy-PAHs). Performant methods to analyze these compounds is necessary to enable adequate monitoring of air quality. Thus, this manuscript presents the development of a highly sensitive method to analyze PAHs, nitro-PAHs, and oxy-PAHs collected from ambient air (PM2.5) and the gas phase for a period of one year in the urban area of Belo Horizonte, Brazil. PAHs and their derivatives were extracted by cold fiber solid phase microextraction (CF-SPME) and analyzed by gas chromatography coupled to mass spectrometry (GC/MS). The proposed method allows simultaneous analysis of 16 PAHs, nitro-PAHs and oxy-PAHs, presenting very good limits of detection and quantification, as well as appropriate precision and recovery. The results obtained for the period of one year allowed different studies. The compounds collected simultaneously from gas and particulate phase showed that total concentration of 16 PAHs were higher in the gas phase than in the particulate. On the other hand, nitro-PAHs and oxy-PAHs presented similar concentration in gas and particulate phases. The potential carcinogenicity of PAHs relative to benzo[a]pyrene showed benzo[a]pyrene equivalents of 0.49 ng m−3. The estimated risk of lifetime lung cancer was 5 × 10−5. Principal component analysis and diagnostic ratio was applied for source distribution indicating that burning of gasoline, diesel and biomass accounted for the PAHs profile in ambient air samples.

Recent Applications and Newly Developed Strategies of Solid-Phase Microextraction in Contaminant Analysis: Through the Environment to Humans

The present review aims to describe the recent and most impactful applications in pollutant analysis using solid-phase microextraction (SPME) technology in environmental, food, and bio-clinical analysis. The covered papers were published in the last 5 years (2014–2019) thus providing the reader with information about the current state-of-the-art and the future potential directions of the research in pollutant monitoring using SPME. To this end, we revised the studies focused on the investigation of persistent organic pollutants (POPs), pesticides, and emerging pollutants (EPs) including personal care products (PPCPs), in different environmental, food, and bio-clinical matrices. We especially emphasized the role that SPME is having in contaminant surveys following the path that goes from the environment to humans passing through the food web. Besides, this review covers the last technological developments encompassing the use of novel extraction coatings (e.g., metal-organic frameworks, covalent organic frameworks, PDMS-overcoated fiber), geometries (e.g., Arrow-SPME, multiple monolithic fiber-SPME), approaches (e.g., vacuum and cold fiber SPME), and on-site devices. The applications of SPME hyphenated with ambient mass spectrometry have also been described.

Determination of polycyclic aromatic hydrocarbons and their nitrated and oxygenated derivatives in coffee brews using an efficient cold fiber-solid phase microextraction and gas chromatography mass spectrometry method

Polycyclic aromatic hydrocarbons (PAHs) are food contaminants; besides, their oxygenated (oxy-PAHs) and nitrated (nitro-PAHs) derivatives have also been detected in some foods. This is worrying because these derivatives may be more toxic than PAHs. This study presents a new method for the determination of PAHs and their oxygenated and nitrated derivatives in coffee brew. The analytes were extracted by cold fiber solid phase microextraction (CF-SPME) with analysis by gas chromatography/mass spectrometry. The developed method presented good precision with intra-assay and inter-assay, ranged from 4.5 to 16.4%, and from 9.8 to 19.8%, respectively. Recovery ranged from 82.1 to96.3% and linearity showed good adjustment presenting determination coefficients (R2) from 0.980 to 0.999. The limits of quantification ranged from 0.025 to 0.224 μg L−1. The proposed method is simple, versatile, allows simultaneous extraction of PAHs, nitrated and oxygenated derivatives and was successfully applied to the analysis of commercial coffee samples. Benzo(k)fluoranthene, benzo(b)fluoranthene, pyrene, acenaphthylene and acenaphthene are the most abundant PAHs found in samples. In addition, 5,12-naphthacenequinone was the most abundant oxy-PAH and 1-nitropyrene was the most abundant nitro-PAH.

Use of exhaled air as an improved biomonitoring method to assess perchloroethylene short-term exposure

This paper shows the use of exhaled air as a biomonitoring method to assess perchloroethylene (PERC) environmental and occupational exposure. A sensitive, fast, and solvent free analytical method was developed to determine PERC in ambient and exhaled air of individuals occupationally exposed. The developed method used cold fiber solid phase microextraction (CF-SPME) as the sampling technique, and a standard permeation method to simulation of air matrix. The analysis were conducted by gas chromatography coupled to mass spectrometry (GC/MS). The methods were validated and were found to be precise, linear and sensitive for environmental and biological monitoring. The developed methods were applied to twenty-seven sampling points spread across Belo Horizonte city, Brazil, twenty four dry cleaners, an electroplating industry, a research laboratory, and an automotive paint preparation shop. The results of ambient air analyses ranging from 14.0 to 3205.0µgm−3 with median concentration of 599.0µgm−3. Furthermore, sampling of exhaled air of individuals occupationally exposed presented results ranging from 6.0 to 2635.0µgm−3 with median concentration of 325.0µgm−3. The strong correlation observed between ambient and exhaled air (r =0.930) demonstrates that exhaled air is a suitable biomarker for evaluating occupational exposure to PERC.

Environmental and biological determination of acrolein using new cold fiber solid phase microextraction with gas chromatography mass spectrometry.

Acrolein is a pollutant released daily to the indoor environment from different sources. The present study reports the development of a simple and sensitive cold fiber solid phase microextraction sampling method for the determination of acrolein in exhaled air and indoor air by gas chromatography mass spectrometry. O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine was used as derivatizing agent supported on a 65-μm polydimethylsiloxane-divinylbenzene SPME fiber. An acrolein permeation tube at 326.25ngmin-1 rate was used to generate gaseous standards. The method shows good results for main validation parameters. The limits of detection and quantification were 2.88 and 5.08μgm-3, respectively, for indoor analysis; and 2.40 and 3.79μgm-3, respectively, for exhaled air analysis. The precision showed standard deviation ranges from 6.00 to 8.00% for intra-assay analyses and from 8.00 to 10.00% for inter-assay analyses. After optimizing the conditions, analyses of real samples were performed on indoor environments contaminated by cigarette smoke, or heated oil, including pastry shops, restaurants, churros stands, and closed parking cars located in the city of Belo Horizonte, Brazil. Acrolein breaths of exposed people were also determined. A good Pearson correlation coefficient (r = 0.901) was observed between the concentration of acrolein in indoor air and exhaled air, allowing to propose acrolein breath as environmental exposure biomarker. Graphical Abstract Cold fiber solid phase microextraction gas chromatography/mass spectrometry.

Determination of Polycyclic Aromatic Hydrocarbons in Sediment by Pressure-Balanced Cold Fiber Solid Phase Microextraction.

An improved performance of the cold fiber solid phase microextraction (CF-SPME) technique was accomplished with the use of the pressure-balanced procedure. In order to obtain a pressure-balanced state during extraction at 200 °C, 7 mL of air volume was withdrawn from 10 mL commercial vials, while 15 mL was withdrawn from vials where 5 μL of diethylamine was added as a modifier/displacer. The benefits of the balanced system were demonstrated for determination of polycyclic aromatic hydrocarbons (PAHs) from solid matrixes, including sand and certified sediment samples. Results showed the pressure-balanced procedure enhanced the extraction efficiency of the method, especially for high volatility compounds, as the leakage of analytes was mitigated under sample temperature conditions of 200 °C. Analytical precision was also improved, with relative standard deviations (RSDs) ranging from 4% to 8% for all analytes under study. For the determination of PAHs in certified sediment samples, pressure-balanced CF-SPME yielded more accurate results in comparison to nonpressure-balanced CF-SPME. The proposed methodology provided the additional benefit of improved recoveries at lower pressures.

Application of a new fiber coating based on electrochemically reduced graphene oxide for the cold-fiber headspace solid-phase microextraction of tricyclic antidepressants

A new fiber based on the electrochemical reduction of graphene oxide was prepared on a copper wire for solid-phase microextraction (SPME) applications. The prepared fiber was used for the SPME and gas chromatographic analysis of tricyclic antidepressants (TCADs), including amitriptyline, trimipramine, and clomipramine. The feasibility of direct-immersion and headspace modes of SPME for the determination of TCADs was studied. The effects of four parameters including pH, salt content, extraction temperature with and without cooling the fiber, and extraction time were investigated. The comparison showed that headspace cold fiber SPME results in the best outcome for the extraction of TCADs. Under the optimized conditions of this mode, the calibration curves were linear between 2.0 and 500 ng/mL and the detection limits were between 0.30 and 0.53 ng/mL. The intraday and interday RSDs obtained at 20 ng/mL (n = 5), using a single fiber, were 5.5-9.0 and 7.5-9.8, respectively. The fiber to fiber repeatability (n = 4), expressed as the RSD, was between 12.8 and 13.2% at a 20 ng/mL concentration level. The method was successfully applied to the analysis of TCADs in plasma samples showing recoveries from 73 to 96%.

A sensitive GC/MS method using cold fiber SPME to determine polycyclic aromatic hydrocarbons in spring water

Polycyclic aromatic hydrocarbons (PAH) are carcinogenic to humans and can be found in various environments. This paper describes a cold fiber (CF) solid-phase microextraction (SPME) sampling method with gas chromatography mass spectrometry (GC/MS) to identify 16 PAH in spring water. The method yields good results for some validation parameters. The LOD and LOQ ranged from 7.10 to 57.96ngL−1 and from 23.60 to 193.19ngL−1, respectively. The intra-assay precision shows a coefficient of variation (CV) ranging from 4.38 to 17.65%, and recovery tests varied from 76±13% to 99±8%. The proposed method was attractive, as it extracted higher amounts of PAH in a single extraction procedure in comparison with conventional approaches. The method was applied to the analyses of PAH in twenty-four spring water samples collected in Divinópolis City, Minas Gerais, Brazil. Average PAH concentrations were in the range of 62.80±10.40ngL−1 for Benzo[a]anthracene and 146.58±98.98ngL−1 for Benzo[a]pyrene.

New method to determination of naphthalene in ambient air using cold fiber-solid phase microextraction and gas chromatography–mass spectrometry

Naphthalene, a highly volatile polycyclic aromatic hydrocarbon (PAH), is classified as possibly carcinogenic to humans and can be found in various environments. This paper describes a cold fiber (CF) solid phase microextraction (SPME) sampling method coupled with gas chromatography/mass spectrometry (GC/MS) for determining naphthalene in ambient air. The method uses a 100μm polydimethylsiloxane (PDMS) fiber to generate gaseous standards using a permeation tube. The method shows good results for many validation parameters. The intra-assay precision shows a relative standard deviation (RSD) ranging from 1.04 to 8.11%; the limit of detection (LOD) is 0.33±0.01μg/m3, and the quantification limit (LOQ) is 0.55±0.01μg/m3. The method was applied to the determination of naphthalene from real samples collected from indoor and outdoor air. The results have shown the ability of the method to measure trace levels of naphthalene in the air in different environments.

Evaluation of a completely automated cold fiber device using compounds with varying volatility and polarity

A fully automated cold fiber solid phase microextraction device has been developed by coupling to a GERSTEL multipurpose (MPS 2) autosampler and applied to the analysis of volatiles and semi-volatiles in aqueous and solid matrices. The proposed device was thoroughly evaluated for its extraction performance, robustness, reproducibility and reliability by gas chromatograph/mass spectrometer (GC/MS). With the use of a septumless head injector, the entire automated setup was capable of analyzing over 200 samples without any GC injector leakages. Evaluation of the automated cold fiber device was carried out using a group of compounds characterized by different volatilities and polarities. Extraction efficiency as well as analytical figures of merit was compared to commercial solid phase microextraction fibers. The automated cold fiber device showed significantly improved extraction efficiency compared to the commercial polydimethylsiloxane (PDMS) and cold fiber without cooling for the analysis of aqueous standard samples due to the low temperature of the coating. Comparing results obtained from cold fiber and commercial divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber temperature profile demonstrated that the temperature gap between the sample matrix and the coating improved the distribution coefficient and therefore the extraction amount. The linear dynamic range of the cold fiber device was 0.5ngmL−1 to 100ngmL−1 with a linear regression coefficient ≥0.9963 for all compounds. The limit of detection for all analytes ranged from 1.0ngmL−1 to 9.4ngmL−1. The newly automated cold fiber device presents a platform for headspace analysis of volatiles and semi-volatiles for large number of samples with improved throughput and sensitivity.

A new approach based on a combination of direct and headspace cold-fiber solid-phase microextraction modes in the same procedure for the determination of polycyclic aromatic hydrocarbons and phthalate esters in soil samples

This study describes a new approach to cold-fiber solid-phase microextraction (CF-SPME) based on a combination of different extraction modes in the same extraction procedure. Also, the high quantity of water required to facilitate both the desorption of analytes from the matrix and their transport to the fiber coating is reported. The extraction mode was changed from the direct to the headspace mode in a single extraction while manipulating the extraction times and coating temperature to improve the extraction of compounds with different volatilities. Compounds with low volatility were better extracted in the direct mode, while the headspace mode was more appropriate for volatile compounds. Polycyclic aromatic hydrocarbons (PAHs) and phthalic acid esters (PEs) in sand or soil samples were used as model compounds and matrices in this study. The optimized conditions were: sample pH in the range of 4–7, addition of 12 mL of 194 g L −1 aqueous NaCl solution in a 15 mL vial, and 80 min total extraction time with a sample temperature of 90 °C (50 min in direct mode with coating at 90 °C followed by 30 min in headspace mode with coating at 30 °C). The proposed procedure was compared with conventional CF-SPME (with and without addition of water) and was found to be more effective for all the analytes, since it is capable of extracting both heavier and lighter compounds from soil samples in a single extraction procedure. The use of an excess of water and a combination of extraction modes in the same CF-SPME procedure are the main factors responsible for this enhancement. The proposed method was applied to the extraction of PAHs and PEs in spiked soil samples and excellent results were obtained for most of the compounds evaluated.

Cold fiber solid-phase microextraction device based on thermoelectric cooling of metal fiber

A new cold fiber solid-phase microextraction device was designed and constructed based on thermoelectric cooling. A three-stage thermoelectric cooler (TEC) was used for cooling a copper rod coated with a poly(dimethylsiloxane) (PDMS) hollow fiber, which served as the solid-phase microextraction (SPME) fiber. The copper rod was mounted on a commercial SPME plunger and exposed to the cold surface of the TEC, which was enclosed in a small aluminum box. A heat sink and a fan were used to dissipate the generated heat at the hot side of the TEC. By applying an appropriate dc voltage to the TEC, the upper part of the copper rod, which was in contact to the cold side of the TEC, was cooled and the hollow fiber reached a lower temperature through heat transfer. A thermocouple was embedded in the cold side of the TEC for indirect measurement of the fiber temperature. The device was applied in quantitative analysis of off-flavors in a rice sample. Hexanal, nonanal, and undecanal were chosen as three off-flavors in rice. They were identified according to their retention times and analyzed by GC–flame ionization detection instrument. Headspace extraction conditions (i.e., temperature and time) were optimized. Standard addition calibration graphs were obtained at the optimized conditions and the concentrations of the three analytes were calculated. The concentration of hexanal was also measured using a conventional solvent extraction method (697 ± 143 ng/g) which was comparable to that obtained from the cold fiber SPME method (644 ± 8). Moreover, the cold fiber SPME resulted in better reproducibility and shorter analysis time. Cold fiber SPME with TEC device can also be used as a portable device for field sampling.