On-line monitoring trihalomethanes in chlorinated water by membrane introduction-fast gas chromatography mass-spectrometry

An analytical method based on membrane introduction and fast gas chromatography-mass spectrometry (GC-MS) has been developed for the on-line monitoring of trihatomethanes (THMs) in chlorinated drinking water. The coupling of membrane introduction with fast GC-MS offers the advantage of membrane introduction as an on-line sampling device and fast GC-MS as a separation and identification method. While maintaining the on-line monitoring characteristic of traditional membrane introduction mass spectrometry (MIMS), the difficulty of distinguishing CHCl3 and CHBrCl2 in MIMS was overcome by rapid GC separation and MS analysis. Water permeated across the membrane affected the analysis of CHBr2Cl and CHBr3. A method based on controlling the injection temperature and injection time has been developed to overcome the moisture problem. This method is simple and less time consuming than the conventional moisture removing method. Under typical operating conditions, the sampling rate was about 20 samples h(-1) capable of on-line monitoring THMs in chlorinated drinking water. The detection limits of this system were found to be about 2 ppt, 4 ppt, 4 ppt, and 8 ppt for CHCl3 CHBrCl2, CHBr2Cl, and CHBr3, respectively.     

Theoretical limiting concentration for mineralization of trichloromethane and dichloromethane in aqueous solutions by AOPs

It is widely stated that most organic contaminants could be completely mineralized by Advanced Oxidation Processes(AOPs). This statement means that the concentration of the organic contaminant at equilibrium(limiting concentration,LC)is low enough to be neglected.However,for environmental safety,especially drinking water safety,this statement needs to be verified from chemical engineering thermodynamic analysis.In this paper,trichloromethane(CHCl3)and dichloromethane(CH2Cl2) are selected as the model system...     

Rapid determination of total trihalomethanes index in drinking water

A method for the rapid determination of total trihalomethanes (THMs) index in drinking water has been developed by using a headspace-mass spectrometry (HS-MS) system and partial least squares (PLS) multivariate regression approach. Due to the presence of residual amounts of chlorine and organic matter in the drinking water, the use of a quenching reagent in order to avoid THM generation during the sample manipulation is necessary. The optimization experiments revealed that ascorbic acid was the best quenching reagent compared with sodium thiosulfate and ammonium sulfate. The use of a classification chemometric technique as soft independent modeling of class analogy before the PLS regression improved the results obtained in the prediction of the total THMs index, lowering the relative standard error of prediction (RSEP) from 11.4% to lower than 6.0%. The results obtained by the proposed HS-MS method were compared with those provided by a conventional chromatographic method after analyzing 20 real drinking water samples. A good agreement in the results was observed and no systematic differences were found, which corroborates the good performance of the proposed method.     

Towards minimization of chlorinated solvents consume in Fourier transform infrared spectroscopy determination of Propamocarb in pesticide formulations

A method has been developed for Fourier transform infrared (FTIR) spectroscopy determination of Propamocarb in emulsifiable pesticide concentrate formulations. Five microliter sample was directly injected without any pretreatment in a CHCl3 stream at 2 mL min(-1) into a closed system and the FTIR spectra of sample and standard solutions were obtained using a nominal resolution of 4 cm(-1) from 4000 to 900 cm(-1) spectral region and accumulating 2 scans per spectrum. Propamocarb determination was based on the measurement of flow injection analysis (FIA) recording height established from FTIR peak area measurements from 1713 to 1703 cm(-1) corrected using a baseline defined at 2000 cm(-1). The concentration of Propamocarb in samples was calculated by interpolation in an external calibration line obtained from several injections of 2 microL of a 47% (w/v) standard solution into the CHCl3 closed system. This procedure provided a limit of detection of 0.8% (w/v) in the original sample, a sensitivity of 0.3190 absorbance units mL mg(-1) for a path length of 0.11 mm and a relative standard deviation of 0.2% for five independent measurements at 0.74 mg mL(-1) concentration level. The maximum sampling frequency of the whole procedure was 34 h(-1) and the waste generation was reduced to only 2 mL of CHCl3 solution per sample and additional 2 mL for the whole calibration line.     

On‐line monitoring of the dynamics of trihalomethane concentrations in a warm public swimming pool using an unsupervised membrane inlet mass spectrometry system with off‐site real‐time surveillance

To study the long‐term dynamics of trihalomethanes (THMs) in a warm (31–33°C) public swimming pool, we built a robust membrane inlet mass spectrometer that could perform unsupervised, on‐site monitoring of the concentration of these compounds with off‐site, real‐time surveillance. The instrument was installed in a technical room below the pool and operated continuously for more than a year practically only interrupted for filament replacements every 6–8 weeks. One to two days after a filament replacement, the instrument stabilized and kept its calibration until shortly before the next filament burnout. The on‐line monitoring of THMs revealed a daily rhythm in the concentrations of chloroform and bromodichloromethane. They increased during the pool's closing hours and decreased during opening hours with the minimum concentration being approximately half of the maximum. Over the 1 year monitoring period, the variation in the maximum registered daily concentration was 30–100 µg/L for chloroform. The variation of bromodichloromethane was 5–10 µg/L, except during bursts of 1–2 days duration, where the concentration of bromodichloromethane could reach 100 µg/L. The burst in bromodichloromethane concentration was directly correlated with salt addition (sodium chloride) to the pool water for use in the pool's electrolytic in‐line chlorination system. A correlation between THM removal from the pool water and the operation of a strong water jet system was also found. Copyright © 2009 John Wiley & Sons, Ltd.     

Sample Preparation Methods for the Determination of Chlorination Disinfection Byproducts in Water Samples

Chlorination has been widely used as a disinfection method for control of pathogens in drinking water and wastewater treatment plants. Chlorination disinfection byproducts (DBPs) are formed when organic matter is present in water, and they are harmful to human health. The main groups of compounds formed are trihalomethanes (THMs), haloacetic acids (HAAs) and haloacetonitriles (HANs). Analysis of THMs, HAAs and HANs in water samples has been reported. This paper reviews the various sample preparation methods in use for analysis of THMs, HAAs and HANs in water samples.

     

Pressure-assisted electrokinetic injection for on-line enrichment in capillary electrophoresis-mass spectrometry: a sensitive method for measurement of ten haloacetic acids in drinking water

Haloacetic acids (HAAs) are by-products of the chlorination of drinking water containing natural organic matter and bromide. A simple and sensitive method has been developed for determination of ten HAAs in drinking water. The pressure-assisted electrokinetic injection (PAEKI), an on-line enrichment technique, was employed to introduce the sample into a capillary electrophoresis (CE)–electrospray ionization–tandem mass spectrometry system (ESI-MS/MS). HAAs were monitored in selected reaction monitoring mode. With 3 min of PAEKI time, the ten major HAAs (HAA10) in drinking water were enriched up to 20,000-fold into the capillary without compromising resolution. A simple solid phase clean-up method has been developed to eliminate the influence of ionic matrices from drinking water on PAEKI. Under conditions optimized for mass spectrometry, PAEKI and capillary electrophoresis, detection limits defined as three times ratio of signal to noise have been achieved in a range of 0.013–0.12 μg L⁻¹ for ten HAAs in water sample. The overall recoveries for all ten HAAs in drinking water samples were between 76 and 125%. Six HAAs including monochloro- (MCAA), dichloro- (DCAA), trichloro- (TCAA), monobromo- (MBAA), bromochloro- (BCAA), and bromodichloroacetic acids (BDCAA) were found in tap water samples collected.     

On-line monitoring of trihalomethane concentrations in drinking water distribution systems using capillary membrane sampling-gas chromatography

Trihalomethane concentrations are not typically monitored continuously in drinking water distribution systems. This means that data is not immediately available to operators so that they can make decisions that directly affect water quality. Monitoring data could be useful to researchers and operators who might want to better understand disinfection by-product formation and removal in their distribution systems. In this paper, a capillary membrane sampler (CMS), which uses a silicone membrane to directly sample trihalomethanes from a water sample, shows promise as a sampling device that can be used to introduce samples directly into a gas chromatograph for on-line monitoring. The construction, optimization, operation and evaluation of this capillary membrane sampling-gas chromatograph (CMS-GC) are discussed. The result of optimization, method detection limit, accuracy, precision and linearity studies are presented. Side-by-side studies have been done comparing the CMS-GC method to USEPA Method 502.2. While the CMS-GC method is not meant to replace USEPA Method 502.2, it does offer advantages for on-line monitoring and meets several of the criteria proposed as desirable for on-line monitoring of THM concentrations in drinking water distribution systems.     

Determination of Trihalomethanes in Drinking Water by Dispersive Liquid–Liquid Microextraction then Gas Chromatography with Electron-Capture Detection

Dispersive liquid–liquid microextraction (DLLME) has been used for preconcentration of trihalomethanes (THMs) in drinking water. In DLLME an appropriate mixture of an extraction solvent (20.0 μL carbon disulfide) and a disperser solvent (0.50 mL acetone) was used to form a cloudy solution from a 5.00-mL aqueous sample containing the analytes. After phase separation by centrifugation the enriched analytes in the settled phase (6.5 ± 0.3 μL) were determined by gas chromatography with electron-capture detection (GC–ECD). Different experimental conditions, for example type and volume of extraction solvent, type and volume of disperser solvent, extraction time, and use of salt, were investigated. After optimization of the conditions the enrichment factor ranged from 116 to 355 and the limit of detection from 0.005 to 0.040 μg L⁻¹. The linear range was 0.01–50 μg L⁻¹ (more than three orders of magnitude). Relative standard deviations (RSDs) for 2.00 μg L⁻¹ THMs in water, with internal standard, were in the range 1.3–5.9% (n = 5); without internal standard they were in the range 3.7–8.6% (n = 5). The method was successfully used for extraction and determination of THMs in drinking water. The results showed that total concentrations of THMs in drinking water from two areas of Tehran, Iran, were approximately 10.9 and 14.1 μg L⁻¹. Relative recoveries from samples of drinking water spiked at levels of 2.00 and 5.00 μg L⁻¹ were 95.0–107.8 and 92.2–100.9%, respectively. Comparison of this method with other methods indicates DLLME is a very simple and rapid (less than 2 min) method which requires a small volume of sample (5 mL).     

A simple supported liquid hollow fiber membrane microextraction for sample preparation of trihalomethanes in water samples

A simple and efficient liquid-phase microextraction (LPME) technique using a supported liquid hollow fiber membrane, in conjunction with gas chromatography-electron capture detector has been developed for extraction and determination of trihalomethanes (THMs) in water samples. THMs were extracted from water samples through an organic extracting solvent impregnated in the pores and filled inside the porous hollow fiber membrane. Our simple conditions were conducted at 35 degrees C with no stirring and no salt addition in order to minimize sample preparation steps. Parameters such as types of hollow fiber membranes, extracting solvents and extraction time were studied and optimized. The method exhibited enrichment factors ranged from 28- to 62-fold within 30 min extraction time. The linearity of the method ranged from 0.2 to 100 microg l(-1). The limits of detection were in the low microg l(-1) level, ranging between 0.01 and 0.2 microg l(-1). The recoveries of spiked THMs at 5 microg l(-1) in water were between 98 and 105% with relative standard deviations (RSDs) less than 4%. Furthermore, the method was applied for determination of THMs in drinking water and tap water samples was reported.     

Fast separation of UV absorbing anions using ion-interaction chromatography

Ion-interaction chromatography on a short (30 x 4.6 mm) 3 microm ODS column has been investigated with the aim of developing fast chromatographic separations of selected inorganic anions. Tetrabutylammonium chloride (TBA-Cl) was used as the ion-interaction reagent in mobile phases that also contained up to 20% methanol. Separations of simple test mixtures of up to eight UV absorbing anions illustrated how excellent efficiencies (>50,000 plates/m) could be obtained under optimized conditions. The use of an optimised mobile phase containing 20 mM TBA-Cl and 20% methanol resulted in the baseline separation of five important anions (iodate, bromate, nitrite, bromide and nitrate) in a separation window of just 28 s, with a shortest total analysis time of 50 s. The method was briefly applied to the rapid analysis of nitrite and nitrate in both a drinking water and a river water sample with a view to future on-line monitoring.     

Concentration of volatile organic compounds from solvents by sustained chromatographic evaporation

A system for quantitative concentration of volatile organic trace compounds present in organic solvents is described. Evaporation of the solvent is carried out inside a glass capillary tube by the action of a carrier gas, and large volumes can be reduced by a repeated sample injection and a cyclic flow reversal. Best recovery is obtained when a barrier of pure solvent is maintained ahead of the sample during concentration. Four rotary valves are employed for sample and solvent injection and direction of the gas flow. In principle, indefinite sample volumes can be handled, the limit being set by system contaminants. The process was evaluated both off-line and on-line to a gas chromatograph. Concentration of compounds like methylcyclopentane, hexane, and cyclohexane present in pentane in the low nanogram range and subsequent on-line transfer to a gas chromatograph could be performed with a quantitative recovery. The technique was applied to analysis of trace volatiles in drinking water. Detection limits were estimated to be approximately 0.02 ng/L for normal hydrocarbons (FID detection) when concentration of a pentane extract from a one litre water sample was carried out.     

Measurement of trihalomethanes and methyl tertiary-butyl ether in tap water using solid-phase microextraction GC-MS

The prevalence of water disinfection byproducts in drinking water supplies has raised concerns about possible health effects from chronic exposure to these compounds. To support studies exploring the relation between exposure to trihalomethanes (THMs) and health effects, we have developed an automated analytical method using headspace solid-phase microextraction coupled with capillary gas chromatography and mass spectrometry. This method quantitates trace levels of THMs (chloroform, bromodichloromethane, dibromochloromethane, and bromoform) and methyl tertiary-butyl ether in tap water. Detection limits of less than 100 ng/L for all analytes and linear ranges of three orders of magnitude are adequate for measuring the THMs in tap water samples tested from across the United States. THMs are stable for extended periods in tap water samples after quenching of residual chlorine and buffering to pH 6.5, thus enabling larger epidemiologic field studies with simplified sample collection protocols.     

Sequential-injection on-line preconcentration using chitosan resin functionalized with 2-amino-5-hydroxy benzoic acid for the determination of trace elements in environmental water samples by inductively coupled plasma-atomic emission spectrometry

A new chelating resin using chitosan as a base material was synthesized. Functional moiety of 2-amino-5-hydroxy benzoic acid (AHBA) was chemically bonded to the amino group of cross-linked chitosan (CCTS) through the arm of chloromethyloxirane (CCTS-AHBA resin). Several elements, such as Ag, Be, Cd, Co, Cu, Ni, Pb, U, V, and rare earth elements (REEs), could be adsorbed on the resin. To use the resin for on-line pretreatment, the resin was packed in a mini-column and installed into a sequential-injection/automated pretreatment system (Auto-Pret System) coupled with inductively coupled plasma-atomic emission spectrometry (ICP-AES). The sequential-injection/automated pretreatment system was a laboratory-assembled, and the program was written using Visual Basic software. This system can provide easy operation procedures, less reagent consumption, as well as less waste production.

Experimental variables considered as effective factors in the improvement sensitivity, such as an eluent concentration, a sample and an eluent flow rate, pH of samples, and air-sandwiched eluent were carefully optimized. The proposed system provides excellent on-line collection efficiency, as well as high concentration factors of analytes in water samples, which results in highly sensitive detection of ultra-trace and trace analysis. Under the optimal conditions, the detection limits of 24 elements examined are in the range from ppt to sub-ppb levels. The proposed method was validated by using the standard reference material of a river water, SLRS-4, and the applicability was further demonstrated to the on-line collection/concentration of trace elements, such as Ag, Be, Cd, Co, Cu, Ni, Pb, U, V, and REEs in water samples.     

New derivatization method for determination of 3-chloro-4(dichloromethyl)-5-hydroxy-2(5H)-furanone in water

An extremely potent mutagen, 3-chloro-4(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) is commonly present in chlorinated drinking water. Due to its high mutagenic activity and according to World Health Organization guidelines its concentration should be controlled in drinking waters. Determination of MX is difficult due to ppt levels at which the compound usually exists in drinking waters. Derivatization of MX with 2-propanol is presented as a method which significantly lowers the GC–MS detection level compared to other alcohol derivatization agents.     

Rapid on-line preconcentration and suppressed micro-bore ion chromatography of part per trillion levels of perchlorate in rainwater samples

The development of a rapid method for the determination of perchlorate in rain and drinking waters is presented. In the optimised method, an on-line preconcentration technique was employed utilising a 10 mm × 4.6 mm Phenomenex Onyx monolithic guard cartridge coated with (N-dodecyl-N,N-dimethylammonio)undecanoate for selective preconcentration, with subsequent elution into a fixed volume injection loop (‘heart-cut’ of the concentrator column eluate) and separation using an IonPac AS16 (250 mm × 2 mm) anion exchange column and a potassium hydroxide concentration gradient. Off-line optimisation studies showed that the coated monolith displayed near quantitative recovery up to 50 μg/L perchlorate level from standards prepared in reagent water. On-line preconcentration of perchlorate obtained detection limits down to 56 ng/L in reagent water, between 70 and 80 ng/L in rainwater samples and 2.5 μg/L in non-pretreated drinking water. After an additional sample sulphate/carbonate removal step, low ng/L perchlorate concentrations could also be observed in drinking water. The complete on-line method exhibited reproducibility for n = 10 replicate runs of R.S.D. ≤ 3% for peak height/area and R.S.D. = 0.08% for retention time. The optimised method, of 20 min total duration, was applied to the determination of perchlorate by standard addition in 10 rainwater samples and one drinking water sample. Concentrations of perchlorate present ranged from below the detection limit for four rainwater samples, with another three samples showing perchlorate present at between 70 and 100 ng/L, and one sample showing perchlorate present at 2.8 μg/L. Levels of 1.1 μg/L in the drinking water sample were also recorded.     

Determination of polar aniline derivatives in aqueous environmental samples using on-line liquid chromatographic preconcentration techniques

Summary On-line precolumn sample handling is used to enrich polar aniline derivatives in order to preconcentrate them prior to their separation. Liquid-solid extraction is possible with a cation-exchanger precolumn after acidification of water samples at pH 3 and a clean-up in order to remove the high amounts of inorganic cations present in natural samples. Since inorganic removal cannot be total, overloading of the ion exchanger occurs rapidly. The volume which can be directly percolated through the cation-exchanger precolumn cannot exceed 30 ml and the amount preconcentrated is not sufficient for a determination at the 100 ppt level. A two-step preconcentration procedure is carried out in order to increase the sample volume: the direct percolation of samples through the cation-exchanger precolumn is avoided and the clean-up step is no longer necessary. Aniline derivatives are preconcentrated in their neutral form at pH 7 by a 9-cm long column packed with the copolymer-based PRP-1 sorbent; then, a small volume of water-methanol at pH 2 allows the cationic compounds alone to be desorbed from the PRP-1 column in their protonated form and to be transferred to a 1-cm long cation-exchanger precolumn. This precolumn is then coupled to an analytical C18 column and its content on-line analysed by an acetonitrile gradient. The PRP-1 column acts as a powerful filter to many neutral interferents and aniline derivatives can be thus determined from 150-ml drinking water samples with 10–50 ppt UV detection limits.Dedicated to Roland W. Frei     

Determination of As(III) and total inorganic arsenic by flow injection hydride generation atomic absorption spectrometry

A simple procedure was developed for the direct determination of As(III) and As(V) in water samples by flow injection hydride generation atomic absorption spectrometry (FI–HG–AAS), without pre-reduction of As(V). The flow injection system was operated in the merging zones configuration, where sample and NaBH₄ are simultaneously injected into two carrier streams, HCl and H₂O, respectively. Sample and reagent injected volumes were of 250 μl and flow rate of 3.6 ml min⁻¹ for hydrochloric acid and de-ionised water. The NaBH₄ concentration was maintained at 0.1% (w/v), it would be possible to perform arsine selective generation from As(III) and on-line arsine generation with 3.0% (w/v) NaBH₄ to obtain total arsenic concentration. As(V) was calculated as the difference between total As and As(III). Both procedures were tolerant to potential interference. So, interference such as Fe(III), Cu(II), Ni(II), Sb(III), Sn(II) and Se(IV) could, at an As(III) level of 0.1 mg l⁻¹, be tolerated at a weight excess of 5000, 5000, 500, 100, 10 and 5 times, respectively. With the proposed procedure, detection limits of 0.3 ng ml⁻¹ for As(III) and 0.5 ng ml⁻¹ for As(V) were achieved. The relative standard deviations were of 2.3% for 0.1 mg l⁻¹ As(III) and 2.0% for 0.1 mg l⁻¹ As(V). A sampling rate of about 120 determinations per hour was achieved, requiring 30 ml of NaBH₄ and waste generation in order of 450 ml. The method was shown to be satisfactory for determination of traces arsenic in water samples. The assay of a certified drinking water sample was 81.7±1.7 μg l⁻¹ (certified value 80.0±0.5 μg l⁻¹).     

Clean-up of some organochlorine and pyrethroid insecticides by automated solid-phase extraction cartridges coupled to capillary GC-ECD

The ASPEC (Automatic Sample Preparation with Extraction Columns) system has been coupled on-line to capillary GC-ECD by means of a loop-type interface equipped with a solvent vapour exit. Both ASPEC and GC conditions have been optimized leading to an effective clean-up of the extracts analyzed. By means of solid-phase extraction cartridges filled with silica, it has been possible to analyze concentrated surface water extracts for a group of 18 electron-capturing compounds present in the water at ppt levels. ASPEC-GC has also been applied to the determination of synthetic pyrethroids at ppt levels in surface water. The complete analytical procedure is greatly facilitated by automation and miniaturization. Miniaturization results in a considerable decrease in the sample volume required. The potential of the method for the analysis of other pesticides is estimated.     

臭氧化对水厂水中消毒副产物生成势的影响

以某饮用水厂沿程工艺出水为研究对象,研究了臭氧化预处理对水体中消毒副产物(DBPs)氯化生成势的影响。结果表明,水厂生物处理单元产生的胞外聚合物(EPS)和溶解性微生物产物(SMP)等生物源有机物是非常有效的DBPs前体物,但其更易于氯化生成三卤甲烷(THMs)而非卤乙酸(HAAs)。水厂水中存在的THMs前体物主要是各类大分子量有机物,并且臭氧工艺对其有较好的氧化去除效果。水厂水中经臭氧氧化产生的小分子量有机物可能是更为有效的一氯乙酸(MCAA)和一溴乙酸(MBAA)前体物。此外,当水体中三氯乙酸(TCAA)前体物浓度较高时,臭氧工艺对TCAA生成势具有很好的去除效果。