Solid-Phase Extraction and LC with Fluorescence Detection for Analysis of PAHs in Rainwater

Preparation of Novel Solid Phase Extraction Sorbents for Polycyclic Aromatic Hydrocarbons (PAHs) in Aqueous Media

In this study, functionalized mesoporous silica was prepared and characterized as a stationary phase using various analytical and solid-state techniques, including a Fourier-transform infrared (FTIR) spectrometer, thermogravimetric analysis, and nitrogen sorption. The results confirmed the successful synthesis of the hybrid stationary phase. The potential of the prepared hybrid mesoporous silica as a solid-phase extraction (SPE) stationary phase for separating and enriching polycyclic aromatic hydrocarbons (PAHs) in both spiked water samples and real water samples was evaluated. The analysis involved extracting the PAHs from the water samples using solid-phase extraction and analyzing the extracts using a two-dimensional gas chromatograph coupled to a time-of-flight mass spectrometer (GC × GC-TOFMS). The synthesized sorbent exhibited outstanding performance in extracting PAHs from both spiked water samples and real water samples. In the spiked water samples, the recoveries of the PAHs ranged from 79.87% to 95.67%, with relative standard deviations (RSDs) ranging from 1.85% to 8.83%. The limits of detection (LOD) for the PAHs were in the range of 0.03 µg/L to 0.04 µg/L, while the limits of quantification (LOQ) ranged from 0.05 µg/L to 3.14 µg/L. Furthermore, all the calibration curves showed linearity, with correlation coefficients (r) above 0.98. Additionally, the results from real water samples indicated that the levels of individual PAH detected ranged from 0.57 to 12.31 µg/L with a total of 44.67 µg/L. These findings demonstrate the effectiveness of the hybrid mesoporous silica as a promising stationary phase for solid-phase extraction and sensitive detection of PAHs in water samples.

Solid phase extraction of 16 polycyclic aromatic hydrocarbons from environmental water samples by π-hole bonds

Through theoretical computation, it was demonstrated that perfluorobenzene can form π-hole⋅⋅⋅π bonds with polycyclic aromatic hydrocarbons (PAHs). Then, the π-hole bond was firstly introduced in solid phase extraction in which perfluorobenzene-bonded silica sorbent was synthesized and used for the solid phase extraction of sixteen PAHs in water. Compared with the traditional octadecyl silica sorbent, the perfluorobenzene-bonded silica sorbent showed higher adsorbabilities for the PAHs with 4-6 benzene rings, for which the recoveries increased by approximately 20%. Under the optimized conditions, the proposed SPE-HPLC-FLD/UV method was successfully applied for the analysis of 16 PAHs in river water and waste water samples with the limits of detection ranged from 0.002 to 0.08 μg⋅L^-1. In addition, when the perfluorobenzene-bonded silica sorbent compared with the phenyl-bonded silica sorbent, the results indicated that π-hole⋅⋅⋅π bonds between perfluorobenzene and PAHs were stronger than the π-π interactions between the PAHs and benzene in hexane solution, which highlights the remarkable potential for the application of the π-hole bond in the SPE field.

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

An organic-inorganic hybrid monolithic column doped with gold nanorods (AuNRs) was prepared and evaluated for solid phase extraction (SPE) of polycyclic aromatic hydrocarbons (PAHs). Excellent dispersibility of AuNRs in binary green porogen system consisting of 1-hexyl-3-methylimidazolium tetrafluoroborate and deep eutectic solvents (DESs) was confirmed by energy dispersive spectrometry (EDS). The particle size of the resulting AuNRs (70-90 nm) was thoroughly examined by a transmission electron microscopy (TEM). The redox system including ammonium persulfate (APS) and tetramethylethylenediamine (TEMED) was used to initiate in situ polymerization at 4 °C to prepare the hybrid monolith. The mesoporous structure of the AuNR hybrid monoliths was confirmed by scanning electron microscopy (SEM) and nitrogen adsorption. With enrichment factors (EFs) of 150- to 292-fold, the developed method was successfully applied to the determination of 10 PAHs in wastewater samples. The recoveries at a spiked level were in the range 84.9 to 99.5% with limit of detections (LODs) and relative standard deviations (RSDs) ranging from 0.02 to 0.10 μg L^-1 and 1.5 to 4.2%, respectively. The correlation coefficients (R²) for the calibration function obtained were better 0.9991 for the target compounds. Compared to the AuNR-free monolith, the extraction efficiency of the AuNR-incorporated monolith is more than two times higher. The results indicated that the doping of AuNRs is an effective approach to obtain the hybrid monolithic column with good separation ability for PAHs. Graphical abstract.

A critical review on plant biomonitors for determination of polycyclic aromatic hydrocarbons (PAHs) in air through solvent extraction techniques

Polycyclic aromatic hydrocarbons (PAHs) are hydrocarbons having two or more fused aromatic rings, released from natural (like forest fires and volcanic eruption) as well as man-made sources (like burning of fossil fuel & wood, automobile emission). They are persistent priority pollutants and continue to last for a long time in the environment causing severe damage to human health owing to their genotoxicity, mutagenicity and carcinogenicity. The study of PAHs in environment has therefore aroused a global concern. PAHs adsorption to plant cell wall is facilitated by transpiration and plant root lipids which help PAHs transfer from roots to leaves and stalks, causing more accumulation of contaminants with the increase in lipid content. Hence, these bioaccumulators can be utilized as biomonitors for indirect assessment of ambient air pollution. Efficacy of specific plants, lichens and mosses as useful biomonitors of airborne PAHs pollution has been discussed in this review along with prevalent classical and modified extraction techniques coupled with proper analytical procedures in order to gain an insight into the assessment of atmospheric PAHs concentrations. Different modern and modified solvent extraction techniques along with conventional Soxhlet method are identified for extraction of PAHs from accumulative bioindicators and analytical methods are also developed for accurate determination of PAHs. Process parameters like choice of solvent, temperature, time of extraction, pressure and matrix characteristics are usually checked. An approach of biomonitoring of PAHs using plants, lichens and mosses has been discussed here as they usually trap the atmospheric PAHs and mineralize them.

Effective solid phase extraction using centrifugation combined with a vacuum-based method for ambient gaseous PAHs

The developed SPE clean-up procedure provides much better efficiency for a group of low molecular weight PAHs than the conventional procedure. It is therefore appropriate for extraction of gaseous PAHs from ambient air samples.

Detection of Polycyclic Aromatic Hydrocarbons in Water Samples by Annular Platform-Supported Ionic Liquid-Based Headspace Liquid-Phase Microextraction

In this paper, a new method of annular platform-supported headspace liquid-phase microextraction (LPME) was designed using ionic liquid as an extraction solvent, wherein extraction stability and efficiency were improved by adding an annular platform inside the extraction bottle. The ionic liquid 1-silicyl-3-benzylimidazolehexafluorophosphate was first synthesized and proved to be an excellent extraction solvent. Coupled with liquid chromatography, the proposed method was employed to analysis of polycyclic aromatic hydrocarbons (PAHs) in water and optimized in aspects of extraction temperature, extraction solvent volume, extraction time, pH, stirring rate, and salt effect of solution. The results indicated that this method showed good linearity (R ² > 0.995) within 0.5 µg·L^-1 to 1000 µg·L^-1 for PAHs. The method was more suitable for extraction of volatile PAHs, with recoveries from 65.0% to 102% and quantification limits from 0.01 to 0.05 µg·L^-1. It has been successfully applied for detection of PAHs in seawater samples.

Determination of Polycyclic Aromatic Hydrocarbons in Wastewater by Single-Drop Microextraction Coupled to Capillary Gas Chromatography

This study describes an analytical method employing capillary gas chromatography (GC) using flame ionization detection (FID) that has been developed for the simultaneous determination of polycyclic aromatic hydrocarbons (PAHs) in wastewater, including naphthalene, 1-naphthol, 2-naphthol and anthracene. For this purpose, single-drop microextraction (SDME) was applied as a sample preparation technique. The SDME parameters such as types of extractants, volume of the microdroplet size, extraction time, stir rate and immersion depth of needle point were investigated and optimized. The method was linear in the ranges from 2.3 ×10-3to 70.0 μg·mL-1for naphthalene, 1-naphthol and anthracene, and 2.2 ×10-3to 50.0 μg·mL-1for 2-naphthol withR2≥ 0.9990. The SDME procedure allowed efficient recovery of the investigated PAHs ranging between 94 % and 104 % with a relative standard deviation (RSD) ≤4.2 for actual wastewater sampes spiked with 5, 10 and 20 μg·mL-1of PAHs, respectively. These results showed the potential of this technique for PAHs monitoring in wastewater samples. Furthermore, the investigated methods are simple, reliable, reproducible, and not expensive.

Rapid determination of polycyclic aromatic hydrocarbons in rainwater by liquid-liquid microextraction and LC with core-shell particles column and fluorescence detection

Liquid-liquid microextraction coupled to LC with fluorescence detection for the determination of Environmental Protection Agency's 16 priority pollutant polycyclic aromatic hydrocarbons in rainwater has been developed. The optimization of the extraction method has involved several parameters, including the comparison between an ultrasonic bath and a magnetic stirrer as extractant apparatus, the choice of the extractant solvent, and the optimization of the extraction time. Liquid-liquid microextraction gave good results in terms of recoveries (from 73.6 to 102.8% in rainwater) and repeatability, with a very simple procedure and low solvent consumption. The reported chromatographic method uses a Core-Shell technology column, with particle size <3 μm instead of classical 5-μm particles column. The resulting backpressure was below 300 bar, allowing the use of a conventional HPLC system rather than the more expensive ultrahigh performance LC (UHPLC). An average decrease of 59% in run time and 75% in eluent consumption has been obtained, compared to classical HPLC methods, keeping good separation, sensitivity, and repeatability. The proposed conditions were successfully applied to the determinations of polycyclic aromatic hydrocarbons in genuine rainwater samples.

Source and deposition of polycyclic aromatic hydrocarbons to Shanghai, China

Despite recent efforts to investigate the distribution and fate of polycyclic aromatic hydrocarbons (PAHs) in air, water, and soil, very little is known about their temporal change in wet deposition. As a result of increased attention to public health, a large-scale survey on the deposition flux and distribution of PAH contamination in rainwater was urgently conducted in Shanghai, China. In this study, 163 rainwater samples were collected from six sites, and 15 PAH compounds were detected by the use of a simple solid phase microextraction (SPME) technique coupled with gas chromatography-mass spectrometry. The dominant PAH species monitored were naphthalene, phenanthrene, anthracene, and fluoranthene. The concentration of total PAHs per event was between 74 and 980 ng/L, with an average value of 481 ng/L, which is at the high end of worldwide figures. The annual deposition flux of PAHs in rainwater was estimated to be 4148 kg/yr in the Shanghai area, suggesting rainfall as a major possible pathway for removing PAHs from the atmosphere. Diagnostic analysis by the ratios of An/178 and Fl/Fl+Py suggested that combustion of grass, wood, and coal was the major contributor to PAHs in the Shanghai region. Back trajectory analysis also indicated that the pollutant sources could be from the southern part of China.

Optimization of a solid-phase extraction method using centrifugation for the determination of 16 polycyclic aromatic hydrocarbons in water

A fast and reliable method for the determination of polycyclic aromatic hydrocarbons (PAHs) in water samples by solid-phase extraction (SPE) using centrifugation has been developed and optimized. A silica-based C18 cartridge was used; parameters affecting the extraction procedure such as type and volume of the elution solvent, breakthrough volume of the percolated water sample, drying of the sorbent, and evaporation of the elute have been studied. The innovation of this work was the examination of the use of a centrifugation technique in both the drying and elution steps. When combined with centrifugation, the volume of the elution solvent was reduced to 1 mL and the time for sorbent drying decreased also to 10 min under vacuum. Under optimal conditions, recoveries for the 16 U.S. EPA PAHs were between 70 and 85% and the relative standard deviation varied between 1 and 14%. Surrogate standard recoveries were similarly between 61 and 94% with a relative standard deviation between 2 and 15%. The simplicity of the described method, use of less of organic solvent, short procedure time, and good recoveries demonstrate the advantages of this environmentally friendly approach for routine analysis of numerous samples.

Development of an ionic liquid based dispersive liquid-liquid microextraction method for the analysis of polycyclic aromatic hydrocarbons in water samples

A simple, rapid and efficient method, ionic liquid based dispersive liquid-liquid microextraction (IL-DLLME), has been developed for the first time for the determination of 18 polycyclic aromatic hydrocarbons (PAHs) in water samples. The chemical affinity between the ionic liquid (1-octyl-3-methylimidazolium hexafluorophosphate) and the analytes permits the extraction of the PAHs from the sample matrix also allowing their preconcentration. Thus, this technique combines extraction and concentration of the analytes into one step and avoids using toxic chlorinated solvents. The factors affecting the extraction efficiency, such as the type and volume of ionic liquid, type and volume of disperser solvent, extraction time, dispersion stage, centrifuging time and ionic strength, were optimised. Analysis of extracts was performed by high performance liquid chromatography (HPLC) coupled with fluorescence detection (Flu). The optimised method exhibited a good precision level with relative standard deviation values between 1.2% and 5.7%. Quantification limits obtained for all of these considered compounds (between 0.1 and 7 ng L(-1)) were well below the limits recommended in the EU. The extraction yields for the different compounds obtained by IL-DLLME, ranged from 90.3% to 103.8%. Furthermore, high enrichment factors (301-346) were also achieved. The extraction efficiency of the optimised method is compared with that achieved by liquid-liquid extraction. Finally, the proposed method was successfully applied to the analysis of PAHs in real water samples (tap, bottled, fountain, well, river, rainwater, treated and raw wastewater).