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A Fiber Optic Sensor for 2,4-dichlorophenol Analysis based on Optical Composite Oxygen-sensitive Film
Abstract
A novel fiber optic sensor based on optical composite oxygen-sensitive film was developed for determination of 2,4-dichlorophenol (DCP). The optical composite oxygen-sensitive film consists of tris(2,2′-bipyridyl) dichloro ruthenium(II) hexahydrate (Ru(bpy)3Cl2) as the fluorescence indicator and iron(III) tetrasulfophthalocyanine (Fe(III)PcTs) as bionic enzyme. A lock-in amplifier was used for detecting the lifetime of the composite oxygen-sensitive film by measuring the phase delay of the sensor head. The different variables affecting the sensor performance were evaluated and optimized. Under the optimal conditions (i e, pH 6.0, 25 °C, Fe(III)PcTs concentration of 5.0·10−5 mol/L), the linear detection range, detection limit and response time of the fiber optic sensor are 3.0×10−7–9.0×10−5 mol/L, 4.8×10−8 mol/L(S/N=3), and 220 s, respectively. The sensor displays high selectivity, good repeatability and stability, which have good potentials in analyzing DCP concentration in practical water samples.
A novel fiber optic sensor based on hydrogel-immobilized enzyme complex was developed for the simultaneous measurement of dual- parameter, the leap from a single parameter detecting fiber optic sensor to a fiber optic sensor that can continuously detect two kinds of parameters was achieved. By controlling the temperature from high to low, the function of fiber sulfide sensor and fiber DCP sensor can be realized, so as to realize the continuous detection of dual-parameter. The different variables affecting the sensor performance were evaluated and optimized. Under the optimal conditions, the response curves, linear detection ranges, detection limits and response times of the dual-parameter sensor for testing sulfide and DCP were obtained, respectively. The sensor displays high selectivity, good repeatability and stability, which have good potentials in analyzing sulfide and DCP concentration of practical water samples.
The active oxygen species in the catalytic oxidation system of Fe(III)PcTs-t-BuOOH were identified, and the mechanism of the catalytic oxidation of phenolic substrates was proposed. Quinone imine molecules, the main products of catalytic oxidation reaction, can be adsorbed on the surface of CdTe QDs, resulting in their fluorescence quenching. A dual function of catalytic oxidation and fluorescence sensing was developed for the determination of dichlorophenol (DCP) based on the Fe(III)PcTs-BuOOH-CdTe QDs system. The linear detection range of DCP was 1×10−6–1.3×10−4 mol/L, and the detection limit 2.4×10−7 mol/L. This method was characterized by high selectivity, good repeatability and desirable stability, presenting promising potentials for analyzing DCP concentration in real water samples.
The dynamic characteristics of high sensitivity temperature sensor are studied by using siphon method to fill the air hole near the core of the hollow photonic crystal fiber with Cargille matching liquid, and the two ends are fused with single-mode fiber in this work. We analyzed the working principle of filled photonic crystal fiber sensor by using the standard coupling mode theory of directional coupler. The coupling process was simulated by COMSOL software. When the photonic crystal fiber filled with 10 mm liquid was scanned by tunable laser, the temperature sensitivity was 7.50 nm /°C, the average temperature response time was 0.317 s, the average release time was 3.732 s, and the temperature variation linearity was 100%. The experimental results show that the liquid filled photonic crystal fiber has the advantages of high temperature sensitivity, fast response time and good linearity.
Antifouling biocides are toxic to the marine environment impacting negatively on the aquatic ecosystems. These biocides, namely, tributyltin (TBT) and Cu(I) compounds, are used to avoid biofouling; however, their toxicity turns TBT and Cu(I) monitoring an important health issue. Current monitoring methods are expensive and time-consuming. This review provides an overview of the actual state of the art of antifouling paints' biocides, including their impact and toxicity, as well as the reported methods for TBT and Cu(I) detection over the past decade. The principles of optical fiber sensors (OFS) applications, with focus on environmental applications, and the use of organic chemosensors in this type of sensors are debated. The multiplexing ability of OFS and their application on aquatic environments are also discussed.
A new fiber optical sensor was developed for the determination of 2,4-dichlorophenol (DCP). The sensor was based on DCP oxidation by oxygen with the catalysis of iron(III) tetrasulfophthalocyanine (Fe(III)PcTs). The optical oxygen sensing film with as the fluorescence indicator was used to determine the consumption of oxygen in solution. A lock-in amplifier was used for detecting the lifetime of the oxygen sensing film by measuring the phase delay change of the sensor head. The different variables affecting the sensor performance were evaluated and optimized. Under the optimal conditions (i.e. pH 6.0, , Fe(III)PcTs concentration of 0.62 mg/mL), the linear detection range and response time of the sensor are mol/L and 250 s, respectively. The sensor displays high selectivity, good repeatability and stability, and can be used as an effective tool in analyzing DCP concentration in practical samples.
A novel system for catalytic oxidation of phenol and chlorophenol pollutant in water by tetranitro iron (II) phthalocyanine (TNFe(II)Pc) is reported for the first time. In this system, several phenolic substrates (phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol) could be easily oxidized by naturally dissolved oxygen in the presence of TNFe(II)Pc, and then rapidly combined with 4-aminoantipyrine to generate the pink dye. The catalytic oxidation process and resulting products were monitored by UV–Vis spectroscopy and high performance liquid chromatography–mass spectrometer (HPLC–MS) technique. Control experiments demonstrated that the generation of superoxide anion radical was crucial for the dye formation, and a possible mechanism involved a successive single electron transfer from phenolic substrates to O2 via the axis of TNFe(II)Pc was proposed. Potentially, this system is promising for application in chromogenic identification of phenolic pollutant.
Cobalt tetrasulfophthalocyanine (CoTSPc) was used to catalyze the oxidation of 2-chlorophenol (2-CP) and 2,4,5-trichlorophenol (TCP) using hydrogen peroxide (H2O2) as the oxidant. This CoTSPc catalyzed hydrogen peroxide oxidation of chlorophenols resulted in the formation of different types of oxidation products depending on the solvent conditions. In water/methanol conditions (where CoTSPc is mainly monomeric, and unionized forms of the phenols), phenol and hydroquinone were the main oxidation products, while in phosphate buffer solutions (pH 7 and 10 for TCP and 2-CP, respectively, where CoTSPc is mainly aggregated, and ionized forms of the phenols), benzoquinone was the main product. In contrast to CoTSPc, other MTSPc complexes studied (AlTSPc, CuTSPc and NiTSPc) exhibited no detectable catalytic effect on the oxidation of chlorophenols under the experimental conditions employed, thus proving the effect of the central metal ions on efficient catalysis of chlorophenol. Reaction pathways are proposed based on the relative time of oxidation products formation.
Photolysis of aqueous solutions of chlorophenols (4-chlorophenol, 2,4-dichlorophenol, 2,4,5-trichlorophenol and pentachlorophenol) in the presence of immobilized non-transition metal phthalocyanine photosensitizers onto Amberlite® is presented. The photosensitizers studied are: Al (AlOCPc) and Zn (ZnOCPc) octacarboxyphthalocyanines; Al (AlPcS4) and Zn (ZnPcS4) tetrasulfophthalocyanines; sulfonated phthalocyanine complexes (containing mixtures of differently substituted derivatives) of Al (AlPcSmix), Zn (ZnPcSmix), Ge (GePcSmix), Si (SiPcSmix) and Sn (SnPcSmix). Photolysis of the chlorophenols resulted mainly in the formation of chlorobenzoquinone derivatives. The complexes showed order of activity towards the transformation of pentachlorophenol as follows: ZnOCPc>SiPcSmix>SnPcSmix>ZnPcSmix>GePcSmix>ZnPcS4>AlPcSmix>AlOCPc>AlPcS4. The generation of singlet oxygen (1O2) by these immobilized MPc photosensitizers was found to play a major role in their photoactivities towards the transformation of these chlorophenols. Langmuir–Hinshelwood (L–H) kinetic model studies showed that the ZnOCPc, GePcSmix and ZnPcSmix photocatalysis occurred on the catalysts surface.
Horseradish peroxidase (HRP) is successfully in situ encapsulated into the poly(d,l-lactide-co-glycolide) (PLGA)/PEO-PPO-PEO (F108) electrospun fibrous membranes (EFMs) by emulsion electrospinning. The adsorption and degradation of pentachlorophenol (PCP) by HRP-EFMs are investigated. The experimental results show that the sorption kinetic of PCP on EFMs follows the pseudo-second-order model, and the sorption capacity is as high as 44.69mgg(-1). The sorption mechanisms of EFMs for PCP can be explained by hydrogen bonding interactions, hydrophobic interactions and π-π bonding interactions. Profiting from the strong adsorption, the removal of PCP can be dramatically enhanced by the interaction of adsorbed PCP and HRP on the surface of EFMs. For PCP degradation, the optimal pH values for free HRP and immobilized HRP are 4 and 2-4, respectively. As pH>4.7, no adsorption and degradation are observed due to the deprotonation of PCP. The removal percentages reach 83% and 47% for immobilized HRP and free HRP, respectively, at 25±1°C. The presence of humic acid can inhibit the activity of HRP and decreases the adsorption capacity of PCP because of competitive adsorption. The operational and storage stability of immobilized HRP are highly improved through emulsion electrospinning.
A flow injection cell‐based biosensor was constructed for 2,4‐dichlorophenol (DCP) analysis by using a Clark‐type oxygen electrode as a transducer. A mixed bacterial culture capable to biodegrade DCP was immobilized between a Teflon membrane and a dialysis membrane and attached to the oxygen electrode. Optimization of the flow rate, the injection volume, the carrier buffer concentration, and pH was carried out. Under optimum conditions (100 mM phosphate buffer, pH 7.50; flow rate 0.10 mL min; sample volume 100 µL), the sensor response was linear between 0.01 and 0.30 mM DCP. The detection limit was 0.02 mM DCP, and the sensor was quite stable during 5 days of operation.Supported by a grant from VR (The Swedish Research Council)‐SIDA (The Swedish International Development and Cooperation Agency) research links. The Royal Thai Government is also acknowledged for the financial support of Ms. Jongjit Jantra Msc. studies under the Higher Education Development Project: Postgraduate Education and Research Program in Chemistry (PERCH), Thailand.
A new fiber optic sensor based on the oxidation of 2,4-dichlorophenol (DCP) catalyzed by iron(II) phthalocyanine (Fe(II)Pc) was developed for the determination of DCP. The optical oxygen sensing film containing fluorescence indicator Ru(bpy)3Cl2 was used to detect the consumption of oxygen in solution. Moreover, a lock-in amplifier was used to determine the lifetime of the sensor head by detecting its phase delay change. The results reveal that the sensor has a linear detection range of 1.0×10-6 - 9.0×10-5 mol/L and a response time of 5 min. The sensor also has high selectivity, good repeatability and stability. It can be used effectively to determine DCP concentration in real samples.
A critical component in the development of highly efficient dye-sensitized solar cells is the interface between the ruthenium bipyridyl complex dye and the surface of the mesoporous titanium dioxide film. In spite of many studies aimed at examining the detailed anchoring mechanism of the dye on the titania surface, there is as yet no commonly accepted understanding. Furthermore, it is generally believed that a single monolayer of strongly attached molecules is required in order to maximize the efficiency of electron injection into the semiconductor. In this study, the amount of adsorbed dye on the mesoporous film is maximised, which in turn increases the light absorption and decreases carrier recombination, resulting in improved device performance. A process that increases the surface concentration of the dye molecules adsorbed on the TiO2 surface by up to 20% is developed. This process is based on partial desorption of the dye after the initial adsorption, followed by readsorption. This desorption/adsorption cycling process can be repeated multiple times and yields a continual increase in dye uptake, up to a saturation limit. The effect on device performance is directly related and a 23% increase in power conversion efficiency is observed. Surface enhanced Raman spectroscopy, infrared spectroscopy, and electrochemical impedance analysis were used to elucidate the fundamental mechanisms behind this observation.
The photocatalytic oxidation of phenols by oxygen has been studied in alkaline aqueous medium upon irradiation with visible light. Metal Zn(II) and Al(III) mono- and polynuclear phthalocyanine complexes, soluble in water, have been used as photocatalysts. The studied polynuclear complexes represent two-dimensional polymers, formed of condensed phthalocyanine macrocycles. The number of the phthalocyanine units in them is 3 or 4. No visible batochromic shifting is observed in the Q-band electron transition (λ=665–680 nm) of the polynuclear complexes with respect to their mononuclear analogues. This fact is an indication of a low π–π electron delocalization between the phthalocyanine units of the polynuclear complexes in the excited state. The photocatalytic activity per mole of the polynuclear complexes at pH=7 or 13 is much higher than that of the respective mononuclear phthalocyanine complexes. The high photocatalytic activity of the polymers might be explained by the proceeding of an intra-molecular triplet–triplet energy transfer between the phthalocyanine macrocycles in accordance with the mechanism of Dexter. The singlet oxygen, obtained by photon-induced energy transfer from the excited mono- and polynuclear photosensitizers, dominates the initial steps of photooxidation.The rate of photocatalytic oxidation of phenols depends on the pH of the medium and on the phthalocyanine complex aggregation degree. The products of the oxidation of phenols in alkaline medium are the same in the both cases of using mono- and polynuclear phthalocyanine complexes as catalysts. The formation of quinones is an intermediate step during the photocatalytic oxidation of phenols at pH=13 within the process of destruction of the substrate. Maleic and fumaric acids as well as carbon dioxide have been registered as final products of the photooxidation.
Using SiO2 nanoparticles as a carrier, a novel immobilized glucose oxidase (GOD) (EC1.1.3.4) was prepared via crosslinking with glutaraldehyde (GA). The optimal immobilization condition was achieved with 1% (v/v) GA, 2% (v/v) 3-aminopropiltrietoxysilane (APTS), 2.5mg GOD (in 34mg carrier) and solution pH of 6.5. The immobilized GOD showed maximal catalytic activity at pH 7.0 and 60°C, and more than 85% of initial activity at the temperature from 20°C to 80°C. After immobilization, the enzyme exhibited improved thermal, storage and operation stability. The immobilized GOD still maintained 85% of its initial activity after the incubation at 45°C for 360min, whereas free enzyme had only 23% of initial activity after the same incubation. After kept at 4°C for 30days, the immobilized and free enzyme retained 84% and 60% of initial activity, respectively. The immobilized GOD also preserved 87% of its initial activity after six consecutive operations.
In this study, photodegradation of 2,4-dichlorophenol (2,4-DCP) in aerated aqueous solution at pH 13 in the presence of hydrogen peroxide catalyzed by polydivinylbenzene-supported zinc phthalocyanine (PDVB-ZnPc) prepared from chloromethylated polydivinylbenzene and zinc phthalocyanine via a Friedel–Crafts reaction has been investigated. The reaction intermediates were identified by gas chromatography–mass spectrometry (GC–MS). The reactive oxygen species involved in the reaction were determined by electron paramagnetic resonance (EPR) technique. Based on the experimental results obtained, PDVB-ZnPc was found to be effective for removing and mineralizing the toxic 2,4-DCP in aqueous solution. The removal yield amounted to 98% after 4h of irradiation. The reaction followed pseudo-first-order kinetics, and was well fitted into the Langmuir–Hinshelwood-type equation. The optimal concentration of PDVB-ZnPc was 1.0g/l. The reaction intermediates were some biodegradable organic acids which were subsequently mineralized to CO32− and Cl− in alkaline solution. Hydroxyl radical and superoxide anion radical other than singlet oxygen were probably generated during the photodegradation of 2,4-DCP in our reaction system.
A novel fiber optic biosensor for the determination of adrenaline based on immobilized laccase catalysis and fluorescence quenching was designed and fabricated. The immobilized laccase formed by the immobilization of laccase on the CuTAPc-Fe3O4 nanoparticles composite were used to catalyze the oxidation of adrenaline and the fluorescent oxygen-sensing membrane was used to detect the consumption of oxygen. The effects of pH and temperature on laccase activity using adrenaline as the substrate were studied. The optimal pH and temperature for the activity of immobilized laccase are 5.0 and 55°C, respectively. The immobilized laccase has good thermal, storage and operation stability. The lock-in technology was used to detect the change of the life time of the oxygen-sensing membrane. By using ABTS as the electron mediator, the biosensor showed a response time of 30 sec. The biosensor has good performance in the adrenaline concentration ranges of 2.0 × 10-7 to 9.0 × 10-7 mol/l and 1.0 × 10-8 to 9.0 × 10-8 mol/l, and it also shows good stability.
A mixed-ion, amphiphilic fluorohectorite heterostructure, wherein the galleries are regularly interstratified by hydrophilic inorganic ions (Na +) and lipophilic onium ions, is shown to be an efficient electrochemical sensor for the specific determination of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and the pollutant 2,4-dicholorophenol (2,4-DCP) when incorporated at the 5 wt % level into a carbon paste electrode (CPE). The clay-modified electrode was substantially less sentive to herbicides that lack the aromatic hydroxyl groups needed for oxidation to a quinone (e.g., Illoxan and Furore). Conventional homoionic organoclays with all galleries exclusively occupied by an onium ion surfactant exhibited a lower electrochemical response to 2,4-D and 2,4-DCP oxidation when incorporated into a CPE. Similarly, low current responses were observed for a CPE modified with a homostruc-tured mixed-ion montmorillonite clay with both inorganic ions and organic onium ions co-occuping each clay gallery. The electrochemical response observed for the mixed-ion fluorohectorite heterostructure was attributed to the ability of this unique clay intercalate to achieve electrical neutrality upon oxidation of the dichlorophenoxy moiety through the facile ejection of sodium ions from the segregated inorganic galleries.
A purge-and-trap preconcentration system coupled to a GC equipped with a microwave-induced atomic emission detector was used to determine 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP) in water and soil samples. The analytes were previously leached from the solid matrices into a 5% (w/v) sodium carbonate solution using an ultrasonic probe. It was necessary to acetylate the compounds before purging them from the aqueous medium, which, at the same time, improved their chromatographic separation. After selecting the optimal experimental conditions, the performance of the system was evaluated. Each chromatographic run took 26 min, including the purge time. Detection limits for 5 ml water samples ranged from 23 to 150 ng l−1, which is lower than the limits reached using the methods proposed by the US Environmental Pollution Agency (EPA) for chlorophenols in water. For soil samples, detection limits were calculated for 7 g samples, the resulting values ranging between 80 and 540 pg g−1 for 2,4,6-TCP and 2-CP, respectively. The accuracy of the method was checked by analysing a certified reference soil, as well as fortified water and soil samples.
A rapid approach for preparing sol–gel based fiber-optic biosensor with encapsulated pH-sensitive fluorophore-acetylcholinesterase conjugates is developed for the determination of acetylcholine. The sensor consists of a pH-sensitive fluorescent indicator encapsulated with enzyme in a sol–gel network on a glass cap that can be fixed on an optical fiber and then integrated with a flow-through reactor for continuous monitoring. The sol–gel preparation procedure has been modified for maintaining a stable pH value and enzyme activity. Among the nine fluorescent indicators tested, FITC-dextran was the most suitable candidate for biosensor. The optimized ratio of TMOS:HCl:H2O and enzyme-dye:sol solution for the rapid preparation of sol–gel film were 1:3.6×10−5:2 and 3:5, respectively. The 1 mM pH 8.5 Tris–buffer had sufficient buffer capacity for acetylcholine preparation and the substrate concentration must be below 50 mM to obtain a stable pH value. The response of the developed biosensor to acetylcholine was highly reproducible (R.S.D.=3.5%, n=8). A good linearity of acetylcholine in the range from 0.5 to 20 mM was also obtained (R2=0.98). Furthermore, a 30% inhibition can be achieved within 30 min when 0.54 μM (152 ppb) paraoxon was added into the system. This indicates that the developed biosensor is suitable for the analysis of acetylcholine and organophosphorus neurotoxins.
The synthesis of simple, extensively conjugated chromophores as substitutes for 4-aminoantipyrine (4-AAP) capable of causing hyperchromic shifts when coupled with phenols is described. The 4-aminopyrazolone derivatives synthesised are subsequently applied for the spectrophotometric assay of phenolic compounds and the advantages of each of the proposed systems are highlighted. No improvement is made on the detection of para-substituted phenols as well as polychlorophenols (e.g. pentachlorophenol). An increase in the sensitivity of coupling products is obtained for certain phenolic compounds as indicated from the comparison of the individual responses. The proposed methods have analogous analytical features and in some cases show considerable improvements compared to the 4-AAP method. Beer’s law is obeyed over a wide dynamic range (up to ca. 500 μg/l) and the relative standard deviations are <3.4%. The methods are applied satisfactorily for phenol assay in real samples, however, taking into account the intrinsic differences of the methods in the responses to the various phenolic compounds.
A gas chromatograph/atomic emission detector (GC/AED) system has been evaluated for its applicability to environmental analysis. Detection limits, elemental response factors, and regression analysis data were determined for 58 semivolatile environmental contaminants. Detection limits for injected analytes ranged from 0.17 to 3.0 ng on the hydrogen 486-nm channel, from 1.0 to 5.0 ng on the nitrogen 174-nm channel, from 0.65 to 11.7 ng on the oxygen 777-nm channel, from 0.071 to 3.0 ng on the chlorine 479-nm channel, and from 0.023 to 0.038 ng on the sulfur 181-nm channel. Mean elemental response factors (ERFs) measured on these channels, relative to the carbon 496-nm channel, were hydrogen, 0.084 (mean %RSD = 6.6); nitrogen, 0.246 (mean %RSD = 19); oxygen, 0.459 (mean %RSD = 16); and chlorine, 0.417 (mean %RSD = 3.6). The higher precision obtained for hydrogen and chlorine, relative to that for nitrogen and oxygen, is attributed to the ability to scan these elemental channels in the same GC run as the carbon 496-nm channel (diode array wavelength range limitation of ∼40 nm/run). Mean ERFs of standard compounds were used to determine the molecular formulas of chlorinated hydrocarbons and chlorinated organosulfur compounds in a contaminated environmental soil sample. These formulas are in good agreement with the molecular weights and chlorine isotopic data obtained from low-resolution gas chromatography/mass spectrometry.
— Synthetic methods to obtain selectively sulfonated metallo phthalocyanines are compared. Both condensation and direct sulfonation procedures lead to mixtures of mono- to tetrasulfonated products which are resolved by reverse phase liquid chromatography in buffered aqueous-methanol. The proportion of sulfonated derivatives is examined as a function of the starting reagents in the case of the condensation method, and as a function of the temperature and reaction time in the case of the direct sulfonation procedure. The number of sulfonate groups per phthalocyanine molecule is determined by oxidative degradation of the phthalocyanine ring followed by quantitative chromatographic analysis of the sulfophthalamide and phthalamide fragments.
The metabolism of the environmental pollutant and hepatocarcinogen 2,4-dichlorophenol (2,4-DCP) was studied using microsomal fractions and whole-cells of Saccharomyces cerevisiae containing human cytochrome P450 3A4. 2,4-DCP exhibited a typical type I substrate binding spectrum with a K, of 75 microM. 2,4-DCP was metabolised into two major metabolites identified as 2-chloro-1,4-hydroxyquinone and 2-chloro-1,4-benzoquinone in microsomal fractions and whole cells of yeast expressing human cytochrome P450 3A4. A further metabolite, 1,2,4-hydroxybenzene, was also detected during biotransformation by whole cells, but was not observed in microsomal fractions. 2,4-DCP metabolism was dependent on NADPH in microsomal fractions and no activity was observed in microsomal fractions or whole cells of control transformants. Metabolites were identified by TLC followed by GC-MS.
Flow injection analysis coupled with membrane introduction mass spectrometry (FIA-MIMS) with on-line derivatization is shown to allow fast, accurate, nearly interference-free, and sensitive (low microgram/L) quantitation of phenolic compounds in water. On-line FIA derivatization of the phenolic compounds is performed by acetic anhydride acetylation in a K2CO3-buffered alkaline medium. The phenol acetates so formed efficiently permeate a silicone membrane and are directly transferred to the mass spectrometer, in which they are analyzed with selectivity and high sensitivity via selected ion monitoring. FIA-MIMS analysis was performed for aqueous solutions of phenol, 2-methylphenol, 4-chlorophenol, 4-chloro-3-methylphenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol, and detection limits in the 0.5-20 micrograms/L (ppb) range were observed for an analytical frequency of six samples/h. FIA-MIMS for phenolic compound analysis is considerably less time-consuming and labor intensive than most chromatographic methods based on liquid-liquid extraction and preconcentration procedures and is therefore applicable for on-line and in-situ monitoring of phenols in wastewaters and in the environment. FIA-MIMS employing acetic anhydride derivatization is also virtually free of interferences since it combines chemical, membrane, and enhanced MS selectivity; hence quantitation of phenolic compounds can be performed in the presence of congeners.
Significant improvements in the performance of a capillary electrophoresis (CE) microchip with an electrochemical detector are observed using a carbon nanotube (CNT)-modified working electrode. The CNT-modified electrode allows CE amperometric detection at significantly lower operating potentials and yields substantially enhanced signal-to-noise characteristics. The electrocatalytic detection is coupled to resistance to surface fouling and hence enhanced stability. Such advantages are illustrated in connection with several classes of hydrazine, phenol, purine, and amino acid compounds. Substantial minimization of surface fouling effects has been demonstrated in connection with the monitoring of phenol and tyrosine. Factors affecting the performance of the new CNT detector were assessed and optimized. CNTs from different sources are evaluated, and the effect of an anodic pretreatment is explored. The broad and significant catalytic activity exhibited by CNT-based CE detectors indicates great promise for a wide range of bioanalytical and environmental applications.
The analysis of chlorinated phenols (2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, pentachlorophenol) in river water was accomplished using off-line solid-phase extraction (SPE) and capillary electrophoresis coupled with electrochemical detection. A key to the sensitive, reproducible, and stable detection of these pollutants was the use of a boron-doped diamond microelectrode in the amperometric detection mode. An off-line SPE procedure was utilized to extract and preconcentrate the pollutants prior to separation and detection, with ENVI-Chrom P, a highly cross-linked styrene-divinylbenzene copolymer, being employed as the sorbent. Pollutant recoveries in the 95-100% range with relative standard deviations of 1-4% were achieved. The diamond microelectrode provided a low and stable background current with low peak-to-peak noise. The oxidative detection of the pollutants was accomplished at +1.05 V vs Ag/AgCl without the need for electrode pretreatment. The method was evaluated in terms of the linear dynamic range, sensitivity, limit of quantitation, response precision, and response stability. A reproducible electrode response was observed during multiple injections of the chlorinated phenol solutions with a relative standard deviation of < or =5.4%. Good electrode response stability was observed over many days of continuous use with no significant electrode deactivation or fouling. The separation efficiencies for all six pollutants were greater than 170,000 plates/m. The minimum concentration detectable for all six ranged from 0.02 to 0.2 ppb (S/N > or = 3) using a 250:1 preconcentration factor.
The 1-octyl-3-methylimidazolium hexafluorophosphate ([C8MIM][PF6]) ionic liquid was immobilized in the pores of a polypropylene hollow fiber for hollow fiber-protected liquid-phase microextraction. Analytes including 4-chlorophenol (4-CP), 3-chorophenol (3-CP), 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP) were extracted into this ionic liquid membrane, and back extracted into 10microL sodium hydroxide acceptor solution in the lumen of the hollow fiber. Then, the acceptor solution was withdrawn into the high-performance liquid chromatography (HPLC) microsyringe connected to the hollow fiber, and directly injected into the HPLC system for analysis. Some parameters that might affect the extraction efficiency were optimized, and low detection limits (0.5microgL(-1) for 4-CP, 3-CP, DCP and 1.0microgL(-1) for TCP) were obtained. Good repeatability was achieved because of the stability of the hollow fiber-supported ionic liquid membrane. The proposed procedure was applied for direct determination of the four chlorophenols in some real water samples including groundwater, river water, wastewater and tap water. All of the four chlorophenols in these water samples were under the limits of determination, and the recoveries were in the range of 70.0-95.7% at 5microgL(-1) spiked level.
A novel analytical method is presented for the determination of chlorophenols in water. This method involves pre-concentration by solid-phase microextraction (SPME) and an external desorption using a micellar medium as desorbing agent. Final analysis of the selected chlorophenols compounds was carried out by high-performance liquid chromatography (HPLC) with diode array detection (DAD). Optimum conditions for desorption, using the non-ionic surfactant polyoxyethylene 10 lauryl ether (POLE), such as surfactant concentration and time were studied. A satisfactory reproducibility for the extraction of target compounds, between 6 and 15%, was obtained, and detection limits were in the range of 1.1-5.9ngmL(-1). The developed method is evaluated and compared with the conventional one using organic solvent as a desorbing agent. The method was successfully applied to the determination of chlorophenols in water samples from different origin. This study has demonstrated that solid-phase microextraction with micellar desorption (SPME-MD) can be used as an alternative to conventional SPME method for the extraction of chlorophenols in water samples.
Endocrine disrupting (ED) chemicals are compounds that alter the normal functioning of the endocrine system, potentially causing disease or deformity in organisms and their offspring. Pesticides are used widely to kill unwanted organisms in crops, public areas, homes and gardens and medicinally to kill parasites. Many are proven or suspected to be EDs. Ancient physiological similarities between different vertebrate groups suggest that disorders observed in wildlife may indicate risks to humans. This makes accurate risk assessment and effective legislation difficult. In this paper, the hazardous properties of pesticides which are known to have ED properties are reviewed in order to assess the implications for risk assessment. As well as data on sources of exposure in the United Kingdom (UK) an assessment of the evidence on the health effects of ED pesticides is also included. In total, 127 have been identified from the literature and their effects and modes of action are listed in this paper. Using the UK as a case study, the types and quantities of pesticides used, and their methods of application are assessed, along with their potential pathways to humans. In the UK reliable data are available only for agricultural use, so non-agricultural routes of pesticide exposure have been poorly quantified. The exposure of people resident in or visiting rural areas could also have been grossly under-estimated. Material links between ED pesticide use and specific illnesses or deformities are complicated by the multifactorial nature of disease, which can be affected by factors such as diet. Despite these difficulties, a large body of evidence has accumulated linking specific conditions to ED pesticides in wildlife and humans. A more precautionary approach to the use of ED pesticides, especially for non-essential purposes is proposed.
Selective Trace Lever Analysis of Phenolic Compounds in Water by Flow Injection Analysis - film Introduction Mass Spectrometry
- R M Alberici
- R Sparrapan
- W F Jardim
- RM Alberici
Immobilization of Horseradish Peroxidase by Electrospun Fibrous films for Adsorption and Degradation of Pentachlorophenol in Water
- J F Niu
- J J Xu
- Y R Dai
- JF Niu