Preparation of gold nanorod-incorporated monolith for solid phase extraction of polycyclic aromatic hydrocarbons

Honeycomb-like triazine-based conjugated microporous polymers exhibiting simultaneous and ultrasensitive detection of fifteen polycyclic aromatic hydrocarbons using solid-phase microextraction technique

BACKGROUND

Since the severe hazard to the ecosystem and widespread distribution through biological and man-made ways of polycyclic aromatic hydrocarbons (PAHs), it is very urgent to establish the ultrasensitive analytical method to quantitatively and directly monitor PAHs in real samples. However, because of the complicated environmental matrix and their trace concentration, the pre-concentration process is a necessary step to analyze of these compounds. In this study, solid phase microextraction (SPME) technique was proposed to separate and enrich fifteen trace PAHs from environmental samples.

RESULTS

In this work, a honeycomb-like triazine-based conjugated microporous polymers (T-CMPs) were prepared by Yamamoto reaction and firstly used as SPME coating material for the ultrasensitive direct-immersion-SPME of PAHs prior to high performance liquid chromatography-fluorescence detector (HPLC-FLD). The synthesized T-CMPs was characterized using various spectroscopy and electron microscopy techniques. The unique porous network of T-CMPs might deliver abundant adsorption sites for PAHs. Orthogonal experimental design (OED) was used to investigate the influence of four experimental parameters on the enrichment ability. Under optimal situation, a wide linear range (which lasted from 0.003 to 1000 μg L-1) with the coefficients of determination (R2) varying 0.9981 to 0.9993 was obtained. The limits of detection (LODs) for the analytes varied from 0.001 to 1.650 μg L-1, and the limits of quantification (LOQs) were between 0.003 and 4.960 μg L-1. The proposed method was effectively employed to the simultaneous and ultrasensitive detection of fifteen PAHs in industrial wastewaters. The relative recoveries for PAHs analysis varied from 74.6 % to 105 % with the relative standard deviations (RSD) of 0.1 %-7.5 % in real water samples.

SIGNIFICANCE

The prepared SPME coating material exhibited a simultaneous, high extraction and adsorption capacity for fifteen PAHs due to its honeycomb-like porous structure, ultra-large specific surface area, strong π-π stacking, and hydrophobic interactions. The present research developed a novel strategy for the construction of SPME fiber coating composites and demonstrated great application potential in the field of sample pretreatment and environmental analytical chemistry.

Determination of polycyclic aromatic hydrocarbons in surface waters by high performance liquid chromatography previous to preconcentration through solid-phase extraction by using polymeric monoliths

A simple, sensitive and reproducible solid-phase extraction method using plastic cartridges containing a monolithic sorbent (m-SPE), coupled to reverse phase liquid chromatography analysis, aiming to determine fifteen polycyclic aromatic hydrocarbons in surface water samples, was developed. The sorbent was easily prepared through a thermal polymerization reaction by using a mixture of n-butyl methacrylate as non-polar monomer and ethylene glycol dimethacrylate as crosslinker contained in a typical Polypropylene syringe cartridge. The effect of different parameters (type of hydrophobic monomer, elution solvent, sample volume, sorbent amount and sorbent load capacity) on the extraction efficiency was optimized. The optimal conditions were achieved by using n-butyl methacrylate as monomer, tetrahydrofurane (THF) as solvent for sorbent cleaning, THF:acetone (1:1) as elution solvent, 25.00 mL of sample volume, 600 µL of the polymerization mixture and 60 µg L^-1 as sample loading capacity. Finally, the sorbent charge capacity, the reusability of the cartridges and the extraction efficiency of the m-SPE monolith, as compared with a typical C8 cartridge, were evaluated. Under the optimized experimental conditions, enrichment factors were between 76 and 103, relative recovery factors from 78 to 103%, accuracy values in the range of 58 to 98%, and inter-batch reproducibility values from between 2 and 10%, were obtained. The limits of detection and quantification were obtained by two different procedures: the signal to noise (S/N) ratios (3 and 10, respectively) and the IUPAC convention. The lowest LOD and LOQ values, obtained with the S/N ratios, were between 0.02 and 1.00 µg L^-1, respectively whereas with the IUPAC convention the values were between 0.07 and 5 µg L^-1. Using this procedure, several PAHs could be detected in the surface water sample taken from a river stream located in La Plata city (Buenos Aires Province, Argentina).

A hierarchical porous composite magnetic sorbent of reduced graphene oxide embedded in polyvinyl alcohol cryogel for solvent assisted-solid phase extraction of polycyclic aromatic hydrocarbons

A hierarchical porous composite magnetic sorbent was fabricated and applied to the dispersive solvent assisted-solid phase extraction of five polycyclic aromatic hydrocarbons. A sorbent was first prepared by incorporating graphene oxide, calcium carbonate and magnetite nanoparticles into a polyvinyl alcohol cryogel. The graphene oxide was converted to reduced graphene oxide using ascorbic acid and a hierarchical porous structure was produced by reacting hydrochloric acid with incorporated calcium carbonate to generate carbon dioxide bubbles which created a second network. Before extracting the target analytes, extraction solvent was introduced into the hierarchical pore network of the sorbent. The extraction was based on the partition between the analytes and introduced extraction solvent and the adsorption of analytes on reduced graphene oxide. The extraction efficiency was enhanced through π-π and hydrophobic interactions between polycyclic aromatic hydrocarbons and reduced graphene oxide and extraction solvent. The extracted polycyclic aromatic hydrocarbons were determined using HPLC coupled with fluorescence detector. The developed method was applied to extract polycyclic aromatic hydrocarbons in disposable diaper, coffee and tea samples and recoveries from 84.5 to 99.4% were achieved with relative standard deviations below 7%. The developed sorbent exhibited good reproducibility and can be reused for ten cycles. This article is protected by copyright. All rights reserved.

Improving sorption performance of a molecularly imprinted monolithic column by doping mesoporous molecular sieve SBA-15

For the first time a hybrid molecularly imprinted polymer (MIP) doped with 3-(trimethoxysilyl) propyl methacrylate (γ-MPS)-modified mesoporous molecular sieve SBA-15 for target peptide recognition has been developed. Zinc acrylate and methacrylic acid were used as binary functional monomers, and ethylene dimethacrylate was used as cross-linking agent to prepare an imprinted monolith against Val-Tyr-Ala-Leu-Lys(glutarylation) (VYALK_glu). The morphology of the polymers was characterized by scanning electron microscopy, FT-IR spectroscopy, energy dispersive spectroscopy, and ¹H NMR. The SBA-15-MPS MIP showed high recovery of 87.1% and the IF of 12.9 for the enrichment of the template peptide. When the template peptide concentration ranged from 5 to 90 μg mL^-1, the correlation coefficients (R²) for the calibration function obtained was better 0.999. The limit of detection (LOD, 0.30 μg mL^-1) and limit of quantification (LOQ, 1.0 μg mL^-1) were achieved for signal-to-noise ratios of 3:1 and 10:1, respectively. When other kinds of synthetic peptides were used as analogs, the selectivity of the SBA-15-MPS MIP was much better than the SBA-15-MPS NIP (without template peptides) with relative selectivity coefficients of 52.8-265. In contrast, little quinolones and biogenic amines are adsorbed with the SBA-15-MPS MIP. The SBA-15-MPS MIP could enrich VYALK_glu from spiked histone digestion with the average recovery of 87.8% and the relative standard deviation (RSD) of 0.99%. As a conclusion, doping of SBA-15 is an effective approach to the improvement of performance of molecularly imprinted monolith.