Development of needle trap technology for on-site determinations: active and passive sampling

An amide-based covalent organic framework chemically anchored on silica nanoparticles for headspace microextraction sampling of halogenated hydrocarbons in air

A needle trap device (NTD) was developed using an amide-based covalent-organic framework (COF), chemically bonded to silica nanoparticles. The NTD was coupled with gas chromatography-flame ionization detection (GC-FID) and employed for the headspace microextraction analysis of halogenated hydrocarbons (HHCs) in the air. The adsorbent was characterized using Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), and field-emission scanning electron microscopy (FE-SEM) techniques. Optimal values for the experimental variables were assessed using response surface methodology (RSM) with a central composite design (CCD), thereby reducing the number of experiments, material consumption, costs, and time. The optimal values for desorption time and temperature were obtained 5 min and 260 °C, respectively. Breakthrough volume (BtV) was studied over the range of 0.5 - 3 times the occupational exposure limit (OEL) and its optimal value was found to be 1200 mL. The optimal sampling temperature and relative humidity (RH) were obtained 20 °C, and 15 %, respectively. The limits of detection (LODs) and limits of quantification (LOQs) were ranged from 0.013 to 0.077 μg l-1 and 0.041 to 0.21 μg l-1, respectively, with a linear dynamic range (LDR) of 0.04 to 100 μg l-1. The method's repeatability and reproducibility (RSD %) were observed over the ranges of 5.3 - 6.4 % and 4.7 -6.9 %, respectively. A statistically validated agreement was observed between the NTD-GC-FID method and the NIOSH 1003 standard procedure for the sampling and determination of HHCs in real workplace air samples, demonstrating the reliability and accuracy of the developed approach.

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.

On-site extraction of benzophenones from swimming pool water using hybrid tapes based on the integration of hydrophilic-lipophilic balance microparticles and an outer magnetic nanometric domain

An on-site extraction device is presented consisting of scotch tape modified with concentric domains of micrometric hydrophilic-lipophilic balance (HLB) particles surrounded by a ring of nanometric magnetic ones. On the one hand, HLB microparticles are readily available at the surface of the tape, exposed to interact with the target analytes, being responsible for the extraction capacity of the sorptive phase. On the other hand, the presence of magnetic nanoparticles enables the attachment of the modified tape onto a metallic screw via a magnet, which is then coupled to a wireless drill, enabling the stirring of the microextraction device. Both are simply fixed to the cost-effective, flexible, and versatile support, i.e., scotch tape, owing to their adhesive properties. The microextraction device has been applied to the determination of six benzophenones in swimming pool water samples. The variables that may affect the extraction process have been evaluated. Under the optimum conditions and using liquid chromatography-tandem mass spectrometry as the instrumental technique, the method provided a limit of detection of 0.03 µg L-1. The intra-day precision, evaluated at three different concentration levels and expressed as relative standard deviation, was lower than 10%, which also comprises the variability within single-use sorptive tapes. The accuracy, calculated with spiked samples and expressed as relative recovery, ranged from 71 to 138%. The method was applied to the analysis of swimming pool water, revealing the presence of such compounds.

Investigation of organophosphorus (OPs) compounds by a needle trap device based on mesoporous organo-layered double hydroxide (organo-LDH)

Organophosphorus (OPs) compounds can endanger human health and the environment by inhibiting the acetylcholinesterase enzyme. But these compounds have been widely used as pesticides due to their effectiveness against all kinds of pests. In this study, a Needle Trap Device (NTD) packed with mesoporous organo-layered double hydroxide (organo-LDH) material and coupled with gas chromatography-mass spectrometry (GC-MS) was employed for the sampling and analysis of OPs compounds (diazinon, ethion, malathion, parathion, and fenitrothion). In this way, the [magnesium-zinc-aluminum] layered double hydroxide ([Mg-Zn-Al] LDH) modified with sodium dodecyl sulfate (SDS) as a surfactant was prepared and characterized by FT-IR, XRD, BET, and FE-SEM, EDS, and elemental mapping techniques. Then, various parameters such as relative humidity, sampling temperature, desorption time, and desorption temperature were evaluated by the mesoporous organo-LDH:NTD method. The optimal values of these parameters were determined using response surface methodology (RMS) and central composite design (CCD). The optimal temperature and relative humidity values were obtained as 20 °C and 25.0%, respectively. On the other hand, the desorption temperature and time values were in the range of 245.0-254.0 °C and 5 min, respectively. The limit of detection (LOD) and limit of quantification (LOQ) were reported in the range of 0.02-0.05 mg m^-3 and 0.09-0.18 mg m^-3, respectively, which shows the high sensitivity of the proposed method compared to the usual methods. The repeatability and reproducibility of the proposed method (by calculating the relative standard deviation) was estimated in the range of 3.8-10.10 which indicates the acceptable precision of the organo-LDH:NTD method. Also, the desorption rate of the stored needles at 25 °C and 4 °C, was determined to be 86.0% and 96.0%, respectively after 6 days. The results of this study proved that the mesoporous organo-LDH:NTD method can be utilized as a fast, simple, environmentally friendly, and effective method for sampling and determining OPs compounds in the air.

Application of a needle trap device packed with a MIP@MOF nano-composite for efficient sampling and determination of airborne diazinon pesticide

In this research, a novel, selective, and efficient porous adsorbent nano-composite comprising a molecularly imprinted polymer and a metal-organic framework (MIP@MOF) was employed for sampling, extraction and analysis of diazinon from the air by a needle trap device (NTD), for the first time. The synthesized MIP@MOF sorbent was characterized by the FT-IR, XRD, FE-SEM, TEM, and EDS techniques. Then, the effective parameters of the sampling (temperature and humidity) and desorption (time and temperature) process were optimized by response surface methodology (RSM). The optimum values of temperature and humidity of the sampling chamber were estimated to be 20 °C and 25.0%, respectively. Also, the highest response during the analyte desorption was obtained at 262 °C and 4.5 minutes. For more details, the performance of the MIP@MOF:NTD method was evaluated by determination of important parameters such as repeatability, reproducibility, the limit of detection (LOD), and the limit of quantification (LOQ), and then compared with the NIOSH 5600 standard method. The values of LOD and LOQ for the targeted analyte were determined to be 0.02 and 0.1 μg m-3, respectively. Also, the repeatability and reproducibility of the proposed method were obtained in the range of (3.9-5.1)% and (5.1-6.4)%, respectively, which proved the acceptable precision of the method. Furthermore, the results of this study exhibited a high correlation coefficient (R 2 = 0.9781) between the proposed method and the recommended NIOSH method. Finally, the proposed procedure was utilized for sampling and determination of the airborne diazinon in real conditions. These results indicated that the proposed MIP@MOF:NTD method can be employed as a fast, simple, environmentally friendly, selective, and effective procedure for sampling and determining diazinon in air.

Needle-Trap Device Containing a Filter: A Novel Device for Aerosol Studies

Particles in an aerosol sample contain a portion of the total available analytes. Therefore, particle trapping is required to fully characterize a gaseous sample. Needle-trap devices (NTDs) are highly useful to this end, as they allow sampling and preconcentration of free analytes, as well as the trapping of particles. Packing sorbents into the needle creates a filter that traps solid particles or liquid droplets. However, the particle-trapping efficiency of sorbent-packed NTDs is limited, especially for nanoparticles. To address this issue, an aerogel based on electrospun polyacrylonitrile (PAN) was prepared for trapping small particles to analyze particle-bound analytes. The PAN aerogel filter was fabricated by cutting electrospun PAN fibers and removing the remaining solvent via freeze-drying to obtain a light porous fibrous structure. The PAN aerogel was heated (H-PAN) prior to packing to ensure stability during thermal desorption. The trapping efficiency of the H-PAN-packed NTD was measured using a range of conditions, with high filtration efficiencies (>99%) being obtained in all cases. The mechanical stability of the H-PAN aerogel was tested using multiple extraction/desorption cycles with and without solid sorbent particles, with results indicating high repeatability (n = 94, relative standard deviation (RSD) <6%). The developed NTD was compared to thin-film microextraction with respect to their ability to characterize breath samples obtained with or without face masks; the NTD was able to trap both free and droplet-bound analytes, while thin-film microextraction was only able to extract free analytes, which is fully reflected in concentrations obtained with these two methods.

An Improvement of SPME-Based Sampling Technique to Collect Volatile Organic Compounds from Quercus ilex at the Environmental Level

Biogenic Volatile Organic Compounds (BVOCs) include many chemical compounds emitted by plants into the atmosphere. These compounds have a great effect on biosphere-atmosphere interactions and may affect the concentration of atmospheric pollutants, with further consequences on human health and forest ecosystems. Novel methods to measure and determine BVOCs in the atmosphere are of compelling importance considering the ongoing climate changes. In this study, we developed a fast and easy-to-handle analytical methodology to sample these compounds in field experiments using solid-phase microextraction (SPME) fibers at the atmospheric level. An improvement of BVOCs adsorption from SPME fibers was obtained by coupling the fibers with fans to create a dynamic sampling system. This innovative technique was tested sampling Q. ilex BVOCs in field conditions in comparison with the conventional static SPME sampling technique. The results showed a great potential of this dynamic sampling system to collect BVOCs at the atmosphere level, improving the efficiency and sensitivity of SPME fibers. Indeed, our novel device was able to reduce the sampling time, increase the amount of BVOCs collected through the fibers and add information regarding the emissions of these compounds at the environmental level.

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).

A needle trap device method for sampling and analysis of semi-volatile organic compounds in air

Semi-volatile organic compounds (SVOCs), such as phthalates, organophosphates, and polybrominated diphenyl ethers, are emerging as an important class of pollutants that are of serious health concerns. Determining concentrations of these pollutants is of great importance for environmental and exposure studies. In this work, a needle trap device (NTD) method was developed to measure the concentration of SVOCs in air samples. Sorbents were packed in the NTD to capture SVOCs with the aid of a sampling pump. NTD operational parameters, such as desorption temperature, desorption time, and sampling flow rate, were optimized for the target SVOCs. The limit of detection for air sampling by the NTD method ranged between 5 pg and 1 ng, depending on the SVOC compound. The variations in terms of NTD repeatability and reproducibility were lower than 14% for all cases. In addition, the influence of other experimental parameters, such as sampling temperature and humidity, breakthrough volume, NTD storage time, as well as carryover effect were examined. Finally, NTDs were used to determine emissions of gas-phase SVOCs from various consumer products in an emission cell and to collect total airborne SVOC samples (gas and particle phases) in an office. The results of NTD method were in an agreement with data obtained by conventional active sampling methods using Tenax® sorbent tubes and polyurethane foam samplers, but with improvements of relative standard deviation, sensitivity, and sampling time. The results demonstrated that the NTD method is a simple, sensitive, effective, reusable, and inexpensive technique for sampling and analyzing SVOCs in the concentration range from 2 ng m^-3 to 100 μg m^-3 in air.

Opportunities for green microextractions in comprehensive two-dimensional gas chromatography / mass spectrometry-based metabolomics - A review

Microextractions have become an attractive class of techniques for metabolomics. The most popular technique is solid-phase microextraction that revolutionized the field of modern sample preparation in the early nineties. Ever since this milestone, microextractions have taken on many principles and formats comprising droplets, fibers, membranes, needles, and blades. Sampling devices may be customized to impart exhaustive or equilibrium-based characteristics to the extraction method. Equilibrium-based approaches may rely on additional methods for calibration, such as diffusion-based or on-fiber kinetic calibration to improve bioanalysis. In addition, microextraction-based methods may enable minimally invasive sampling protocols and measure the average free concentration of analytes in heterogeneous multiphasic biological systems. On-fiber derivatization has evidenced new opportunities for targeted and untargeted analysis in metabolomics. All these advantages have highlighted the potential of microextraction techniques for in vivo and on-site sampling and sample preparation, while many opportunities are still available for laboratory protocols. In this review, we outline and discuss some of the most recent applications using microextractions techniques for comprehensive two-dimensional gas chromatography-based metabolomics, including potential research opportunities.

In-syringe solid-phase extraction for on-site sampling of pyrethroids in environmental water samples

On-site sampling is an analytical approach that can ensure the accuracy of monitoring data and enhance the effectiveness of environmental protection measures. In the present work, an in-syringe solid-phase extraction (SPE) device was designed for on-site sampling of trace contaminants in environmental water samples followed by gas chromatography-mass spectrometry (GC-MS) analysis. Template assisted freeze casting followed by hydrazine vapor reduction approach was used to synthesize a hierarchical porous graphene aerogel (HPGA), which was used as the sorbent in the in-syringe SPE device. Environmental degradable pyrethroids were selected as the model analytes. Owing to the large specific surface area and hydrophobicity of HPGA, the target molecules could be completely extracted during one aspirating/dispensing cycle. The analytes were stable on the sorbent for at least 72 h when the device was stored under airtight and light-free conditions, and were not affected by the pH value of sample solution. All results demonstrated that the device could meet the requirements of on-site sampling. For practical application, the limits of detection were found to be in the range of 0.012-0.11 ng mL^-1 under the optimized conditions, and satisfactory recoveries in the range of 65.7-105.9% were obtained for the analysis of real samples. The results of this study demonstrate the immense potential of HPGA for the enrichment of trace environmental pollutants, and meanwhile promote the application of the in-syringe SPE technique as a promising candidate for on-site sampling.

The role of algae and cyanobacteria in the production and release of odorants in water

This review covers literatures pertaining to algal and cyanobacterial odor problems that have been published over the last five decades. Proper evaluation of algal and cyanobacterial odors may help establish removal strategies for hazardous metabolites while enhancing the recyclability of water. A bloom of microalgae is a sign of an anthropogenic disturbance in aquatic systems and can lead to diverse changes in ecosystems along with increased production of odorants. In general, because algal and cyanobacterial odors vary in chemistry and intensity according to blooming pattern, it is necessary to learn more about the related factors and processes (e.g., changes due to differences in taxa). This necessitates systematic and transdisciplinary approaches that require the cooperation of chemists, biologists, engineers, and policy makers.

Towards on-site analysis of complex matrices by solid-phase microextraction-transmission mode coupled to a portable mass spectrometer via direct analysis in real time

On-site analysis of complex matrices by SPME-TM coupled to a portable mass spectrometer via DART.

Evaluation of a multi-fiber exchange solid-phase microextraction system and its application to on-site sampling

Until recently, multiple solid-phase microextraction fibers could not be automatically desorbed in a single gas chromatographic sequence without manual intervention from an operator. This drawback had been a critical issue, particularly during the analysis of numerous on-site samples taken with various fiber assemblies. Recently, a Multi-Fiber Exchange system, designed to overcome this flaw found in other commercially available autosamplers, was released. In the current research, a critical evaluation of the Multi-Fiber Exchange system performance in terms of storage stability and long-term operation is presented. It was established in the course of our research that the Multi-Fiber Exchange system can operate continuously and precisely for multiple extraction/injection cycles. However, when the effect of residence time of commercial fibers on the Multi-Fiber Exchange tray was evaluated, results showed that among the evaluated fiber coatings, Carboxen/polydimethylsiloxane was the only coating capable of efficient storage on the tray for up to 24 h after field sampling without suffering significant loss of analytes (≤10% for benzene, toluene, ethylbenzene, o-xylene, decane, and limonene). Additionally, the system capability for high-throughput analysis was demonstrated by the unattended desorption of multiple fibers after on-site sampling of toluene, indoor air levels, in a polymer synthesis lab.

In-field Volatile Analysis Employing a Hand-held Portable GC-MS: Emission Profiles Differentiate Damaged and Undamaged Yellow Starthistle Flower Heads

INTRODUCTION

Understanding the complex chemical signalling of plants and insects is an important component of chemical ecology. Accordingly, the collection and analysis of chemical cues from plants in their natural environment is integral to elucidation of plant-insect communications. Remote plant locations and the need for a large number of replicates make in situ headspace analyses a daunting logistical challenge. A hand-held, portable GC-MS system was used to discriminate between damaged and undamaged Centaurea solstitialis (yellow starthistle) flower heads in both a potted-plant and natural setting.

OBJECTIVE

To determine if a portable GC-MS system was capable of distinguishing between undamaged and mechanically damaged plant treatments, and plant environments.

METHODOLOGY

A portable GC-MS utilising needle trap adsorbent technology was used to collect and analyse in situ headspace volatiles of varying yellow starthistle treatments. Principal component analysis (PCA) was used to distinguish treatments and identify biomarker volatiles. Analysis of variance (ANOVA) was used to determine differences between treatment volatile amounts.

RESULTS

The portable GC-MS system detected 31 volatiles from the four treatments. Each GC-MS run was completed in less than 3 min. PCA showed four distinct clusters representing the four treatments - damaged and undamaged potted plant, and damaged and undamaged natural plant. Damage-specific volatiles were identified.

CONCLUSION

The portable GC-MS system distinguished the treatments based on their detected volatile profiles. Additional statistical analysis identified five possible biomarker volatiles for the treatments, among them cyclosativene and copaene, which indicated damaged flower heads.