Simultaneous determination of 9-ethylphenanthrene, pyrene and 1-hydroxypyrene in an aqueous solution by synchronous fluorimetry using the double scans method and hydroxyl-propyl beta-cyclodextrin as a sensitizer
Graphical abstract
Introduction
Water quality is currently an important issue in several regions of the world. Among the several contaminants that are recognized as threats to aquatic systems, much concern has been focused on polycyclic aromatic hydrocarbons (PAHs). PAHs have been recognized as mutagenic, carcinogenic and teratogenic. In addition, PAHs have been classified as highly hazardous by the United States Environmental Protection Agency (US EPA) and the European Union (EU) due to their toxicity [1]. Therefore, there is increasing concern regarding the deleterious effects of these compounds in estuarine and coastal ecosystems because unlike other hazardous organic chemicals that have been banned or regulated in discharges, PAHs continue to be released into the environment due to several natural phenomena in addition to anthropogenic activities, such as burning of fossil fuels, oil and gas extraction, transformation and transport [2]. In the aquatic environment, although concentrations of PAHs are relatively low compared to other pollutants, its toxicity towards aquatic organisms cannot be ignored. Accumulation of PAHs in aquatic organisms can effectively alter their activities, such as development, reproduction, and behaviors. Potential threats to the ecosystem and human health can occur via bioconcentration and biomagnification. Currently, studies on the environmental behaviors and toxicity of PAHs are primarily focused on the parent PAHs, which are listed by the US EPA as priority pollutants. However, alkyl PAHs, which are important components of the entire PAHs family, have received less attention [3]. The reported concentrations of alkyl PAHs were quite comparable to those of their parent forms in air [4], water [5] and sediment samples [6]. In crude oil, the parent PAHs constitute 1–3% of the total PAH content, and alkyl PAHs typically comprise more than 90% of the total PAH content [7]. The results of previous studies indicated that unmeasured alkyl PAHs can result in a substantial underestimation of the PAH risk [8] because the parent PAHs and alkyl PAHs co-exist in real environments and may be further metabolized. To effectively and scientifically evaluate the toxicological effects of PAHs including alkyl PAHs in the aquatic environment, an analytical method for the simultaneous determination of the parent PAHs, alkyl PAHs and their metabolites is required.
Analytical methods for the determination of the parent PAHs have improved during the past decade [9], [10], [11]. However, studies on the measurement of alkyl PAHs and PAH metabolites are still rather limited, especially for alkyl PAHs. Several studies proposed methods, such as gas chromatography coupled to mass spectrometry (GC–MS) [3], [6], [12] and liquid chromatography coupled to mass spectrometry (LC–MS) [13]. In general, these methods were expensive, time-consuming, and required complicated pretreatment procedures, which are disadvantageous for routine environmental monitoring. Alkyl PAHs and PAH metabolites obtained by alkylation and metabolization processes that altered their original structures resulted in aromatic structures with delocalized π-electrons that exhibit relatively high fluorescence quantum yields. Therefore, these compounds could be determined using fluorescence spectrometry. However, chemical compounds with similar structures typically suffered from overlapping spectra, which posed a challenge for multi-component analysis. Synchronous fluorescence spectrometry is a simple modification of the conventional fluorescence technique to afford higher selectivity due to the narrowing of the spectral bands and simplification of the spectra [14]. After its introduced by Lloyd [15], this technique has been exploited for multi-components measurements [16], [17], [18]. Because PAHs have a low solubility limit, the application of the fluorescence method was hindered by only the dissolved fraction being measured. These disadvantages can be overcome by the introduction of cyclodextrins (CDs), which form inclusion complexes with poorly soluble organic compounds to improve their solubility and dissolution rate [19]. Among the CDs, beta-CD (β-CD) and hydroxyl-propyl beta-CD (HPCD) are the primary options because they have suitable cavity sizes and relatively low costs [20]. HPCD deserves special attention due to its higher aqueous solubility, lower toxicity and more hydrophobic cavity compared to the parent compound, making it a good choice for incorporation of lipophilic molecules into the CD cavity [21]. Therefore, the introduction of CDs enabled us to improve analytical measurements, eliminate or reduce solubility issues with organic compounds, augment the sensitivity and precision, and increase the selectivity of the analytical method [22]. More importantly, studies on the bioavailability and toxicity of PAHs could address the restrictions on the solubility limit by introducing CDs [23].
To the best of our knowledge, few studies have focused on the simultaneous determination of parent PAHs, alkyl PAHs and PAH metabolites. The aim of the current study was to apply synchronous fluorescence spectrometry for the simultaneous determination of parent PAHs, alkyl PAHs and PAH metabolites by selecting 9-ethylphenanthrene (9-EP), pyrene (Pyr) and 1-hydroxy-pyrene (1-OH-Pyr) as model compounds. HPCD was selected to enhance the solubility and quantum yield of the target compounds and increase the sensitivity of the method. The inclusion behaviors between HPCD and the guest molecules as well as the mechanism of the enhancing effect were studied by fluorescence spectrometry and molecular modeling using Autodock. This novel method is expected to provide an approach for the continued study of the environmental behavior and toxicity of 9-EP, Pyr and 1-OH-Pyr in environmental science.
Section snippets
Materials
The stock solutions of analytes were prepared by adding the appropriate amount of solid 9-EP (Sigma Aldrich, purity>98%), Pyr (Acros Organics, purity>98%) and 1-OH-Pyr (J&K, purity>99%), which were separately dissolved in 100 mL of dichloromethane (Xilong Chemical Plant, purity>99%) to achieve a final concentration of 1.00×10–2 mol L–1. HPCD (J&K, purity>97%) was used without any further purification. Stock solution of HPCD (1.00×10–2 mol L–1) was prepared by dissolving HPCD in water. The working
Selection of synchronous fluorescence parameters
To the best of our knowledge, the simultaneous measurement of 9-EP, Pyr and 1-OH-Pyr in water has not been previously reported. Therefore, the feasibility of measuring three components must be investigated first. The results in Fig. 1 indicates that the fluorescence emission maximum of 9-EP (3.00×10–7 mol L–1), Pyr (5.00×10–7 mol L–1) and 1-OH-Pyr (6.00×10–7 mol L–1) was located at 352 nm, 372 nm and 386 nm, respectively. The fluorescence spectra of 9-EP, Pyr and 1-OH-Pyr overlapped. Therefore, the
Conclusions
The results presented in this paper indicated that the established synchronous fluorescence method can be successfully used for the simultaneous determination of 9-EP, Pyr, and 1-OH-Pyr in aqueous solutions. Because the physicochemical parameters of 9-EP and Pyr and the m/z ratios of the three compounds were similar, good separation and detection are difficult to achieve using other methods, such as GC–MS and LC–MS. The comparison of the main characteristics of the established method with other
Acknowledgments
The authors are grateful for the financial support from the National Natural Science Foundation of China (21177102), Research Fund for the Doctoral Program of Higher Education of China (20130121130005), Open Fund of Key Laboratory of Marine Spill Oil Identification and Damage Assessment Technology (MOIDAT) (201405), and Fundamental Research Funds for the Central Universities (2013121052).
References (50)
- et al.
Acute toxic effects of pyrene on Pomatoschistus microps (Teleostei, Gobiidae): mortality, biomarkers and swimming performance
Ecol. Indic.
(2012) - et al.
Polycyclic aromatic hydrocarbons in water, mussels (Brachidontes sp., Tagelus sp.) and fish (Odontesthes sp.) from Bahía Blanca Estuary, Argentina
Estuar. Coast. Shelf Sci.
(2009) - et al.
Alkyl polycyclic aromatic hydrocarbons emissions in diesel/biodiesel exhaust
Atmos. Environ.
(2014) - et al.
Fingerprint and weathering characteristics of stranded oils after the Hebei Spirit oil spill
J. Hazard. Mater.
(2011) - et al.
Polycyclic aromatic hydrocarbons in natural waters: sources, occurrence and analysis
Trends Anal. Chem.
(1999) - et al.
Comprehensive analysis of polycyclic aromatic hydrocarbons in wastewater using stir bar sorptive extraction and gas chromatography coupled to tandem mass spectrometry
Anal. Chim. Acta
(2011) - et al.
Total alkylated polycyclic aromatic hydrocarbon characterization and quantitative comparison of selected ion monitoring versus full scan gas chromatography/mass spectrometry based on spectral deconvolution
J. Chromatogr. A
(2008) - et al.
Critical approach to synchronous spectrofluorimetry. I
Trends Anal. Chem
(2010) - et al.
Investigation on simultaneous analysis of multicomponent polycyclic aromatic hydrocarbon mixtures in water samples: a simple synchronous fluorimetric method
Talanta
(2001) - et al.
Synchronous fluorescence determination of urinary 1-hydroxypyrene, beta-naphthol and 9-hydroxyphenanthrene based on the sensitizing effect of beta-cyclodextrin
Anal. Chim. Acta
(2009)
Cyclodextrins and their uses: a review
Process Biochem.
Investigation into the causes for the changed biodegradation process of dissolved pyrene after addition of hydroxypropyl-beta-cyclodextrin (HPCD)
J. Hazard. Mater.
Explaining cyclodextrin–mycotoxin interactions using a ‘natural’ force field
Bioorgan. Med. Chem.
Interaction of artemisinin and its related compounds with hydroxypropyl-β-cyclodextrin in solution state: Experimental and molecular-modeling studies
J. Pharm. Sci.
Preparation and characterizations of solid/aqueous phases inclusion complex of 2,4-dinitroaniline with β-cyclodextrin
Carbohydr. Polym.
Crystal structure of an essential enzyme in seed starch degradation: barley limit dextrinase in complex with cyclodextrins
J. Mol. Biol.
Effects of hydroxypropyl-β-cyclodextrin and β-cyclodextrin on the distribution and biodegradation of phenanthrene in NAPL-water system
Int. Biodeter. Biodegr.
Rapid quantification of polycyclic aromatic hydrocarbons in hydroxypropyl-β-cyclodextrin (HPCD) soil extracts by synchronous fluorescence spectroscopy (SFS)
Environ. Pollut.
Cyclodextrin-enhanced fluorescence and photochemically-induced fluorescence determination of five aromatic pesticides in water
Anal. Chim. Acta
Determination of poorly fluorescent carbamate pesticides in water, bendiocarb and promecarb, using cyclodextrin nanocavities and related media
Anal. Chim. Acta
Spectrofluorimetric determination of benzoimidazolic pesticides: Effect of p-sulfonatocalix[6]arene and cyclodextrins
Anal. Chim. Acta
Synthesis and spectroscopy studies of the inclusion complex of 3-amino-5-methyl pyrazole with beta-cyclodextrin
Spectrochim. Acta. A
Enantiodifferentiation of chiral baclofen by β-cyclodextrin using capillary electrophoresis: a molecular modeling approach
J. Mol. Struct.
Spray-dried voriconazole–cyclodextrin complexes: solubility, dissolution rate and chemical stability
Carbohydr. Polym.
Determination of carbaryl and carbofuran in fruits and tap water by β-cyclodextrin enhanced fluorimetric method
Anal. Chim. Acta
Cited by (10)
Potential ability of different types of cyclodextrins to modulate the interaction between bovine serum albumin and 1-hydroxypyrene
2021, Food ChemistryCitation Excerpt :Anand and Mukherjee (Anand & Mukherjee, 2013) also found that CDs could induce the recovery of the α-helix content of BSA in the BSA-SDS (sodium dodecyl sulfate) system, and the main mechanism was that CDs could remove the SDS molecules from the BSA-SDS binding system. It is reported that CDs can form a stable inclusion complex with 1-OHPyr (Zhang, Zhu, & Zhang, 2015), and thus, the mechanism of γ-CD or HPCD to restore the helicity of BSA could be that γ-CD or HPCD can compete with BSA molecules for binding with 1-OHPyr, thereby reducing the effect of 1-OHPyr on the structure of BSA. In order to further explore the effects of CDs on the binding interaction of BSA with 1-OHPyr, the fluorescence decay curves of 1-OHPyr and BSA in different systems were determined (Fig. S6).
Green choline amino acid ionic liquids aqueous two-phase extraction coupled with synchronous fluorescence spectroscopy for analysis naphthalene and pyrene in water samples
2020, TalantaCitation Excerpt :In the constant-wavelength synchronous fluorescence spectrum, Δλ determined the shape and intensity of the spectrum and was the most important experimental parameter in the synchronous fluorescence spectrum. Δλ selection method: draw a straight line with a slope of 1 in the three-dimensional spectrum, by adjusting the intercept, the straight line passes through the two-dimensional non-overlapping parts of the two substances, different intercepts indicated different Δλ values [33]. Fig. 5A showed a three-dimensional fluorescence spectrum of Nap/Pyr after extraction.
Simultaneous determination of dissolved phenanthrene and its metabolites by derivative synchronous fluorescence spectrometry with double scans method in aqueous solution
2019, TalantaCitation Excerpt :Compared with the previous reports, the established DSFS method is simple and has a high sensitivity owing to non- pretreatment and lower LOD. A blank standard addition recovery experiment was performed to confirm the reliability of method [13]. The results are shown in Table 2.
Simultaneous determination of Magnolol and Honokiol by amino acid ionic liquid synchronous fluorescence spectrometry
2018, Spectrochimica Acta - Part A: Molecular and Biomolecular SpectroscopyCitation Excerpt :The optimum Δλ value is an essential factor for performing the synchronous fluorescence scanning technique with regards to its resolution, sensitivity and features [23]. Methods of selection Δλ value was that: (1) a straight line with scope 1 was drawn in three-dimensional fluorescence spectrum (TDFS) of analytes, and the Δλ values were represented by the intercepts of the straight line; (2) the straight line was migrated to outcrop the non-overlapping area in TDFS of analyses and the range of suitable Δλ value was represented by corresponding intercepts [16]. The TDFS of MN and HN with or without [C8MIM][Ala] was presented in Fig. 3A and B.
Effects of flooding and aging on phytoremediation of typical polycyclic aromatic hydrocarbons in mangrove sediments by Kandelia obovata seedlings
2016, Ecotoxicology and Environmental SafetyCitation Excerpt :However, the autofluorescence of root tissues was relatively stronger with a Signal/Noise (S/N) value of 8.1. Synchronous fluorescence spectrum has the ability to narrow the peak width and partly reduce the interference of background fluorescence signal (Zhang et al., 2015). In this studies, the S/N value of synchronous fluorescence spectra increased to 75.3 (the peak signal at 379.0 nm), resulting in the background fluorescence signal having almost no effect on the determination of Ant adsorbed onto root tissues.
Metal-organic framework films functionalized with nonionic conjugated polythiophenes for visual detection of PAHs
2021, Advances in Nano Research