Single-use porous thin film extraction with gas chromatography atmospheric pressure chemical ionization tandem mass spectrometry for high-throughput analysis of 16 PAHs

Recent Developments in the Detection of Organic Contaminants Using Molecularly Imprinted Polymers Combined with Various Analytical Techniques

Molecularly imprinted polymers (MIPs) encompass a diverse array of polymeric matrices that exhibit the unique capacity to selectively identify a designated template molecule through specific chemical moieties. Thanks to their pivotal attributes, including exceptional selectivity, extended shelf stability, and other distinct characteristics, this class of compounds has garnered interest in the development of highly responsive sensor systems. As a result, the incorporation of MIPs in crafting distinctive sensors and analytical procedures tailored for specific analytes across various domains has increasingly become a common practice within contemporary analytical chemistry. Furthermore, the range of polymers amenable to MIP formulation significantly influences the potential utilization of both conventional and innovative analytical methodologies. This versatility expands the array of possibilities in which MIP-based sensing can be employed in recognition systems. The following review summarizes the notable progress achieved within the preceding seven-year period in employing MIP-based sensing techniques for analyte determination.

Development and application of a thin-film molecularly imprinted polymer for the measurement of mycophenolic acid in human plasma

BACKGROUND

Mycophenolic acid (MPA) is used to suppress the immune response following organ transplantation; however, complex pharmacokinetic behavior and a large interpersonal variability necessitate therapeutic drug monitoring. To overcome the limitations of current sample preparation techniques, we present a novel thin-film molecularly imprinted polymer (TF-MIP) extraction device as part of a simple, sensitive, and fast method for analysis of MPA from human plasma.

METHODS

Mycophenolic acid is extracted from plasma using a tailor-made TF-MIP that is subsequently desorbed into an organic solvent system compatible with mass spectrometry. The MIP yielded higher recovery of MPA relative to a corresponding non-imprinted polymer. The method allows for the determination of MPA in 45 min including analysis time and can be scaled for high throughput to process as many as 96 samples per hour.

RESULTS

The method gave an LOD of 0.3 ng mL^-1 and was linear from 5 to 250 ng mL^-1 . Patient plasma samples (35 μL) were diluted using charcoal-stripped pooled plasma to a final extraction volume of 700 μL; when MPA in patient plasma is high, this ratio can easily be adjusted to ensure samples are within the method linear range. Intra- and inter-day variability were 13.8% and 4.3% (at 15 ng mL^-1 ) and 13.5% and 11.0% (at 85 ng mL^-1 ), respectively (n = 3); inter-device variability was 9.6% (n = 10).

CONCLUSIONS

Low inter-device variability makes these devices suitable for single use in a clinical setting, and the fast and robust method is suitable for therapeutic drug monitoring, where throughput and time-to-result are critical.

Porous agarose/chitosan/graphene oxide composite coupled with deep eutectic solvent for thin film microextraction of chlorophenols

In this project, a three-dimensional graphene oxide coated agarose/chitosan (ACGO) porous film was synthesized and utilized as sorbent in thin film microextraction (TFME) technique to extract 4-chlorophenol, 2,4-dichlorophenol, 3,5-dichlorophenol and 2,4,6-trichlorophenol as the model analytes in various real samples such as agricultural waste water, honey and tea samples. In addition, deep eutectic solvent made of tetra ethyl ammonium chloride/chlorine chloride was used as a desorption solvent. The effect of various variables, such as: extraction time, stirring rate, solvent desorption volume, desorption time, ionic strength and solution pH on the extraction efficiency of the method was studied and optimized. Under the optimized condition, the linear range of the method was obtained in the range of 0.1-500μgL^-1 for testing analytes (4-chloropheol=0.1-500μgL^-1, 2,4-dichlorophenol=0.2-500μgL^-1, 3,5-dichlorophenol=0.5-500μgL^-1 and 2,4,6-trichlorophenol=0.2-500μgL^-1). The obtained correlation coefficients (r²) were between 0.9984 and 0.9994. The limits of detection (LODs) were also calculated between 0.03 - 0.13μgL^-1. The relative standard deviations (RSDs%) were obtained in the range of 2.8 to 5.9%. The enrichment factor (EFs) values for the studied analytes were also obtained in the range of 33.4-35.8. In addition, the obtained results indicated that the prepared film can potentially be used for more applications in the field of environment, food safety, and drug analysis.

Deep eutectic solvent-based iron nanoparticles coated by N, S-doped amorphous carbon and its application in magnetic Dµ-SPE combined with DLLME for the extraction of PAHs in eyeliner

This work presents a preparation of new magnetic nanoparticles coated with amorphous carbon and their application in dispersive solid-phase extraction in simultaneous extraction of sixteen polycyclic aromatic hydrocarbons from eyeliner. The extraction procedure was hyphenated with a lower density than water dispersive liquid-liquid microextraction (DLLME) for further preconcentration of the analytes to sensitive determination of them with gas chromatography-flame ionization detection. The magnetic adsorbent was prepared sonically from iron pentacarbonyl and then the nanoparticles were coated by N, S-doped amorphous carbon and the deep eutectic solvent prepared from tetrabutyl ammonium chloride and decanoic acid. The magnetic properties of the nanoparticles were studied by vibrating sample magnetometer. Also, scanning electron microscopy was used to investigate the nanoparticles morphology. The extraction procedure was done by migration of the analytes from eyeliner into a proper aqueous solution and their adsorption onto the nanoparticles. Then, the analytes were eluted and more concentrated by the DLLME approach. After validating the method, acceptable limit of detection and broad linear range were accessed in the ranges of 0.25-0.54 and 1.8-250 ng/g, respectively. Relative standard deviation values were ≤ 7.1% for the repeated analyses in the same day (n = 6) and different days (n = 6). Extraction recovery of the method was in the range of 79-96%. The introduced method was successfully used for the analysis of the PAHs in five eyeliner samples and only two of them were identified in all samples at ng/g level.

Combination of polyurethane and polymethyl methacrylate thin films as a microextraction sorbent for rapid adsorption and sensitive determination of neonicotinoid insecticides in fruit juice and tea by ultra high performance liquid chromatography with tandem mass spectrometry

An economical and effective thin film microextraction (TFME) for simultaneous analysis of ten neonicotinoid insecticides and metabolites in fruit juice and tea, was developed based on the combination of polyurethane (PU) and polymethyl methacrylate (PMMA) films as the sorbent followed by ultra high performance liquid chromatography with tandem mass spectrometry. The PU/PMMA composite was evidenced to possess rapid adsorption and strong accumulation towards neonicotinoids compared with the films used alone. A series of parameters were optimized, and the agitation mode, film size, ionic strength, desorption solvent and sample pH were found to dominate the microextraction process rather than the extraction temperature, agitation time and sample volume. The thin films are cost effective and efficient for single use analysis, but still can be reused at least 8 times with no significant loss in performance. The ten neonicotinoids were measured with good recoveries (81.1-107.9%), high enrichment factors (up to 135), low limits of detection (0.001-0.1 µg L^-1), and wide linearity range (1-500 µg L^-1, r²>0.9981) in fruit juice (apple, lemon, and pomegranate) and tea (green tea and black tea) samples. The proposed method was successfully applied to commercial fruit and tea drinks, and no samples were tested positive on target neonicotinoids. The PU/PMMA based TFME has shown great potential as an alternative to exhaustive extraction techniques for routine screening of trace neonicotinoids in fruit juice and tea by simplifying the analytical procedure, shortening the operation time, and lowering the material expense.

Micro-gel thin film molecularly imprinted polymer coating for extraction of organophosphorus pesticides from water and beverage samples

Molecularly imprinted polymers (MIPs) have become an important class of materials for selective and efficient adsorption of target analytes. Despite versatility of MIPs for fabrication in numerous formats, these materials have been primarily reported as solid phase extraction packing materials. An effective thin film MIP prepared on stainless steel substrate is reported here for high throughput enrichment of organophosphorus pesticides (OPPs) from water and beverage samples followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. The key factors controlling performance as well as best practices for optimized fabrication of thin film MIPs are presented. A pseudo-phase diagram is introduced to evaluate and predict the effect of the ratio of porogen (solvent, 1-octanol) volume to relative crosslinker mass on the desired polymer features (i.e., porosity, surface area, capacity, and selectivity). At low porogen ratios, a macroporous polymer with insignificant selectivity is formed, whereas at high porogen ratios a micro-gel polymer with superior selectivity towards targets is obtained. The porosity and morphology determined with nitrogen adsorption and scanning electron microscopy were attributed to specific regions in the pseudo-phase diagram. Other factors influencing selectivity and stability of the polymer, such as type of the template and its ratios with monomer (methacrylic acid) and crosslinker (ethylene glycol dimethacrylate) were optimized. The prepared thin film MIPs were characterized using adsorption isotherms and adsorption kinetics, and evaluated for matrix effects (high humic acid content) and cross-reactivity in presence of other pesticides and pharmaceuticals. The optimized method provided limits of quantitation (LOQs) ranged from 0.002 to 0.02 ng mL^-1 in water and from 0.095 to 0.48 ng g^-1 in apple juice. Regarding inter-device variability (CV∼10% without normalization), excellent linearity (R² > 0.99), satisfactory accuracies (90-110%) and precisions (<15%) were obtained.

Application of curcumin as a green and new sorbent in deep eutectic solvent-based dispersive micro-solid phase extraction of several polycyclic aromatic hydrocarbons from honey samples prior to gas chromatography-mass spectrometry determination

A green, simple, and efficient dispersive micro-solid phase extraction method was developed for the extraction of polycyclic aromatic hydrocarbons from honey samples. In this method, for the first time, curcumin was used as an efficient and green sorbent to extract the analytes from the sample. After that the adsorbed analytes were eluted using a deep eutectic solvent prepared by mixing tetrabutylammonium chloride: ethylene glycol and analyzed by gas chromatography-mass spectrometry. Important experimental factors affecting adsorption and desorption steps of the method were optimized and under optimal experimental conditions, low limits of detection (0.14-0.37 ng/g) and quantification (0.49-1.3 ng/g), wide linear range (1.3-500 ng/g) with a coefficient of determination ≥0.994 were obtained. Relative standard deviation values for intra- and interday precisions were ≤7.5% for all of the analytes at a concentration of 2 ng/g for each analyte (n = 6). Extraction recovery of the method was in the range of 72-81%. Finally, 20 honey samples were analyzed and the analytes were successfully detected. The method is environment friendly because of the use of curcumin as a sorbent. Also, biodegradability of the used deep eutectic solvent components is another advantage of the method.

Thin film molecularly imprinted polymer (TF-MIP), a selective and single-use extraction device for high-throughput analysis of biological samples

Enhancing selectivity, reducing matrix effects and increasing analytical throughput have been the main objectives in the development of biological sample preparation techniques. A thin film molecularly imprinted polymer (MIP) is employed for extraction and analysis of tricyclic antidepressants (TCAs) as a model class of compounds in human plasma for the first time to reach the abovementioned goals. The thin film MIPs prepared on a metal substrate can be used directly for extraction from biological matrices with no sample manipulation steps and no pre-conditioning. This method was validated with good linearity (R² > 0.99 in 1.0-500.0 ng mL^-1 range), excellent accuracy (90% -110%) and precision (RSD % value less than 15%) in pooled human plasma samples (N = 3). The limits of quantitation (LOQ) for TCAs in plasma samples were between 1.0-5.0 ng mL^-1 which are lower than the therapeutic ranges of these drugs. Kinetic and isotherm studies showed the superior performance of MIP sorbent compared to a non-imprinted polymer (NIP) sorbent in extracting TCAs from a bovine serum albumin (BSA) solution. The optimized and validated method for pooled human plasma was utilized for monitoring the concentration of TCAs in three patient samples who had been prescribed TCAs. These selective single-use thin film extraction devices are promising for efficient and fast procedures for analyzing biological samples.

Smokeless tobacco analysis: Simultaneous extraction and purification of alkaloids, volatile N-nitrosamines, and polycyclic hydrocarbons for GC-MS/MS

Several smokeless tobacco products are available in the market and comprise complex chemical matrices. Sample preparation for analysis of the multiple classes of harmful compounds in smokeless tobacco products is highly cumbersome. In this study, a simultaneous extraction scheme was developed for three toxic analyte classes in smokeless tobacco products using a two-phase solution consisting of 5% aqueous NaOH and dichloromethane in a 1:4 ratio. The dichloromethane extract was used to analyze four alkaloids directly at levels greater than parts per million; however, passing the layer through a silica cartridge for further purification and concentration was necessary for determining 18 polycyclic aromatic hydrocarbons and four volatile N-nitrosoamines at the ppt level. The multitargets were determined by using gas chromatography with tandem mass spectrometry. The limits of detection for the 18 polycyclic aromatic hydrocarbons, four volatile N-nitrosoamines, three minor alkaloids, and nicotine were 0.2-1.2, 0.2-0.4, 0.6-1.0, and 10.2 μg/g, respectively. Four different smokeless tobacco substrates were fortified with three levels of mixed standards, and the recoveries ranged between 83 and 110%. The method was highly efficient, reduced the sample amounts, solvents, and the time required by approximately 60%. The method was used to assay 18 smokeless tobacco products, and showed potentials in assaying drugs and other plant-based substrates.

Polyvinylidene difluoride film with embedded poly(amidoamine) modified graphene oxide for extraction of chlorpyrifos and diazinon

An effective, sensitive, relatively fast, and cost-effective method was developed to determine two types of selected organophosphorus pesticides (OPPs) including diazinon and chlorpyrifos in apple, peach, and four different water samples (river, sea, well, and agriculture wastewater samples) through applying poly(amidoamine)@graphene oxide-reinforced polyvinylidene difluoride thin-film microextraction (PAMAM@GO-PVDF-TFME). The extracted analytes were desorbed via organic solvent and determined using high-performance liquid chromatography-ultraviolet detection (HPLC-UV). The strong interactions between the sorbent and selected analytes (coordination bonds, intermolecular hydrogen bonding, π-π interactions, and hydrophobic effects) made this TFME capable of high extraction performance and capacity. Several factors involved in the PAMAM@GO-PVDF-TFME experiments such as desorption volume, desorption time, sample pH, extraction time, and stirring rate were screened via Plackett-Burman design and then optimized through Box-Behnken design with the purpose of reaching the highest extraction efficiency. The above method showed a good linear range (0.5-500 μg L^-1 and 1-500 μg L^-1) with the coefficient of determination better 0.9944, low limits of determination (0.12 and 0.20 μg L^-1), good enrichment factors (99 and 98), acceptable extraction recoveries (99 and 98%), and good spiking recoveries (90-98%) under the optimized condition at three different spike levels for chlorpyrifos and diazinon, respectively. The results confirmed that the presented method would be promising for the determination of various types of these pesticides in environmental and beverage samples.

Assessment of cross-reactivity in a tailor-made molecularly imprinted polymer for phenolic compounds using four adsorption isotherm models

Cross-reactivity is an important feature of molecularly imprinted polymers (MIPs), and is central to successful use of a pseudo-template in molecular imprinting. The adsorption and cross-reactivity of a molecularly imprinted polymer (MIP) designed for recognition of phenols from water was assessed using four different isotherm models (Langmuir (LI), Freundlich (FI), Langmuir-Freundlich (L-FI), and Brunauer, Emmett, and Teller (BET)). The L-FI model succeeded in explaining the cross-reactivity behavior through the total number of binding sites, the affinity constants and heterogeneity indices of the small phenols (phenol (ph), 2-methylphenol (2-MP), 3-methylphenol (3-MP), 2-chlorophenol (2-CP), 2,4-dimethylphenol (DMP), 2,4-dichlorophenol (DCP), 4-chloro-3-methylphenol (CMP)) with evidence that the phenols compete for binding sites based on their hydrophobicity as well as π-π, π-σ and dipole-dipole intermolecular forces. The recognition of the large phenols (2,4,6-trichlorophenol (TCP), pentachlorophenol (PCP), 4-teroctylphenol (4-OP), 4-nonylphenol (4-NP), which have much higher binding affinities than the smaller phenolic compounds, was explained with the BET isotherm model that predicts that multiple layers adsorb to the adsorbed monolayer. The adsorption behavior with MIPs is also shown to be superior to corresponding non-imprinted polymers and applicability of MIPs for trace analysis is highlighted.

Comparison of Four Adsorption Isotherm Models for Characterizing Molecular Recognition of Individual Phenolic Compounds in Porous Tailor-Made Molecularly Imprinted Polymer Films

A molecularly imprinted polymer (MIP) film using catechol as the template was designed for adsorption of a range of phenols from water. Four different isotherm models (Langmuir (LI), Freundlich (FI), Langmuir-Freundlich (L-FI), and Brunauer, Emmett, and Teller (BET)) were used to study the MIP adsorption of five phenolic compounds: phenol (Ph), 2-methylphenol (2-MP), 3-methylphenol (3-MP), 2-chlorophenol (2-CP), and 4-teroctylphenol (4-OP). Each model was evaluated for its fit with the experimental data, and key parameters, including a number of binding sites and binding site energies, were compared. Though the LI, L-FI, and BET models showed good agreement for estimation of the number of binding sites and affinity for most adsorbates, no single model was suitable for all. The LI and L-FI models gave the best fitting statistics for the Ph, 2-MP, 3-MP, and 2-CP. The recognition of 4-OP, which has much higher binding affinities than the smaller phenolic compounds not attributable to hydrophobicity alone, was explained only by the BET model, which indicates the formation of multilayers. The BET model failed only with phenol. MIPs also showed higher adsorption capacities and improved homogeneity over the analogous non-imprinted polymers.