A novel needle trap device with nanoporous silica aerogel packed for sampling and analysis of volatile aldehyde compounds in air

Needle trap device technique: From fabrication to sampling

Needle Trap Device (NTD) as a novel, versatile, and eco-friendly technique has played an important role in analytical and environmental chemistry. The distinctive role of this interdisciplinary technique can be defended through the sampling and analysis of biological samples and industrial pollutants in gaseous and liquid environments. In recent years, significant efforts have been made to enhance the performance of the needle trap device resulting in the development of novel extraction routes by various packing materials with improved selectivity and enhanced adsorption characteristics. These achievements can lead to the facilitated pre-concentration of desired analytes. This review tries to have a comparative and comprehensive survey of the three important areas of NTD technique: I) Fabrication and preparation procedures of NTDs; II) Sampling techniques of pollutants using NTDs; and III) Employed materials as adsorbents in NTDs. In the packing-material section, the commercial and synthetic adsorbents such as carbon materials, metal-organic frameworks, aerogel, and polymers are considered. Furthermore, the limitations and potential areas for future development of the NTD technique are presented.

Determination of Polychlorinated Biphenyls in Water Samples Using a Needle Trap Device Combined with Gas Chromatography

In this study, a fiber-packed needle trap device (NTD) was developed by packing heat-resistant fibers with a polyethylene glycol sol-gel coating into a 21-gauge, stainless steel needle. The polyethylene glycol sol-gel coating has numerous advantages, including uniform roughness and a large specific surface area. The prepared NTD was used for headspace extraction of five polychlorinated biphenyls (PCBs) in water samples, determined by gas chromatography with a flame ionization detector (GC-FID). The main experimental parameters, including the extraction and desorption conditions, ionic strength, and fiber bundles, were investigated to improve the extraction efficiency. After optimization, satisfactory linearity (r > 0.99) in the concentration range of 0.02–500 μg/L was obtained, and the enrichment factor of NTD for the five PCBs was between 1150 and 9537 times. The limit of detection (S/N = 3) of five PCBs were measured in ranges of 0.0021–0.01 μg/L. Furthermore, the fiber-packed NTD has excellent durability, and can be reused for 60 cycles. After being stored at room temperature for three days, the storage ability of the NTD had a loss of PCBs less than 10%, and the relative standard deviation (RSD) was less than 10%. When analyzing the PCBs in real water samples, good accuracies (spiked recoveries were in the range of 92.19–98.56%) and precision (the RSD was lower than 12.8%) was obtained.

Development of a new needle trap-based method for the determination of some volatile organic compounds in the indoor environment

Volatile Organic Compounds (VOCs) are a large group of chemicals mostly found in indoor environments such as homes and workplaces. Long term exposure to certain VOCs can cause symptoms in some individuals and therefore, monitoring and controlling air quality can help better manage chronic respiratory diseases. In this study, we aimed to develop an easy-to-use, economical, in house needle trap-based methodology to detect certain VOCs to be used for public and occupational health. For this purpose, a multi-bed (packed with PDMS/Carbopack-X/Carboxen-1000) needle trap device (NTD) was utilized for sampling, enrichment, and injection of the VOCs into the gas chromatography. The performance of the developed method was investigated for the analysis of the group known as BTEX (benzene, toluene, ethylbenzene and xylene). Operational and instrumental parameters such as sampling flow rate and relative humidity, desorption time and temperature were optimized, and the analytical figures of merit of the proposed method have indicated that very low levels of BTEX in air samples can be easily determined by this new method. Overall results have shown that multi-bed NTD offers a high sensitive procedure for sampling and analysis of BTEX in concentration range of 0.002-0.298 mg/m³ in indoor air.

Recyclable nitrogen-containing chitin-derived carbon microsphere as sorbent for neonicotinoid residues adsorption and analysis

Chitin-derived three-dimensional nanomaterials has tremendous potential in pesticide residue analysis as an attractive green substitute for toxic solvents. The work presented herein focuses on constructing the environmentally friendly nitrogen-containing chitin-derived carbon microspheres (N-CCMP) for the efficient adsorption of neonicotinoid pesticides (NPs) including acetamiprid, clothianidin, imidacloprid and thiamethoxam. The N-CCMP displayed hierarchical porous structure, uniform size distribution, and excellent specific surface area of 680.8 m²  g^-1. The N-CCMP with N-heterocyclic ring structure and surface oxygen functional groups exhibited good affinity to NPs, which was beneficial for the rapid adsorption. Then, the N-CCMP were utilized as sorbent in extraction of NP residues. Under the optimum conditions, the relative recoveries in water and juice sample were in the range of 85 %-116 % and 74 %-108 %, with relative standard deviations (RSDs) of 0.1 %∼5.2 % and 0.7 %∼5.2 %, respectively. The extraction performance of N-CCMP were still over 80 % after 5 times of reuse.

Fan-based device for integrated air sampling and microextraction

In this article, a new air sampler based on a conventional computer fan is presented and evaluated. The fan has a double role as it acts as the air pumping system and supports the sorptive phases, which are located on its blades. The compact design and the reduced energy consumption (it can operate with a standard cell phone charger) confers high portability to the device. Also, a simple alternative integrated into the fan is proposed for using an internal standard during the sampling, thus increasing the precision of the measurements. In this first communication, sol-gel Carbowax 20 M coated fabric phases are used as sorptive membranes thanks to their planar geometry, mechanical and thermal stability, and their versatility covering different interaction chemistries. After sampling, the fabric phases are placed in a headspace vial, which is finally analyzed by gas chromatography-mass spectrometry. The sampler has been characterized for the extraction of selected volatile organic compounds (chloroform, benzaldehyde, toluene, and cyclohexane) from air and its versatility has also been evaluated by the identification of semi-volatile compounds in working place (toluene and xylene in laboratory residue storage room) and biogenic volatile compounds in natural samples (terpenes in fresh pine needles and orange peel samples).

Quantitation of volatile aldehydes using chemoselective response dyes combined with multivariable data analysis

Current work proposed a novel quantitative method of volatile aldehydes (VAs) using chemoselective response dyes (CRDs) combined with multivariate data analysis. Multivariate spectral data of selected CRDs was obtained by visible near-infrared spectroscopy. The Synergy-interval Partial Least Squares (Si-PLS) algorithm processed multivariate spectral data to establish VAs quantitative prediction models at the level of 0.0002 v/v to 0.18 v/v. The prediction coefficient (Rp) values of models ranged from 0.8399 to 0.9886, and the Root Mean Square Error of Prediction (RMSEP) values were less than 0.01. These models were verified by classification of aging rice samples, and 93% samples were correctly identified in prediction set. In addition, Density Functional Theory (DFT) calculations explored the interaction mechanism between selected CRDs and VAs. The optimized Highest Occupied Molecular Orbital-Lowest Unoccupied Molecular Orbital (HOMO-LUMO) energy levels, dipole moment, distance between molecules were found to have strong correlations with the interaction.

Poly(ionic liquid)-hybridized silica aerogel for solid-phase microextraction of polycyclic aromatic hydrocarbons prior to gas chromatography-flame ionization detection

Using poly(ionic liquid) (PIL) and tetraethyl orthosilicate (TEOS) as the co-precursors, PIL-hybridized silica aerogel was prepared via sol-gel method for solid-phase microextraction (SPME). The ratio between PIL and TEOS was regulated to achieve the best extraction effect. The aerogel was coated onto the surface of stainless steel wire to get SPME fiber. Coupled to gas chromatography-flame ionization detector (GC-FID), the fiber was separately evaluated by the determination of alkanes, polycyclic aromatic hydrocarbons (PAHs), as well as BTEX (benzene, toluene, ethylbenzene, and xylenes) in immersion mode. The extraction performance of PAHs was attributed to π stacking and hydrophobic effect. After optimization of main extraction and desorption conditions, the SPME-GC-FID method was established towards eight PAHs, and it provided low detection limits (0.005 μg L^-1, 0.010 μg L^-1) and wide linear ranges (0.016-20.00 μg L^-1, 0.033-20.00 μg L^-1) with good linear coefficients (0.9991-0.9998). The method was applied to detect trace PAHs in real water samples, with relative recoveries of 86.2-119.2%. Furthermore, PIL-hybridized silica aerogel exhibits some superiorities like higher sensitivity, shorter extraction time, and better repeatability over other extraction coatings. The present work not only extends the range of aerogel materials but also promoted their further applications in sample preparation. Graphical abstract.

Miniaturized analytical methods for determination of environmental contaminants of emerging concern - A review

The determination of contaminants of emerging concern (CECs) in environmental samples has become a challenging and critical issue. The present work focuses on miniaturized analytical strategies reported in the literature for the determination of CECs. The first part of the review provides brief overview of CECs whose monitoring in environmental samples is of particular significance, namely personal care products, pharmaceuticals, endocrine disruptors, UV-filters, newly registered pesticides, illicit drugs, disinfection by-products, surfactants, high technology rare earth elements, and engineered nanomaterials. Besides, an overview of downsized sample preparation approaches reported in the literature for the determination of CECs in environmental samples is provided. Particularly, analytical methodologies involving microextraction approaches used for the enrichment of CECs are discussed. Both solid phase- and liquid phase-based microextraction techniques are highlighted devoting special attention to recently reported approaches. Special emphasis is placed on newly developed materials used for extraction purposes in microextraction techniques. In addition, recent contributions involving miniaturized analytical flow techniques for the determination of CECs are discussed. Besides, the strengths, weaknesses, opportunities and threats of point of need and portable devices have been identified and critically compared with chromatographic methods coupled to mass chromatography. Finally, challenging aspects regarding miniaturized analytical methods for determination of CECs are critically discussed.

Estimation of formaldehyde occupational exposure limit based on genetic damage in some Iranian exposed workers using benchmark dose method

The present study evaluated an occupational exposure level for formaldehyde employing benchmark dose (BMD) approach. Dose-response relationship was determined by utilizing cumulative occupational exposure dose and DNA damage. Based on this goal, outcome of comet assay for some Iranian exposed people in occupational exposure individuals was used. In order to assess formaldehyde exposure, 53 occupationally exposed individuals selected from four melamine tableware workshops and 34 unexposed subjects as a control group were examined. The occupational exposure dose was carried out according to the NIOSH-3500 method, and the DNA damage was obtained by employing comet assay in peripheral blood cells. EPA Benchmark Dose Software was employed for calculating BMD and BMDL. Cumulative exposure dose of formaldehyde was between of 2.4 and 1972 mg. According to the findings of the current study, the induction of DNA damage in the exposed persons was increased tail length and tail moment (p < 0.001), when compared to controls. Finally, an acceptable dose-response relationship was obtained in three-category information between formaldehyde cumulative exposure doses and genetic toxicity. BMDL was 0.034 mg/m³ (0.028 ppm), corresponding to genetic damage of peripheral blood cells. It can be concluded that the occupational permissible limit in Iranian people could be at levels lower than OSHA standards.

An organic-inorganic hybrid silica aerogel prepared by co-precursor method for solid-phase microextraction coating

In order to improve the extraction performance of silica aerogel, an organic-inorganic hybrid silica aerogel was developed as the coating of solid-phase microextraction (SPME). It was prepared via the co-precursor reaction between tris(triethoxysilylpropyl)amine and tetraethyl orthosilicate. Coupled with gas chromatography, the hybrid silica aerogel-coated SPME fiber was evaluated using polycyclic aromatic hydrocarbons (PAHs). Compared to silica aerogel, the hybrid silica aerogel displayed better extraction performance, peak areas of PAH analytes were increased by about 2 times. The affecting parameters including extraction time, extraction temperature, ionic strength, stirring rate and desorption time were optimized, and an analytical method was established with wide linear ranges (0.005-20 μg L^-1, 0.010-20 μg L^-1, 0.100-20 μg L^-1), good correlation coefficients (0.9967-0.9994), low limits of detection (0.001-0.030 μg L^-1) and limits of quantitation (0.005-0.100 μg L^-1). Satisfactory extraction repeatability (RSD≤6.1%, n = 3) and preparation repeatability (RSD ≤ 9.8%, n = 3) were also obtained. Compared to the reported coatings and the commercial coating, the organic-inorganic hybrid silica aerogel has higher or comparable sensitivity, better repeatability, and shorter extraction time and longer service life. The established method was used for the detection of lake water and rain water, and some targets were quantified successfully.