Determination of trace levels of haloacetic acids and perchlorate in drinking water by ion chromatography with direct injection

Disinfection by products of haloacetic acids and perchlorate pose significant health risks, even at low microg/l levels in drinking water. A new method for the simultaneous determination of nine haloacetic acids (HAAs) and perchlorate as well as some common anions in one run with ion chromatography was developed. The HAAs tested included mono-, di-, trichloroacetic acids, mono, di-, tribromoacetic acids, bromochloroacetic acid, dibromochloroacetic acid, and bromodichloroacetic acid. Two high-capacity anion-exchange columns, a carbonate-selective column and a hydroxide-selective hydrophilic one, were used for the investigation. With the carbonate-selective column, the nine HAAs as well as fluoride, chloride, nitrite, nitrate, phosphate and sulfate could be well separated and determined in one run. With the very hydrophilic column and a gradient elution of sodium hydroxide, methanol and deionized water, the nine HAAs, fluoride, chloride, nitrite, nitrate as well as perchlorate could be simultaneously determined in one run within 34 min. The detection limits for HAAs were between 1.11 and 9.32 microg/l. For perchlorate, it was 0.60 microg/l.     

固相萃取-离子色谱法测定饮用水中的痕量卤代乙酸

建立了固相萃取-离子色谱(SPE-IC)测定饮用水中痕量卤代乙酸(HAAs)(包括一氯乙酸、二氯乙酸、三氯乙酸、一溴乙酸和二溴乙酸)的方法。固相萃取采用LiChrolut EN SPE柱来进行痕量待测物的预浓缩（25倍）和基体杂质的消除,用NaOH(10 mmol/L)洗脱;色谱分离采用亲水性、高容量、氢氧化物选择型阴离子交换柱Dionex IonPac AS16(250 mm×4 mm i.d.),以NaOH为流动相进行浓度梯度淋洗,淋洗速度为0.8 mL/min,电导检测,进样量为500 μL。结果表明,用SPE-IC法测定HAAs,一溴乙酸的检测限为12.5 μg/L,其余4种HAAs的检测限为0.38~1.69　μg/L。该法可实现对饮用水中痕量卤代乙酸的测定。     

Determination of trace-level haloacetic acids in drinking water by ion chromatography-inductively coupled plasma mass spectrometry

A new method for the determination of nine haloacetic acids (HAAs) with ion chromatography (IC) coupled to inductively coupled plasma mass spectrometry (ICP-MS) was developed. With the very hydrophilic anion-exchange column and steep gradient of sodium hydroxide, the nine HAAs could be well separated in 15 min. After suppression with an ASRS suppressor that was introduced in between IC and ICP-MS, the background was much decreased, the interference caused by sodium ion present in eluent was removed, and the sensitivities of HAAs were greatly improved. The chlorinated and brominated HAAs could be detected as 35ClO and 79Br without interference of the matrix due to the elemental selective ICP-MS. The detection limits for mono-, di-, trichloroacetic acids were between 15.6 and 23.6 microg/l. For the other six bromine-containing HAAs, the detection limits were between 0.34 and 0.99 microg/l. With the pretreatment of OnGuard Ag cartridge to remove high concentration of chloride in sample, the developed method could be applied to the determination of HAAs in many drinking water matrices.     

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.

     

Improved gas chromatography methods for micro-volume analysis of haloacetic acids in water and biological matrices

A fast headspace solid-phase microextraction gas chromatography method for micro-volume (0.1 mL) samples was optimized for the analysis of haloacetic acids (HAAs) in aqueous and biological samples. It includes liquid-liquid microextraction (LLME), derivatization of the acids to their methyl esters using sulfuric acid and methanol after evaporation, followed by headspace solid-phase microextraction with gas chromatography and electron capture detection (SPME-GC-ECD). The derivatization procedure was optimized to achieve maximum sensitivity using the following conditions: esterification for 20 min at 80 degrees C in 10 microL methanol, 10 microL sulfuric acid and 0.1 g anhydrous sodium sulfate. Multi-point standard addition method was used to determine the effect of the sample matrix by comparing with internal standard method. It was shown that the effect of the matrix for urine and blood samples in this method is insignificant. The method detection limits are in the range of 1 microg L(-1) for most of the HAAs, except for monobromoacetic acid (MBAA) (3 microg L(-1)) and for monochloroacetic acid (MCAA) (16 microg L(-1)). The optimized procedure was applied to the analysis of HAAs in water, urine and blood samples. All nine HAAs can be separated in < 13 min for biological samples and < 7 min for drinking water samples, with total sample preparation and analysis time < 50 min. Analytical uncertainty can increase dramatically as the sample volume decreases; however, similar precision was observed with our method using 0.1 mL samples as with a standard method using 40 mL samples.     

饮用水中9种卤乙酸的超高效液相色谱法测定

建立了固相萃取/超高效液相色谱(SPE/UPLC)测定饮用水中9种痕量卤乙酸(HAAs)的分析方法.对固相萃取和液相色谱等分析条件进行了优化,选择Lichrolut EN固相萃取小柱富集饮用水中的HAAs,三乙胺-磷酸缓冲液和甲醇作为UPLC的流动相.在优化的分析条件下,9种卤乙酸在6min内实现基线分离,所有目标物在一定质量浓度范围内线性良好,相关系数为0.995 7～0.9999;一氯乙酸(MCAA)的检出限为10.85μg/L,其它8种化合物的检出限为0.25～0.70μg/L;除MCAA外,其它目标物在低、中、高3种加标水平的回收率为60%～106%.方法的相对标准偏差(RSD,n=5)为2.0%～5.7%.将此方法应用于我国北方某城市自来水中卤乙酸的测定,5种HAAs被检出.方法灵敏度高、简便快捷,可用于生活饮用水中痕量卤乙酸的测定.     

Solid-phase microextraction coupled with gas chromatography-ion trap mass spectrometry for the analysis of haloacetic acids in water

Headspace solid-phase microextraction (SPME) was studied as a possible alternative to liquid-liquid extraction for the analysis of haloacetic acids (HAAs) in water. The method involves derivatization of the acids to their ethyl esters using sulphuric acid and ethanol after evaporation, followed by headspace SPME with a polydimethylsiloxane fibre and gas chromatography-ion trap mass spectrometry (GC-IT-MS). The derivatization procedure was optimized: maximum sensitivity was obtained with esterification for 10 min at 50 degrees C in 30 microl of sulphuric acid and 40 microl of ethanol. The headspace SPME conditions were also optimized and good sensitivity was obtained at a sampling temperature of 25 degrees C, an absorption time of 10 min, the addition of 0.1 g of anhydrous sodium sulfate and a desorption time of 2 min. Good precision (RSD lower than 10%) and detection limits in the ng l(-1) range (from 10 to 200 ng l(-1)) were obtained for all the compounds. The optimized procedure was applied to the analysis of HAAs in tap water and the results obtained by standard addition agreed with those of EPA method 552.2, whereas discrepancies due to matrix interferences were observed using external calibration. Consequently, headspace SPME-GC-IT-MS with standard addition is recommended for the analysis of these compounds in drinking water.     

Simultaneous liquid-liquid microextraction/methylation for the determination of haloacetic acids in drinking waters by headspace gas chromatography

A novel analytical method that combines simultaneous liquid-liquid microextraction/methylation and headspace gas chromatography-mass spectrometry for the determination of nine haloacetic acids (HAAs) in water was reported. A mechanistic model on the basis of mass transfer with chemical reaction in which methylation of HAAs was accomplished in n-pentane-water (150 microl-10 ml) two-phase system with a tetrabutylammonium salt as phase transfer catalyst was proposed. Derivatisation with dimethylsulphate was completed in 3 min by shaking at room temperature. The methyl ester derivatives and the organic phase were completely volatilised by static headspace technique, being the gaseous phase analysed. Parameters related to the extraction/methylation and headspace generation of HAAs were studied and the results were compared with methyl haloacetate standards to establish the yield of each step. The thermal instability of HAAs, by degradation to their respective halogenated hydrocarbon by decarboxylation, and the possible hydrolysation of the methyl esters were rigorously controlled in the whole process to obtain a reliable and robust method. The proposed method yielded detection limits very low which ranges from 0.02 to 0.4 microg l(-1) and a relative standard deviation of ca. 7.5%. Finally, the method was validated with the US Environmental Protection Agency (EPA) method 552.2 for the analysis of HAAs in drinking and swimming pool water samples containing concentrations of HAAs that must be higher than 10 microg l(-1) due to the fact that this method is less sensitive than the proposed one.     

反相固相萃取/超高效液相色谱-串联四极杆质谱仪同时测定污水中9种卤乙酸的方法研究

使用反相固相萃取预处理与超高效液相色谱-串联四极杆质谱仪(RSPE UPLC-MS/MS)联用建立了同时测定污水中9种卤乙酸(HAAs)的分析方法。研究表明:ENVI-C18固相萃取小柱能有效去除污水样品中有机基质的干扰,样品pH值调至2.5能有效消除无机离子对HAAs离子化的影响;采用HSST3(2.1 mm×100 mm)色谱柱,以甲醇和0.000 5%甲酸为流动相,可在15.0 min内将9种HAAs分离且效果良好。采用优化后的程序建立标准曲线,9种HAAs的线性范围为0.5~100μg/L,相关系数(r2)为0.999 7~0.999 9,检出限和定量下限分别为0.02~0.26μg/L和0.05~0.86μg/L,日内和日间相对标准偏差分别为1.4%~10.0%和1.7%~10.0%。3个污水处理厂出水在2.5μg/L和10μg/L的加标浓度水平下,回收率为85.2%~107.8%。该方法能够满足污水处理厂出水中9种HAAs的检测要求。     

In situ derivatization and hollow fiber membrane microextraction for gas chromatographic determination of haloacetic acids in water

An alternative method for gas chromatographic determination of haloacetic acids (HAAs) in water using direct derivatization followed by hollow fiber membrane liquid-phase microextraction (HF-LPME) has been developed. The method has improved the sample preparation step according to the conventional US EPA Method 552.2 by combining the derivatization and the extraction into one step prior to determination by gas chromatography electron captured detector (GC-ECD). The HAAs were derivatized with acidic methanol into their methyl esters and simultaneously extracted with supported liquid hollow fiber membrane in headspace mode. The derivatization was attempted directly in water sample without sample evaporation. The HF-LPME was performed using 1-octanol as the extracting solvent at 55 °C for 60 min with 20% Na₂SO₄. The linear calibration curves were observed for the concentrations ranging from 1 to 300 μg L⁻¹ with the correlation coefficients (R²) being greater than 0.99. The method detection limits of most analytes were below 1 μg L⁻¹ except DCAA and MCAA that were 2 and 18 μg L⁻¹, respectively. The recoveries from spiked concentration ranged from 97 to 109% with %R.S.D. less than 12%. The method was applied for determination of HAAs in drinking water and tap water samples. The method offers an easy one step high sample throughput sample preparation for gas chromatographic determination of haloacetic acids as well as other contaminants in water.     

Trace determination of nine haloacetic acids in drinking water by liquid chromatography–electrospray tandem mass spectrometry

A simple, fast and sensitive liquid chromatography–electrospray tandem mass spectrometry method was established for trace levels of nine haloacetic acids (HAAs) in drinking water. Water samples were removed of residual chlorine by adding l-ascorbic acid, and directly injected after filtered by 0.22 μm membrane. Nine HAAs were separated by liquid chromatography in 7.5 min, and the limits of detection were generally between 0.16 and 0.99 μg/L except for chlorodibromoacetic acid (1.44 μg/L) and tribromoacetic acid (8.87 μg/L). The mean recoveries of nine target compounds in spiked drinking water samples were 80.1–108%, and no apparent signal suppression was observed. Finally, this method was applied to determine HAAs in the tap water samples collected from five waterworks in Shandong, China. Nine HAAs except for monochloroacetic acid, monobromoacetic acid, dibromochloroacetic acid and tribromoacetic acid were detected, and the total concentrations were 7.79–36.5 μg/L. The determination results well met the first stage of the Disinfectants/Disinfection By-Products (D/DBP) Rules established by U.S.EPA and Guidelines for Drinking-water Quality of WHO.     

Supported liquid membrane microextraction with high-performance liquid chromatography-UV detection for monitoring trace haloacetic acids in water

Supported liquid membrane microextraction (SLMME) with high-performance liquid chromatography (HPLC)-UV detection has been developed for the extraction, preconcentration, and determination of all the nine haloacetic acids (HAAs) in water. The HAAs are extracted into a supported liquid membrane, and then back-extracted into few microliters of an acceptor solution. The extract was directly analyzed by HPLC-UV with a 15-min run. Enrichment factors in the range of 300-3000 were obtained in a 60-min extraction, and detection limits were at low to sub-microg/L level with R.S.D. values between 1.5 and 10.8%. The parameters that affected analyte enrichment were studied. This approach offers an attractive alternative to the current US Environmental Protection Agency standard methods for HAA analysis, which require complex sample preparation and derivatization prior to analysis by gas chromatography. SLMME can also be used in conjunction with other analytical schemes, such as, ion chromatography and capillary electrophoresis.     

液-液萃取衍生气相色谱法测定饮用水中卤乙酸

建立了测定饮用水中5种卤乙酸的检测方法。水样经硫酸酸化、叔丁基甲醚萃取、硫酸-甲醇衍生化后,用气相色谱电子捕获检测器测定。5种卤乙酸平均加标回收率为74.5%~104.0%,相对标准偏差为3.1%~11.0%(n=6),最低检出限为0.3~15.3μg/L。该法适用于饮用水中卤乙酸的测定。     

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.     

In‐line preconcentration capillary zone electrophoresis for the analysis of haloacetic acids in water

Two in‐line enrichment procedures (large volume sample stacking (LVSS) and field amplified sample injection (FASI)) have been evaluated for the CZE analysis of haloacetic acids (HAAs) in drinking water. For LVSS, separation on normal polarity using 20 mM acetic acid–ammonium acetate (pH 5.5) containing 20% ACN as BGE was required. For FASI, the optimum conditions were 25 s hydrodynamic injection (3.5 kPa) of a water plug followed by 25 s electrokinetic injection (?10 kV) of the sample, and 200 mM formic acid–ammonium formate buffer at pH 3.0 as BGE. For both FASI and LVSS methods, linear calibration curves (r²>0.992), limit of detection on standards prepared in Milli‐Q water (49.1–200 μg/L for LVSS and 4.2–48 μg/L for FASI), and both run‐to‐run and day‐to‐day precisions (RSD values up to 15.8% for concentration) were established. Due to the higher sensitive enhancement (up to 310‐fold) achieved with FASI‐CZE, this method was selected for the analysis of HAAs in drinking water. However, for an optimal FASI application sample salinity was removed by SPE using Oasis WAX cartridges. With SPE‐FASI‐CZE, method detection limits in the range 0.05–0.8 μg/L were obtained, with recoveries, in general, higher than 90% (around 65% for monochloroacetic and monobromoacetic acids). The applicability of the SPE‐FASI‐CZE method was evaluated by analyzing drinking tap water from Barcelona where seven HAAs were found at concentration levels between 3 and 13 μg/L.     

Optimisation and comparison of several microextraction/methylation methods for determining haloacetic acids in water using gas chromatography

This article presents the different modes and configurations of liquid-phase microextraction (LPME) through comparison with headspace solid-phase microextraction (HS-SPME) for the simultaneous extraction/methylation of the nine haloacetic acids (HAAs) found in water. This is the first analytical case reported of solvent bar extraction–preconcentration–derivatisation assisted by an ion-pairing transfer for HAAs. In this method, 5 μL of the organic extractant, decane, was confined within a hollow-fibre membrane that was placed in a stirred aqueous sample containing the derivatising reagents (dimethylsulphate with a tetrabutylammonium salt). With heating at 45 °C in the HS-SPME method, some organic solvents (extractant, excess of derivatising reagent) are also volatilised and compete with the esters on the fibre (the fibre is damaged and it can be reused only 50−60 times). In addition, the HS-SPME method provides inadequate sensitivity (limits of detections between 0.3 and 5 μg/L) to quantify HAAs at the level usually found in drinking waters. Alternative headspace LPME methods for HAAs require heating (45 °C, 25 min) to derivatise and volatilise the esters but, by using solvent bar microextraction (SBME), the extraction/methylation takes place at room temperature without degradation of HAAs to trihalomethanes. Adequate precision (relative standard deviation of approximately 8%), linearity (0.1–500 μg/L) and sensitivity (10 times higher than the HS-SPME alternative) indicate that the SBME method can be a candidate for routine determination of HAAs in tap water. Finally, the SBME method was applied for the analysis of HAAs in tap and swimming pool water and the results were compared with those of a previous validated headspace gas chromatography–mass spectrometry method.      

The Challenging Role of Chromatography in Environmental Problems

This review details the contribution of ion chromatography (IC) to environmental analysis. With reference to the problems usually encountered in environmental analysis (low concentrations to be detected and matrix interference), applications of IC in the analysis of inorganic cations in water and in the analysis of the platinum group elements (PGEs) in air particulate matter, and the advantages of this technique over more traditionally accepted analytical techniques will be discussed. Other current environmental topics, for example the occurrence of haloacetic acids (HAAs) in drinking water, will be covered, highlighting the importance of IC as an emerging powerful tool for monitoring HAAs, recognized also by the EPA that recently adopted it in a regulated method (Method 557).     

A convenient and sensitive method for haloacetic acid analysis in tap water by on‐line field‐amplified sample‐stacking CE–ESI‐MS

In this study, we propose a simple strategy based on flow injection and field‐amplified sample‐stacking CE–ESI‐MS/MS to analyze haloacetic acids (HAAs) in tap water. Tap water was passed through a desalination cartridge before field‐amplified sample‐stacking CE–ESI‐MS/MS analysis to reduce sample salinity. With this treatment, the signals of the HAAs increased 300‐ to 1400‐fold. The LODs for tap water analysis were in the range of 10 to 100 ng/L, except for the LOD of monochloroacetic acid (1 μg/L in selected‐ion monitoring mode detection). The proposed method is fast, convenient, and sensitive enough to perform on‐line analysis of five HAAs in the tap water of Taipei City. Four HAAs, including trichloroacetic acid, dichloroacetic acid, dibromoacetic acid, and monobromoacetic acid, were detected at concentrations of approximately 1.74, 1.15, 0.16, and 0.15 ppb, respectively.     

Determination of haloacetic acids in water using layered double hydroxides as a sorbent in dispersive solid‐phase extraction followed by liquid chromatography with tandem mass spectrometry

In the present study, highly efficient and simple dispersive solid‐phase extraction procedure for the determination of haloacetic acids in water samples has been established. Three different types of layered double hydroxides were synthesized and used as a sorbent in dispersive solid‐phase extraction. Due to the interesting behavior of layered double hydroxides in an acidic medium (pH?4), the analyte elution step was not needed; the layered double hydroxides are simply dissolved in acid immediately after extraction to release the analytes which are then directly introduced into a liquid chromatography with tandem mass spectrometry system for analysis. Several dispersive solid‐phase extraction parameters were optimized to increase the extraction efficiency of haloacetic acids such as temperature, extraction time and pH. Under optimum conditions, good linearity was achieved over the concentration range of 0.05–100 μg/L with detection limits in the range of 0.006–0.05 μg/L. The relative standard deviations were 0.33–3.64% (n = 6). The proposed method was applied to different water samples collected from a drinking water plant to determine the concentrations of haloacetic acids.     

Preconcentration and separation of haloacetic acids by ion chromatography

A comparative study was made of the chromatographic behaviour of five haloacetic acids (mono-, dibromoacetic and mono-, di-, trichloroacetic acids). The techniques investigated included reversed-phase ion interaction chromatography with UV detection, suppressed and non-suppressed anion-exchange chromatography. The systems are discussed studying the retention as a function of the mobile phase parameters and the stationary phases used (LiChrospher 100 RP-18, IonPac AS9, AS10 and AS11). A preconcentration step, performed on different substrates, namely LiChrolut-EN and activated vegetal carbon, has been optimized in order to reduce the method detection limits. Results obtained for drinking water samples are shown.