Optimization of solid-phase microextraction conditions for the determination of triclosan and possible related compounds in water samples

A solid-phase microextraction (SPME) method for the determination of triclosan, methyl triclosan, 2,4-dichlorophenol and 2,3,4-trichlorophenol (considered as possible triclosan metabolites) in water samples was optimised. Analytes were first concentrated on a SPME fibre, directly exposed to the sample, and then triclosan and the two chlorinated phenols on-fibre silylated using N-methyl-N-(tert.-butyldimethylsilyl)-trifluoroacetamide (MTBSTFA). Methyl triclosan remained unaffected during the derivatization step. Compounds were determined using gas chromatography in combination with mass spectrometry (GC-MS). Influence of different factors on the efficiency of extraction and derivatization steps was systematically investigated. Using a polyacrylate (PA) fibre quantification limits below 10 ng/l, and acceptable relative standard deviations, were obtained for all compounds after an extraction time of 30 min. On-fibre silylation was carried out in only 10 min. Moreover, the efficiency of the procedure was scarcely affected by the type of water sample. The method was applied to several samples of treated and raw wastewater, triclosan was found in all samples, at concentrations from 120 to 14,000 ng/l, and 2,4-dichlorophenol in most of them, at levels up to 2222 ng/l.     

Toxicity identification of gamma-ray treated phenol and chlorophenols

Ionizing radiation, such as gamma-rays and electron-beams, has been applied to modify toxicity of refractory pollutants and industrial wastewaters, however, very few studies reported the cause of toxicity changes by radiation treatment. In this work, degradation of phenol and chlorophenols (5·10⁻⁴M) by gamma-ray treatment and consequent toxicity changes were evaluated. Toxicity of 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP) was gradually decreased with increasing absorbed dose of gamma-radiation. However, in the case of phenol and monochlorophenols (2-, 3-, and 4-CPs), toxicity was dramatically increased particularly, for a dose of as low as 1 kGy. Hydroquinone, benzoquinone, catechol, chlorohydroquinone, and 4-chlorocatechol were identified to be main by-products of gamma-ray treatment. From the solid phase extraction (SPE) fractionation study, toxicity-causing by-products were found to be hydroquinone, benzoquinone, chlorohydroquinone, and/or 4-chlorocatechol.     

Detection and determination of chlorophenols and chlorophenoxyacetic acids by instrumental analysis

A quantitative method for the determination of chlorophenols and chlorophenoxyacetic acids in aqueous solutions is described. The samples investigated contained 2-chlorophenol, 2,4-dichlorophenol, 2,6-dichlorophenol, 2,4,6-trichlorophenol and their phenoxyacetic acid derivatives. The total amount of chlorophenols is determined by spectrophotometry, the ratio of individual chlorophenols by gas chromatography and the total quantity of phenoxyacetic acids by acidimetric titration. The determinations are carried out after extraction with diethyl ether, carbon tetrachloride and petroleum ether, respectively.     

Automated on-line column-switching HPLC-MS/MS method with peak focusing for measuring parabens, triclosan, and other environmental phenols in human milk

Parabens (esters of p-hydroxybenzoic acid) and triclosan are widely used as preservatives and antimicrobial agents, respectively, in personal care products, pharmaceuticals, and food processing. Because of their widespread use and potential risk to human health, assessing human exposure to these compounds in breastfed infants is of interest. We developed a sensitive method, using a unique on-line solid-phase extraction-high performance liquid chromatography-tandem mass spectrometry system with peak focusing feature, to measure in human milk the concentrations of five parabens (methyl-, ethyl-, propyl-, butyl-, and benzyl parabens), triclosan, and six other environmental phenols: bisphenol A (BPA); ortho-phenylphenol (OPP); 2,4-dichlorophenol; 2,5-dichlorophenol; 2,4,5-trichlorophenol; and 2-hydroxy-4-methoxybenzophenone (BP-3). The method, validated by use of breast milk pooled samples, shows good reproducibility (inter-day coefficient of variations ranging from 3.5% to 16.3%) and accuracy (spiked recoveries ranging from 84% to 119% at four spiking levels). The detection limits for most of the analytes are below 1 ng mL(-1) in 100 microL of milk. We tested the usefulness of the method by measuring the concentrations of these twelve compounds in four human milk samples. We detected methyl paraben, propyl paraben, triclosan, BPA, OPP, and BP-3 in some of the samples tested. The free species of these compounds appear to be the most prevalent in milk. Nevertheless, to demonstrate the utility of these measures for exposure and risk assessment purposes, additional data about sampling and storage of the milk, and on the stability of the analytes in milk, are needed.     

Development of HPLC-MS/MS method for the simultaneous determination of environmental phenols in human urine

We present a sensitive method for simultaneous determination of bisphenol A (BPA), benzophenone-3 (BP-3), 4-tert-octylphenol (t-OP), ortho-phenylphenol (OPP), four parabens (methyl, ethyl, propyl, butyl parabens) and five chlorophenols (2,4-dichlorophenol (2,4-DCP), 2,5-dichlorophenol (2,5-DCP), 2,4,5-trichlorophenol (2,4,5-triclorophenol), 2,4,6-trichlorophenol (2,4,6-TCP), and triclosan (TCS)), in human urine by high-pressure liquid chromatography (HPLC) mass spectrometry (MS). Samples were processed using enzymatic deconjugation of glucuronides followed by solid phase extraction (SPE) on a C18 cartridge and the eluate was concentrated. Analytes were separated by reversed-phase HPLC and then detected by atmospheric pressure chemical ionisation (APCI) MS and quantified by isotope dilution method. We describe details for optimisation of each step of the procedure. The sample treatment steps are straightforward and not labour-intensive and, therefore, permit a high sample throughput with excellent prospects for automation. This method shows low inter-day variation, and detection limits for most of the compounds are below 1 ng/mL in 1 mL of urine. The method accuracy was also verified by the analysis of proficiency testing urine samples.     

Radiolytic transformations of chlorinated phenols and chlorinated phenoxyacetic acids

Hydroxyl radical reactions of selected chlorinated aromatic phenols (2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol) and chlorinated phenoxyacetic acids [2,4-dichlorophenoxyacetic acid (2,4-D), 2,4-D methyl ester, 2-(2,4-dichlorophenoxy)propionic acid (2,4-DP)] were studied using the radiolysis techniques of pulse radiolysis and gamma radiolysis. Hydroxyl radical addition was the prominent reaction pathway for the chlorinated phenoxyacetic acids and also for the chlorinated phenols at pH values below the pK(a) of the compounds. A very prominent change in (*)OH reactivity was observed with the chlorinated phenoxide ions in high pH solutions. Two different reaction pathways were clearly present between the hydroxyl radical and the chlorinated phenoxide ions. One of the reaction pathways was suppressed when the concentration of chlorinated phenoxide ions was increased 10-fold. Amid a greater electron-withdrawing presence on the aromatic ring (higher chlorinated phenoxide ions), the hydroxyl radical reacted preferably by way of addition to the aromatic ring. Steady-state experiments utilizing gamma radiolysis also showed a substantial decrease in oxidation with an increase in pH of substrate.     

Certified reference samples of tetrachloromethane, tetrachloroethylene, and chlorophenol solutions

A procedure was proposed for the metrological certification of reference samples (RS) of solutions of organic compounds. The procedure consists in the determination of performance characteristics of RSs using the developed and certified procedures for the determination of mass concentrations by gas chromatography with flame ionization detection using internal standards. The selection of the internal standards and calibration procedures and the calculation of the errors of determination are considered. Certified reference samples (CRS) of tetrachloromethane, tetrachloroethylene, 2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol solutions in ethanol are developed for the quality control of drinking water     

Study of some UV filters stability in chlorinated water and identification of halogenated by-products by gas chromatography-mass spectrometry

This work studies the stability of three UV filters: 2-ethylhexyl salicylate (ES), 2-ethylhexyl 4-(dimethylamino) benzoate (EHPABA) and 2-hydroxy-4-methoxybenzophenone (BP-3), in water samples containing low concentrations of free chlorine. Moreover, 2,4-dihydroxybenzophenone (2,4-DHBP), a metabolite of BP-3, was also included in some of the performed assays. Experiments were carried out considering free chlorine and analytes concentrations at the microg mL(-1) and ng mL(-1) level, respectively. Gas chromatography with mass spectrometry was used to follow the time course of target compounds and to identify their halogenated by-products. Concentration of water samples with solid-phase extraction cartridges and derivatization (silylation) of some species were also employed to improve their detectability. Under the experimental conditions explored in this work, ES showed an acceptable stability whereas the rest of species reacted with free chlorine at significant rates following pseudo-first-order kinetics. Their half-lives ranged from 0.4 to 25 min depending on the UV filter, chlorine concentration, water pH and presence of bromide traces. For EHPABA a relatively simple degradation pathway was established. It consisted of aromatic substitution of one atom of hydrogen per chlorine or bromide. The same reaction pattern was observed for BP-3 leading, in this case, to mono- and di-halogenated by-products. In addition, several halogenated forms of 3-methoxyphenol were identified as BP-3 cleavage by-products.     

Photolytic degradation of triclosan in the presence of surfactants

The formation of 2,8-dichlorodibenzo-p-dioxin (2,8-DCDD) in the photolytic degradation of triclosan has evoked a great concern for its safety and environmental fate. The photochemical behaviour of triclosan in daily-used chemical products, in which triclosan is present in relatively high concentrations and coexists with surfactants, was, however, addressed less frequently. The present work is focused on the mechanistic aspects of triclosan photodegradation in an aqueous medium with a relatively high concentration (≥ 30 mg L⁻¹) and on the influence of pH (8.7 and 10.5) and surfactants (Triton X100, SDS, and CTMAB) on this process. The results demonstrated that photodegradation was strongly affected by the pH and the presence of surfactants. Photodegradation products, including 2,4-dichlorophenol (2,4-DCP), 5-chloro-2-(4-chlorophenoxyl)-phenol, 2,8-DCDD, dimers, trimers, and other intermediates, were identified. Based on the analysis of photoproducts, homolytic scission of ether bond, dechlorination, ring closure, and photo-polymerisation were proposed as the main routes of triclosan photodegradation.     

Sensitivity enhancement of chlorinated phenols by continuous flow liquid membrane extraction followed by capillary electrophoresis

This paper describes a new analytical system, based on the combination of continuous flow liquid membrane extraction (CFLME) enrichment and capillary electrophoresis (CE) separation, for analysis of chlorinated phenols in water samples. Five chlorinated phenols including 3-chlorophenol (3CP), 4-chlorophenol (4CP) 2,4-dichlorophenol (DCP), 2,4,6-trichlorophenol (TCP), and pentachlorophenol (PCP) were separated by CE with Tris/sodium dihydrogen phosphate solution containing methanol 1% (v/v) as the run buffer. CFLME related parameters were investigated and optimal enrichment was obtained by using 0.3 mol L(-1) Tris as acceptor and with a sample pH 5.0, a sample flow rate of 4.0 mL min(-1), and an enrichment sample volume of 150 mL. The detection limit (S/N= 3) was 6.9, 1.0, and 1.7 ng mL(-1) for DCP, PCP, and TCP, respectively. The reproducibility (RSD%, n = 6) was 5.7 for DCP, 2.5 for PCP, and 2.8% for TCP (n = 6). The proposed method was applied to the determination of chlorinated phenols in spiked water samples with relatively satisfactory recoveries.     

Narrow-band irradiation of a homologous series of chlorophenols on TiO2: charge-transfer complex formation and reactivity

The goal of this research was to investigate the formation and reactivity of charge-transfer complexes (CTCs) among a homologous series of chlorophenols on TiO2. We previously showed that 2,4,5-trichlorophenol (245TCP) forms a CTC with Degussa P25, a commercial preparation of TiO2. Here, we probe how light energy influences reactivity and product formation. Slurries of P25 containing 245TCP were irradiated at 360, 400, 430, 480, and 550 nm. At each wavelength, the amount of transformation of 245TCP correlates to the diffuse-reflectance absorbance of a 245TCP/P25 system, supporting the CTC as the cause of reaction. In addition, polymeric products are formed only under wavelengths that excite the CTC, indicating a different reaction mechanism for the CTC than for bandgap excitation of TiO2. We also found a higher quantum efficiency for CTC reactivity than for bandgap activation of the catalyst, suggesting that the photocatalytic efficiency and selectivity can be improved for certain compounds by designing catalytic materials that form CTCs with them. Furthermore, to determine how chlorine substitution patterns affected adsorption and sub-bandgap reactivity, P25 slurries containing phenol, 4-chlorophenol, 2,4-dichlorophenol, or 2,4,6-trichlorophenol were probed following dark contact or irradiation at 360, 430, or 550 nm. With respect to the extent of adsorption, complexation, reaction, and polymerization on P25, the behavior of 245TCP far exceeded that of the other chlorophenols. Among these chlorophenols, only 2,4-dichlorophenol produced a polymeric product. 245TCP is unique among this family of chlorophenols, which we attribute to a chlorine arrangement that leads to a favorable orbital overlap with TiO2 and sterically permits coupling reactions. Our results demonstrate the critical role that charge-transfer complexation can play in determining the rates and products of photocatalytic reactions.     

Liquid chromatography/time-of-flight mass spectrometric analyses for the elucidation of the photodegradation products of triclosan in wastewater samples

Liquid chromatography coupled with time-of-flight mass spectrometry (LC/TOFMS) was applied for the identification of four new photodegradation products of triclosan, a major antimicrobial agent used in personal care products. Wastewater samples, spiked at 7 microg/mL with triclosan, were irradiated with natural sunlight in order to generate the photodegradation products. Aliquots of the spiked water samples were taken at different times of irradiation and compounds were isolated from the water samples by solid-phase extraction. Separation and detection of the compounds and degradation products were accomplished by LC/TOFMS, which provided highly selective information about elemental compositions. Accurate mass measurements for the four degradation products permitted postulation of proposed empirical formulae in this study. Replacement of chlorine atoms by hydroxyl groups and chlorine losses are the major degradation pathways proposed. The degradation products were formed also under environmental conditions in wastewater matrices, thus suggesting their presence in real wastewater treatment processes.     

Comparison of two different derivatization procedures for the determination of urinary chlorophenol excretions

A GC/MS method with enhanced sensitivity and specificity suitable for the determination of various chlorophenols in the urine of persons occupationally and environmentally exposed to diverse chlorinated aromatic hydrocarbons has been elaborated and compared with the method customarily used. After acid hydrolysis and steam distillation, followed by several clean-up steps, the chlorophenols have been derivatized with N-heptafluorobutyrylimidazole (HFBI), yielding ester derivatives. This procedure facilitates the detection of 3-and 4-monochlorophenol, 2,4- and 2,5-dichlorophenol, 2,4,5-and 2,4,6-trichlorophenol as well as 2,3,4,6-tetrachlorophenol down to 0.1–1 g/l, depending on the number of chlorine atoms. A comparison to the commonly used derivatization procedure with diazomethane revealed, except for 2,4,5-trichlorophenol, satisfactory conformity of both techniques. Due to an improvement of the detection limit by a factor of five for the monochlorophenols, for the first time the quantification of 3-monochlorophenol and the identification of 2-monochlorophenol as constituents of human urine have been possible as HFBI-derivatives. The excretion of mono-, di-, tri- and tetrachlorophenols in the urine of the general population could be confirmed.     

Formation of halogenated by-products of parabens in chlorinated water

Chemical transformations of four alkyl esters of p-hydroxybenzoic acid, parabens, in chlorinated water samples are investigated. Quantification of the parent species and identification of their reaction by-products were performed using gas chromatography in combination with mass spectrometry. Experiments were accomplished considering free chlorine and paraben concentrations at the mg L⁻¹ and μg L⁻¹ level, respectively. Concentration of water samples, using solid-phase extraction, and silylation of the target species were carried out in order to improve the detectability of parent species and their possible transformation products, achieving quantification limits at the low ng L⁻¹ level. Under employed experimental conditions, the decrease in the concentrations of parabens followed pseudo-first-order kinetics. Half-lives values obtained for model ultrapure water solutions were in good agreement with those observed in tap water samples. For the first type of sample, only two by-products were detected for each paraben. They corresponded to chlorination of the aromatic ring in one or two carbons situated in ortho-positions to the hydroxyl group. Both species were also generated after the addition of parabens to chlorinated tap water. Moreover, three new transformation products were noticed for each parent compound. They were identified as bromo- and bromochloro-parabens, formed due to the existence of traces of bromide in tap water sources. Experiments carried out by mixing paraben-containing personal care products with tap water, containing free chlorine, confirmed the formation of all above described halogenated by-products. In addition, the presence of the di-chlorinated forms of methyl and propyl paraben has been detected for first time in raw sewage water samples.     

Identification and determination of phenols and chloro-phenols in very dilute aqueous solutions by gas-liquid chromatography,paper chromatography and spectrophotometry

After concentration of the organic substances from water samples of 700 to 20,000 l by adsorption on active carbon and desorption with chloroform in a large Soxhlet apparatus, tlie organic compounds were separated by extraction into 5 different groups: acids, phenols, bases, neutral and amphoteric substances. The phenol group was investigated by gas and paper chromatography, ultraviolet difference spectrophotometry and infrared spectroscopy. Phenol, 2,4,6-trichlorophcnol, 2- and 3-cresol, 2,4-xylenol and 2,4-dichlorophenol were identified in samples of raw and treated water. Quantitative measurements proved to be possible with gas chromatography. The conditions for quantitative desorption and separation were studied.     

Degradation of Triclosan under Aerobic, Anoxic, and Anaerobic Conditions

Triclosan (2, 4, 4??-trichloro-2??-hydroxyl diphenyl ether) is a broad-spectrum antimicrobial agent present in a number of house hold consumables. Aerobic and anaerobic enrichment cultures tolerating triclosan were developed and 77 bacterial strains tolerating triclosan at different levels were isolated from different inoculum sources. Biodegradation of triclosan under aerobic, anoxic (denitrifying and sulphate reducing conditions), and anaerobic conditions was studied in batch cultures with isolated pure strains and enrichment consortium developed. Under aerobic conditions, the isolated strains tolerated triclosan up to 1?g/L and degraded the compound in inorganic-mineral-broth and agar media. At 10?mg/L level triclosan, 95?±?1.2% was degraded in 5?days, producing phenol, catechol and 2, 4-dichlorophenol as the degradation products. The strains were able to metabolize triclosan and its degradation products in the presence of monooxygenase inhibitor 1-pentyne. Under anoxic/anaerobic conditions highest degradation (87%) was observed in methanogenic system with acetate as co-substrate and phenol, catechol, and 2, 4-dichlorophenol were among the products. Three of the isolated strains tolerating 1?g/L triclosan were identified as Pseudomonas sp. (BDC 1, 2, and 3).     

Photodegradation of chlorophenolic compounds using zinc oxide as photocatalyst: experimental and theoretical studies

Zinc oxide nanoparticles were synthesized via the sol?Cgel method. The structures of the obtained nanoparticles were investigated by X-ray diffraction. The photocatalytic degradation of chlorophenolic compounds, namely 2-chlorophenol (CP), 2,4-dichlorophenol (DCP) and 2,4,6-trichlorophenol (TCP), was carried out using ZnO nanoparticles under solar intensity of 20?C26?W?m^?2. The photocatalytic degradation efficiency of TCP?<?DCP?<?CP was found. The adsorption energies of the chlorophenolic compounds with ZnO catalyst were calculated from quantum chemical molecular dynamic model and found to increase in the order of TCP?<?DCP?<?CP.     

Stir bar sorptive extraction with in situ derivatization and thermal desorption-gas chromatography-mass spectrometry for determination of chlorophenols in water and body fluid samples

A new method, stir bar sorptive extraction (SBSE) with in situ derivatization and thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS), which is used for the determination of trace amounts of chlorophenols, such as 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TrCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP) and pentachlorophenol (PCP), in tap water, river water and human urine samples, is described. The derivatization conditions with acetic acid anhydride and the SBSE conditions such as extraction time are investigated. Then, the stir bar is subjected to TD followed by GC-MS. The detection limits of the chlorophenols in tap water, river water and human urine samples are 1-2, 1-2, and 10-20 pg ml⁻¹ (ppt), respectively. The calibration curves for the chlorophenols are linear and have correlation coefficients higher than 0.99. The average recoveries of the chlorophenols in all the samples are higher than 95% (R.S.D. < 10%) with correction using added surrogate standards, 2,4-dichlorophenol-d₅, 2,4,6-trichlorophenol-¹³C₆, 2,3,4,6-tetrachlorophenol-¹³C₆ and pentachlorophenol-¹³C₆. This simple, accurate, sensitive and selective analytical method may be applicable to the determination of trace amounts of chlorophenols in liquid samples.     

在饮水中典型溶解性有机氮酪氨酸氯化生成氯仿的机理分析

饮用水氯化消毒可以有效杀灭细菌, 但同时会产生危害人体健康的消毒副产物(DBP). DBP生成机理研究是有效控制DBP的前提. 溶解性有机氮(DON)是DBP的重要前体物, 选取典型DON-丙氨酸(Ala)、苯丙氨酸(Phe)和酪氨酸(Tyr)作为氯仿(CF)等DBP的前体物, 研究三种氨基酸(AA)的耗氯量和CF产率; 同时考察了Tyr氯化中间产物2,4,6-TCP的氯化特性和CF产率; 采用GC/MS扫描和前线轨道理论验证, 探讨了CF的主要生成路径. 研究发现, 在同等氯化反应条件下, 由于侧链基团的不同, Tyr的耗氯量以及CF产率都明显高于Ala和Phe, 从而说明Tyr确实是一种重要的CF前体物质. CF的主要生成路径为Tyr→ 4-MCP → 2,4-DCP → 2,4,6-TCP → CF. 氯胺消毒工艺可有效控制CF的生成, 并能减少2,4,6-TCP的产生, 但不能确保饮用水的生物安全性. 氯化消毒之前将Tyr等重要前体物去除可能是控制CF等DBP更加有效的措施.     

Determination of phenol in landfill leachate by using microchip capillary electrophoresis with end-channel amperometric detection

Phenol, 2,4-dichlorophenol (2,4-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP) were baseline separated by using a homemade microchip CE with an end-channel amperometric detector where a 50 microm Pt microdisk working electrode (WE) and a Pt cathode were integrated onto the microchip itself. Separation parameters such as injection time and voltage, pH of the buffer, online pretreatment condition for WE, reproducibility, and detection potential were investigated. Under the selected separation conditions, the linear ranges for phenol, 2,4-DCP, and 2,4,6-TCP were 2-200, 4-400, and 4-400 microM, respectively. The LODs were 0.4, 0.5, and 0.7 microM for phenol, 2,4-DCP, and 2,4,6-TCP, respectively (S/N = 3). The standard addition method was successfully applied to the analysis of landfill leachate samples and the concentration of phenol in the landfill leachate samples was measured to be 0.32 and 0.21 mM, respectively. The recoveries were in the range of 85-103% and corresponding RSDs were less than 5.5%.