Simultaneous determination of "earthy-musty" odorous haloanisoles and their corresponding halophenols in water samples using solid-phase microextraction coupled to gas chromatography with electron-capture detection

Pooled Nanoparticle Screening Using a Chemical Barcoding Approach

We report the development of a small molecule-based barcoding platform for pooled screening of nanoparticle delivery. Using aryl halide-based tags (halocodes), we achieve high-sensitivity detection via gas chromatography coupled with mass spectrometry or electron capture. This enables barcoding and tracking of nanoparticles with minimal halocode concentrations and without altering their physicochemical properties. To demonstrate the utility of our platform for pooled screening, we synthesized a halocoded library of polylactide-co-glycolide (PLGA) nanoparticles and quantified uptake in ovarian cancer cells in a pooled manner. Our findings correlate with conventional fluorescence-based assays. Additionally, we demonstrate the potential of halocodes for spatial mapping of nanoparticles using mass spectrometry imaging (MSI). Halocoding presents an accessible and modular nanoparticle screening platform capable of quantifying delivery of pooled nanocarrier libraries in a range of biological settings.

Degradation of odorous sulfide compounds by different oxidation processes in drinking water: Performance, reaction kinetics and mechanism

Swampy/septic odor caused by various sulfides is one of the most frequently encountered odor problems in drinking water. However, even though it is much more offensive, few studies have specifically focused on swampy/septic odor compared to the extensively studied musty/earthy problems. In this work, four sulfide odorants, diamyl sulfide (DAS), dipropyl sulfide (DPS), dimethyl disulfide (DMDS) and diethyl disulfide (DEDS), were selected to evaluate the treatment performance of different oxidation processes in drinking water. The results demonstrated that DMDS, DEDS, DPS and DAS could be oxidized effectively by KMnO_4, NaClO and ClO₂. The oxidation processes could be well described by the second-order kinetic model, in which k values of selected sulfides followed the order DMDS≈DEDS ≪ DPS≈DAS. As for the three oxidants, the order of reactivity was KMnO₄ ≪ ClO₂ < NaClO, which was also verified in raw water. The results of oxidation treatability, reaction kinetics and mechanisms confirmed that the characteristics of the central sulfur atom rather than the side chain is the decisive factor in controlling the oxidation rate and transformation pathway of sulfides. The transformation products and pathways were significantly different for the three oxidants. Sulfones (DPSO, DASO) were always formed by cycloaddition reactions during KMnO₄ oxidation, yet recombination reactions proceeded during ClO₂ oxidation and formed more products, such as MADS, DADS and EADS. Density functional theory (DFT) calculations confirmed that the differences in transformation pathways were caused by the variations in the activity of the oxidants and sulfides. Finally, NaClO was certified as the most effective oxidant for controlling sulfide odorants in drinking water treatment.

Formation of odorant haloanisoles and variation of microorganisms during microbial O-methylation in annular reactors equipped with different coupon materials

Taste and odor (T & O) issues in drinking water have become serious problems which cannot be ignored by customers. Several studies have confirmed that microbes in water can biotransform halophenols (HPs) to haloanisoles (HAs) with earthy and musty flavors via microbial O-methylation. In this paper, the formation of 2-chloroanisole (2-CA), 2,4-dichloroanisole (2,4-DCA), 2,4,6-trichloroanisole (2,4,6-TCA), 2,3,6-trichloroanisole (2,3,6-TCA) and 2,4,6-tribromoanisole (2,4,6-TBA), and the microbial variation during the microbial O-methylation were investigated in annular reactors (ARs) with three coupon materials. For precursors, 42.5% of 2-CP and 68.9% of 2,4-DCP decayed during the reaction. Among the five HAs, the formation rate constant followed an order of 2,4,6-TCA > 2-CA > 2,4,6-TBA > 2,4-DCA ~ 2,3,6-TCA, while [HA]_max followed a totally opposite one. The simulated flow velocity had no significant effect (p > 0.05) on HA formation. Ductile iron (DI) AR could produce more HAs than stainless steel (SS) and polyvinyl chloride (PVC) ARs. The final HA molar concentration followed an order of 2,3,6-TCA > 2,4-DCA > 2,4,6-TBA ~ 2,4,6-TCA > 2-CA, which might be explained by multiple factors including HP's dissociation degree, halogen atom's steric hindrance and specificity of HP O-methyltransferases. During the reaction, the microbial biomass dramatically increased 6.8-9.0 times in bulk water but dropped significantly on coupon biofilms. The effect of HPs significantly changed the bacterial communities on coupon in terms of composition and diversity, and declined the relative abundance of HA-producing bacteria, while fungi and their HA-producing genus showed better resistance ability towards HPs. By using Pearson correlation analysis, a significant correlation (p = 0.0003) was found between [HA]_max and initial coupon biofilm biomass. Finally, a linear relationship was established between initial total biomass and HA formation potential.

Source water odor in one reservoir in hot and humid areas of southern China: occurrence, diagnosis and possible mitigation measures

BACKGROUND

Identifying typical odor-causing compounds is essential for odor problem control in drinking water. In this study, aiming at a major water source reservoir in hot and humid areas in southern China, which encountered seasonable odor problems in recent years, an integrated approach including comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC × GC-TOFMS), flavor profile analysis (FPA) and quantitative real-time polymerase chain reaction (qPCR) was adopted to investigate the odor occurrence.

RESULTS

The results indicated that earthy-musty odor is blamed to the seasonable odor problems, and it is consistent with the complaints results from consumers. Fifty-four typical odor compounds were investigated in the reservoir and twelve were detected, of which, 2-methylisoborneol (2-MIB) was significantly increased during the odor event. Pseudanabaena sp. is the dominant species in the reservoir, which can be further represented by the number of mic gene with qPCR method (R ² = 0.746, P < 0.001). Oxygen consumption (COD_Mn) and dissolved organic carbon (DOC) have great influence on growth of Pseudanabaena sp., and the release of 2-MIB from the Pseudanabaena sp. cells is affected by temperature and light.

CONCLUSION

Our findings demonstrated that 2-MIB is the odor-caused substance in the reservoir and Pseudanabaena sp. is the main 2-MIB producer, which was confirmed as a benthic filamentous algae. Due to COD_Mn and DOC have great influence on Pseudanabaena sp. growth, further measures to reduce the CODMn and DOC input should be performed. We also demonstrated that the 2-MIB release is affected by temperature and light. The risk of sudden increase of 2-MIB will be reduced by raising the depth of water in the reservoir. Our study will improve the understanding of T&O problems in this city, as well as in other hot and humid area.

Pilot investigation on formation of 2,4,6-trichloroanisole via microbial O-methylation of 2,4,6-trichlorophenol in drinking water distribution system: An insight into microbial mechanism

Taste & odor (T&O) problems in drinking water are always complained by customers. Recent studies have indicated biofilms in drinking water distribution system (DWDS) are always ignored as potential sources of T&O compounds. In this paper, the formation of 2,4,6-trichloroanisole (2,4,6-TCA), one of the dominant T&O compounds, was investigated in a pilot-scale DWDS. The addition of precursor 2,4,6-trichlorophenol (2,4,6-TCP) of 0.2 mg/L induced the formation of 2,4,6-TCA with a maximum yield of ∼400 ng/L, and the formation kinetics can be described by a pseudo-first-order kinetic model. Effects of water distribution factors such as pipe material, temperature, flow velocity, and residual chlorine on the formation of 2,4,6-TCA were evaluated, and the pipe material was found to have the most remarkable effect. Ductile iron and stainless steel pipes produced much more 2,4,6-TCA than polyethylene (PE) pipe. The biofilm microbial communities on the three types of pipe walls were then comprehensively analyzed by heterotrophic plate count and 16S rRNA/ITS1 genes high throughput sequencing. The links between the 2,4,6-TCA formation potential and the microbial activity in genus and enzymatic levels in DWDS have been revealed for the first time. According to the characteristics of microbial assemblages of producing 2,4,6-TCA, quorum-sensing (QS) bacterial signaling system and extracellular DNA (eDNA) may be two promising targets for biofilm treatment and 2,4,6-TCA control in DWDS.

The occurrence of haloanisoles as an emerging odorant in municipal tap water of typical cities in China

In this study, occurrence of the haloanisoles odorous compounds in tap water of Chinese cities, were investigated by solid-phase microextraction (SPME)-GC/MS analysis. This study revealed the occurrence of four kinds of haloanisoles in 22 cities of China in both summer and winter. Except 2,4,6-tribromoanisole (2,4,6-TBA), all studied haloanisoles showed higher frequency of detection. 2,3,6-Trichloroanisole (2,3,6-TCA) and 2,3,4-trichloroanisole (2,3,4-TCA) showed higher occurrence concentration; however, the relative odor values of them was lower. These values of 2,4,6-TBA and 2,4,6-trichloroanisole (2,4,6-TCA) in all samples were greater than zero in both summer and winter, indicating the odor from haloanisoles could be felt by human noise. This study further showed that Beijing exhibited most serious occurrence of haloanisoles that were depended on the season and drinking water distribution system (country and city). From this study, it was confirmed that haloanisoles was important taste and odor compounds in tap water of China. Based on the survey of occurrence of halophenol and residual chlorine, the possible source for the formation of haloanisoles in tap water was discussed. Furthermore, several suggestions on control the haloanisoles odor in drinking water treatment plant and water distribution system were provided.

Determination of Chlorophenols in Water Samples Using Solid-Phase Extraction Enrichment Procedure and Gas Chromatography Analysis

Solid-phase extraction (SPE) procedure followed by derivatization and gas chromatography electron capture detection was evaluated for the determination of trace amounts of chlorophenols (CPs) in waters samples. Different parameters affecting extraction efficiency such as, volume of elution solvent, volume and pH of water sample, quantity of sorbent phase were studied and optimized. SPE was carried out on polystyrene-divinylbenzene (Bond Elut ENV) and high recoveries were obtained using 1000 mg of this cartridge for the treatment of 500 mL of acidified water sample. The described method was then tested on spiked tap, mineral, ground and surface water samples. The overall procedure provided limits of detection lower than 20 ng L(-1), recoveries of 70%-106% and an enrichment factor of 500 for the examined CPs in 500 mL water samples. Among the studied compounds, pentachlorophenol was detected in tap water at a concentration level of 0.06 µg L(-1).

Parameters optimization using experimental design for headspace solid phase micro-extraction analysis of short-chain chlorinated paraffins in waters under the European water framework directive

The water framework directives (WFD 2000/60/EC and 2013/39/EU) force European countries to monitor the quality of their aquatic environment. Among the priority hazardous substances targeted by the WFD, short chain chlorinated paraffins C10-C13 (SCCPs), still represent an analytical challenge, because few laboratories are nowadays able to analyze them. Moreover, an annual average quality standards as low as 0.4μgL(-1) was set for SCCPs in surface water. Therefore, to test for compliance, the implementation of sensitive and reliable analysis method of SCCPs in water are required. The aim of this work was to address this issue by evaluating automated solid phase micro-extraction (SPME) combined on line with gas chromatography-electron capture negative ionization mass spectrometry (GC/ECNI-MS). Fiber polymer, extraction mode, ionic strength, extraction temperature and time were the most significant thermodynamic and kinetic parameters studied. To determine the suitable factors working ranges, the study of the extraction conditions was first carried out by using a classical one factor-at-a-time approach. Then a mixed level factorial 3×2(3) design was performed, in order to give rise to the most influent parameters and to estimate potential interactions effects between them. The most influent factors, i.e. extraction temperature and duration, were optimized by using a second experimental design, in order to maximize the chromatographic response. At the close of the study, a method involving headspace SPME (HS-SPME) coupled to GC/ECNI-MS is proposed. The optimum extraction conditions were sample temperature 90°C, extraction time 80min, with the PDMS 100μm fiber and desorption at 250°C during 2min. Linear response from 0.2ngmL(-1) to 10ngmL(-1) with r(2)=0.99 and limits of detection and quantification, respectively of 4pgmL(-1) and 120pgmL(-1) in MilliQ water, were achieved. The method proved to be applicable in different types of waters and show key advantages, such as simplicity, automation and sensitivity, required for the monitoring programs linked to the WFD.

Seasonal and spatial variations of source and drinking water quality in small municipal systems of two Canadian regions

A one-year sampling program covering twenty-five small municipal systems was carried out in two Canadian regions to improve our understanding of the variability of water quality in small systems from water source to the end of the distribution system (DS). The database obtained was used to develop a global portrait of physical, chemical and microbiological water quality parameters. More precisely, the temporal and the spatial variability of these parameters were investigated. We observed that the levels of natural organic matter (NOM) were variable during different seasons, with maxima in the fall for both provinces. In the regions under study, the highest trihalomethane (THM) and haloacetic acid (HAA) levels were achieved in warmer seasons (summer, fall), as observed in previous studies involving large systems. Observed THM and HAA levels were three times higher in systems in the province of Newfoundland & Labrador than in the province of Quebec. Taste and odor indicators were detected during the summer and fall, and higher heterotrophic plate count (HPC) levels were associated with lower free chlorine levels. To determine spatial variations, stepwise statistical analysis was used to identify parameters and locations in the DS that act as indicators of drinking water quality. As observed for medium and large systems, free chlorine consumption, THM and HAA levels were dependent on their location in the DS. We also observed that the degradation of HAAs is more important in small systems than in medium or large DS reported in the literature, and this degradation can occur from the beginning of the DS. The results of this research may contribute to providing precious information on drinking water quality to small system operators and pave the way for several opportunities to improve water quality management.

Development of polypropylene coated hollow fiber membranes as passive sampler for field equilibrium sampling of odorous compounds in environmental waters

A new passive sampling device was developed for field equilibrium sampling of geosmin (GSM) and 2-methylisoborneol (MIB) in surface water. The sampling device was prepared by coating a 50 cm length polypropylene hollow fiber tubing (50 μm wall thickness, 280 μm inner diameter) with polypropylene glycol 4000. The sampler was brought into equilibrium with the sample in the field, and then transferred and immersed into 100 μL of methanol held in a little desorption device for room temperature desorption and preservation of the sampled analytes. After being transported to the laboratory, the analytes were determined by headspace solid-phase microextraction-GC-MS. The large surface area-to-volume ratio of the developed sampler facilitated the reaching of sampling equilibrium in 1 h, while the equilibrium sampling minimized the effects of environmentally relevant sampling conditions. Variation of sample pH (4.0-9.0) and salinity (0-100 mM NaCl) had no significant effects on the distribution coefficients of analytes to the sampler. The desorption device, constructed with a 200 μL glass insert, and a 2 mL brown glass vial with PTFE sealed screw cap, has no loss of analytes during the storage of the sampler. The proposed procedure had detection limits of 4 and 9 ng L-1 for GSM and MIB, respectively. This developed sampler was successfully applied to field sampling in Taihu Lake (China), with MIB and GSM detected in the range of 0.11-0.61 μg L-1 during a medium out-break of blue-green algae bloom.

Les goûts et les odeurs dans l’eau potable : revue des composés responsables et des techniques de mesure

L’évaluation de la qualité de l’eau potable d’un réseau de distribution est souvent faite en tenant compte des normes physico-chimiques et microbiologiques édictées par les réglementations nationales. L’approche par barrières multiples permet aussi d’assurer aux consommateurs une eau avec une sécurité sanitaire optimale. Cependant, malgré les sommes investies par les municipalités pour se conformer à ces normes, les consommateurs renoncent fréquemment à consommer l’eau du robinet.

Ce refus peut être attribué, entre autres, à la qualité organoleptique (goût, odeur) de l’eau distribuée par les réseaux d’aqueduc. Toutefois, cet aspect est peu pris en compte par les législations actuelles et, conséquemment, est peu considéré par les gestionnaires des réseaux d’eau potable. De plus, les méthodes utilisées pour évaluer les molécules responsables des goûts et des odeurs de l’eau distribuée exigent de l’équipement spécialisé et coûteux. Cet article présente une revue de la problématique des composés responsables des goûts et des odeurs. Les aspects concernant les origines de ces composés, les méthodes quantitatives et qualitatives développées jusqu’à présent pour les analyser et la faisabilité d’application desdites méthodes, selon leurs avantages et leurs limites, seront abordés.

Chronic exposure to environmental levels of tribromophenol impairs zebrafish reproduction

Tribromophenol (2,4,6-TBP) is ubiquitously found in aquatic environments and biota. In this study, we exposed zebrafish embryos (F(0); 2"" days post-fertilization, dpf) to environmental concentration (0.3 microg/L) and a higher concentration (3.0 microg/L) of TBP and assessed the impact of chronic exposure (120 dpf) on reproduction. TBP exposure did not cause a significant increase in the malformation and reduction in the survival in the F(0)-generation fish. After TBP exposure, the plasma testosterone and estradiol levels significantly increased in males and decreased in females. The transcription of steroidogenic genes (3beta-HSD, 17beta-HSD, CYP17, CYP19A, CYP19B) was significantly upregulated in the brain and testes in males and downregulated in the brain and ovary in females. TBP exposure significantly downregulated and upregulated the expression of VTG in the liver of female and male fish, respectively. Meanwhile, TBP exposure altered the sex ratio toward a male-dominant state. The F(1)-generation larvae exhibited increased malformation, reduced survival, and retarded growth, suggesting that TBP in the aquatic environment has significant adverse effects on fish population.

Evaluation of solid-phase microextraction conditions for the determination of chlorophenols in honey samples using gas chromatography

A rapid and solvent-free method for the determination of nine chlorophenol (CP) compounds in honey samples using headspace solid-phase microextraction (HS-SPME) and gas chromatography with atomic emission detection (GC-AED) is developed. The different factors affecting the efficiency of the extraction and derivatization steps were carefully optimized. The polydimethylsiloxane-divinylbenzene (PDMS/DVB) fiber was the most suitable for preconcentrating the analytes from the headspace of an aqueous solution containing the dissolved honey samples where the chlorophenols had been submitted to acetylation. When the matrix effect was evaluated for different samples, it was concluded that standard addition calibration was required for quantification purposes. Detection limits roughly ranged from 0.1 to 2.4 ng g(-1), depending on the compound and the honey sample analyzed, with a fiber time exposure of only 15 min at 75 degrees C. The optimized method was successfully applied to different samples, some of the studied chlorophenols being detected in some of the analyzed honeys at concentration levels 0.6-9.4 ng g(-1).

Analysis of odorous trichlorobromophenols in water by in-sample derivatization/solid-phase microextraction GC/MS

The simultaneous determination of several odorous trichlorobromophenols in water has been carried out by an in-sample derivatization headspace solid-phase microextraction method (HS-SPME). The analytical procedure involved their derivatization to methyl ethers with dimethyl sulfate/NaOH and further HS-SPME and gas chromatography-mass spectrometry (GC/MS) determination. Parameters affecting both the derivatization efficiency and headspace SPME procedures, such as the selection of the SPME fiber coating, derivatization-extraction time and temperature, were studied. The commercially available polydimethylsiloxane (PDMS) 100 microm and Carboxen-polydimethylsiloxane-divinylbenzene (CAR-PDMS-DVB) fibers appeared to be the most suitable for the simultaneous determination of these compounds. The precision of the HS-SPME/GC/MS method gave good relative standard deviations (RSDs) run-to-run between 9% and 19% for most of them, except for 2,5-diCl-6-Br-phenol, 2,6-diCl-3-Br-phenol and-2,3,6-triBr-phenol (22%, 25% and 23%, respectively). The method was linear over two orders of magnitude, and detection limits were compound dependent but ranged from 0.22 ng/l to 0.95 ng/l. The results obtained for water samples using the proposed SPME procedure were compared with those found with the EPA 625 method, and good agreement was achieved. Therefore, the in-sample derivatization HS-SPME/GC/MS procedure here proposed is a suitable method for the simultaneous determination of odorous trichlorobromophenols in water.

Ethanol/Water extraction combined with solid-phase extraction and solid-phase microextraction concentration for the determination of chlorophenols in cork stoppers

The appearance of 2,4,6-trichloroanisole (TCA) in cork stoppers is of great concern because it can cause off-flavors in bottled wine. To prevent this sensorial defect, there should not be any traces of 2,4,6-trichlorophenol (TCP), 2,3,4,6-tetrachlorophenol (TeCP), or pentachlorophenol (PCP) in the finished corks, because they are the direct precursors of TCA. In the course of this study two methodologies based upon an extraction with ethanol/water mixtures to determine the chlorophenolic content in cork matrices were developed. The cork extract is preconcentrated using both solid-phase extraction and solid-phase microextraction methodologies. The latter was optimized by applying a full two-level factorial design. Finally, spiked ground corks at nanogram per gram levels of each chlorophenol were analyzed under optimal conditions and by applying both procedures. The obtained results demonstrate that chlorophenols can be detected in corks contaminated at the nanogram per gram level and, thus, these approaches can be successfully applied as quality control measures in the cork industry.

Quantification of chloroanisoles in cork using headspace solid-phase microextraction and gas chromatography with electron capture detection

Chloroanisoles can migrate from the cork stopper in wine bottles to the wine and give it a musty taint so it is important to find a method by which they can be determined. The aim of this paper is to develop a method for quantifying 2,4-dichloroanisole, 2,6-dichloroanisole, 2,4,6-trichloroanisole, 2,3,4,6-tetrachloroanisole and 2,3,4,5,6-pentachloroanisole in cork using headspace solid-phase microextraction and gas chromatography with electron capture detection. After we had prepared the cork standards that were so essential to the work we optimised the parameters that most influence headspace solid-phase microextraction: fibre coating, vial volume, cork, kind and volume of solvent to help the extraction, extraction temperature and time, ionic strength and stirring. The method quantifies the total amount of chloroanisoles in cork stoppers (natural, agglomerated, agglomerated with disks and sparkling wine stoppers), at suitable concentrations so that the capacity of these compounds to give wine a musty taint can be evaluated. The quantification limits are: 2,6-dichloroanisole (8.6 ng/g), 2,4,6-trichloroanisole (0.8 ng/g), 2,4-dichloroanisole (3.5 ng/g), 2,3,4,6-tetrachloroanisole (0.6 ng/g), 2,3,4,5,6-pentachloroanisole (0.8 ng/g). The other quality parameters are: recoveries (90.3-105.8%), repeatability (4-13% (RSD expressed)) and intermediate precision (5-14% (RSD expressed)).

Determination of trace concentrations of bromophenols in water using purge-and-trap after in situ acetylation

An analytical method that enables detection and quantification of bromophenols (BPs) at taste threshold concentrations (2,6-DBP: 0.5 ng/L) was developed. This method involves conversion of the BPs to their acetates, followed by isolation of the acetates by a modified purge-and-trap procedure, and analysis by gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring (SIM) mode. Bromophenyl acetates were synthesized so that each of the two steps in the method could be developed and optimised in isolation to the other. Deuterated BPs (phenol-d5, 2-BP-d4, 4-BP-d2, 2,6-DBP-d3, 2,4-DBP-d3 and 2,4,6-TBP-d2) were synthesized to enable quantification of analytes using the deuterated analogues of analytes as internal standards. This method allowed quantification of BPs at concentrations ranging from the detection limits (3 ng/L for phenol and 0.1-0.5 ng/L for each of the BPs) to 1000 ng/L for each analyte, with repeatabilities of < or =14% (RSD) for concentrations of 1 ng/L and < or =9% (RSD) for concentrations of 10-1000 ng/L, with recoveries ranging from 91 to 97%.

Detection of 2,4,6-trichloroanisole in chlorinated water at nanogram per litre levels by SPME–GC–ECD

A method involving solid-phase micro extraction (SPME) and gas chromatography with electron capture detection (SPME-GC-ECD) has been optimised for identification and quantification of 2,4,6-trichloroanisole (TCA) at ng L(-1) concentrations in disinfected (chlorinated) water samples. A central composite design was used for factorial analysis of four factors, three factors related to the SPME (PDMS fibre) procedure (adsorption time, temperature of the sample during headspace sampling, and desorption time) and one related to the GC operation (the rate of increase of the temperature of the GC oven). Good linearity (linear correlation coefficient greater than 0.999) was observed for TCA concentrations up to 50 ng L(-1), limits of detection and quantification of 0.7 and 2.3 ng L(-1), respectively, and good precision (relative standard deviation 2.8% and 3.4% for 5 and 30 ng L(-1) of TCA, respectively). Besides TCA, this system also enables the detection and quantification of the four trihalomethanes in the microg L(-1) concentration range with limits of detection and quantification of approximately 0.3 microg L(-1) and 1 microg L(-1), respectively.

Determination of odorous mixed chloro-bromoanisoles in water by solid-phase micro-extraction and gas chromatography–mass detection

A headspace-solid-phase micro-extraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) method has been proposed for the simultaneous determination of odorous trihalogenated anisoles in water. Parameters affecting efficiency of HS-SPME procedure, such as the selection of the SPME coating, extraction time, temperature and ionic strength were optimized. The commercially available polydimethylsiloxane (PDMS 100 microm) fiber appears to be the most suitable for the simultaneous determination of these compounds. Run-to-run precision with relative standard deviations (R.S.D.s) between 5 and 15% were obtained for most of the compounds except for 2,5-dicloro-6-bromo-anisole, 2,3-dibromo-6-chloroanisole, pentachloro- and pentabromoanisole (>20%). The method was linear over two orders of magnitude, and detection limits were compound dependent and ranged from 0.03 ng/L for 2,4,6-trichloroanisole to 0.25 ng/L for 2,3-dibromo-6-chloroanisole. The HS-SPME-GC-MS procedure was tested using real samples and relatively good standard deviations were obtained when using p-iodoanisole as internal standard for quantification. This is the first time that the individual identification of odorous trihalogenated chloro-bromoanisoles has been reported, being HS-SPME-GC-MS a suitable method for simultaneous determination of these compounds in water at concentration levels below their odor limit of detection.

Optimisation of a headspace solid-phase microextraction method for the direct determination of chloroanisoles related to cork taint in red wine

One of the most critical problems in the enological industry is associated with cork taint. The main compounds responsible for this off-flavour are some chloroanisoles: 2,4,6-trichloroanisole (TCA), 2,3,4,6-tetrachloroanisole (TECA) and pentachloroanisole (PCA). Headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography-electron capture detection has been used for the direct determination of these chloroanisoles in wine samples. After the evaluation of some parameters (desorption conditions and salt addition) that affect extraction efficiency, a screening study of six types of fibres and five extraction temperatures was performed. Then, a Doehlert matrix including the exposure time, temperature and Vs (sample volume)/Vt (total volume) ratio as experimental factors was proposed. According to the results of this design and the kinetic profiles evaluated, an analytical procedure based on HS-SPME was optimised and validated. This method can be used for the simultaneous determination at the low ng/l level of all chloroanisoles involved in cork taint, and not only TCA, which is the only compound found in the literature when SPME is proposed as the analytical technique.

Optimisation of the derivatisation reaction and subsequent headspace solid-phase microextraction method for the direct determination of chlorophenols in red wine

An acetylation reaction for the derivatisation of the three chlorophenols involved in cork taint was optimised using a Doehlert design for direct application in wine samples. In this first step, the optimum reaction pH, by adding different amounts of KHCO3, and the required quantity of derivatisation reagent were fixed. Then a series of parameters relevant for the headspace solid-phase microextraction process, such as desorption conditions, salt addition and agitation sample were evaluated. A simultaneous study of the type of fibre and extraction temperature was performed at five levels and based on the results obtained the rest of factors (sample volume and exposition time) that could potentially affect the extraction yields were optimised by a central composite design. According to the validation of the method, we propose here, to our knowledge, the first application of solid-phase microextraction for the direct analysis of chlorophenols in red wine samples.

Development of solid-phase extraction and solid-phase microextraction methods for the determination of chlorophenols in cork macerate and wine samples

Tri-, tetra- and pentachlorophenol (TCP, TeCP and PCP) can be considered the precursors in the formation of corresponding chloroanisoles, known to be powerful odorants in corks and wine. Determining the presence of these chlorophenolic compounds in cork soaking solutions (ethanol/water mixtures, 12% (v/v) ethanol used for cork quality control testing), or in wine can be achieved by acetylation/gas chromatography electron-capture detection. In order to reach the required sensitivity, a previous preconcentration step is necessary. Solid-phase extraction (SPE) and headspace solid-phase microextraction (HS-SPME) have given good results for the preconcentration of TCP, TeCP and PCP in such matrices. The use of Oasis HLB cartridges gives acceptable recoveries for the three compounds when different volumes (50-250 mL) of cork macerate with concentrations ranging from 20 to 150 ng/L are processed. Preconcentration based on HS-SPME has also been optimised with a 100 microm polydimethylsiloxane fibre and in situ derivatization. The HS-SPME method allows chlorophenols in a cork soaking solution and in wine to be determined with a limit of detection of 1 ng/L for each compound (in cork macerate) and a repeatability of around 0.5%-5% (n=8) for a concentration level of 30 ng/L.

Identification of 2,3-butanedione (diacetyl) as the compound causing odor events at trace levels in the Llobregat River and Barcelona’s treated water (Spain)

A study of organic compounds imparting sweet and buttery odor problems in the Llobregat River (northeast Spain) and in treated water was conducted. Solid-phase microextraction (SPME), gas chromatography-olfactometry, and flavor profile analysis (FPA) were used as analytical methodologies to identify the compound responsible for odor incidents. 2,3-Butanedione (diacetyl) with a concentration range of 0.90-26 microg/l in river water samples entering the water treatment plant was identified as the compound causing the odor events. Flavor profile analysis establishes 0.05 microg/l as its odor threshold concentration (OTC) in water, with an odor recognition concentration of 0.20 microg/l. The analyses were carried out with SPME-GC-MS and parameters affecting SPME extraction such as selection of the fiber (carboxen-polydimethylsiloxane), extraction time (30 min), temperature (60 degrees C), and ionic strength were evaluated. Quality parameters of the optimized method gives good linearity (r2 > 0.999), a limit of detection (0.08 microg/l) similar to the OTC of the compound, and good reproducibility (R.S.D. < 20%). The SPME method was applied to identify the compound causing the odor.