Analysis Of Haloacetic Acids Research Articles

Optimization of a ultra-high-pressure liquid chromatography-tandem multiple reaction monitoring mass spectrometry method for monitoring haloacetic acids as chlorinated disinfection by-products in the fresh-cut industry

Haloacetic acids (HAAs) are one of the most important chlorinated disinfection by-products generated during water disinfection in the fresh-cut industry, and they can remain in the product, resulting in a consumer health risk. In this study, ultra-high-pressure liquid chromatography-tandem multiple reaction monitoring mass spectrometry (UHPLC-MRM) analysis used for drinking water was optimized and applied for the quantification of nine HAAs (HAA9) in fresh-cut lettuce and process water samples, with the complex matrix interferences for separation, and quantification problems. The method showed good selectivity, specificity and linearity, satisfactory values for trueness (recoveries of 80–116 %), precision (<22 %), and uncertainty (<55 %). Quantification limits varied from 1 to 5 µg L−1 or µg kg−1. The matrix effect for tribromoacetic, bromochloroacetic and chlorodibromoacetic acid was corrected by matrix-matched calibration and standard addition. After storage at -20 °C, only monobromoacetic acid was the HAA which loss happened after 7 days. The application of the methodology in lettuce and process water samples from the industry was successfully implemented. Therefore, this method could be employed for the quality control and regulatory analysis of HAAs in fresh products and process water from the fruit and vegetable industry.

Derivatization-free multi-step extraction for trace haloacetic acids analysis with ion chromatography: Performance and mechanisms

Haloacetic acids (HAAs) are a type of disinfection byproducts commonly found in drinking water with carcinogenic, mutagenic, or teratogenic risks to humans. Currently, the analytical methods of trace HAAs are either labor-intensive or very expensive. We herein propose a facile multiple-step extraction strategy for HAAs analysis with common ion chromatography (IC). This study is based on a fundamental water chemistry principle that HAAs become protonated featuring positive logKow values (> 0.34) under pH < pKa but deprotonated featuring negative logKow values (< −2.37) under pH > pKa. By taking advantage of the species and property switches, HAAs can be extracted and enriched into methyl tert-butyl ether first at pH < 0.5 and then back-extracted into neutral water and enriched again. Equally important, interfering anions in IC chromatogram are eliminated because they have negative logKow values. Verification results show that HAAs were enriched by 11.4 times in average while interfering anions were almost eliminated (> 99%). Although similar to USEPA Method 552.3 in method detection limits (0.033–0.246 μg/L), recoveries (70%~110%), and relative standard deviations (< 9.91%), this method took ≤ 70 min to run a batch of samples without derivatization, which takes over 2 h. The methodology may be applicable to other pollutants that also have contrasting Kow values at different pH.

A simple liquid-liquid extraction-gas chromatography-mass spectrometry method for the determination of haloacetic acids in environmental samples: Application in water with Microcystis aeruginosa cells

An analytical liquid-liquid extraction-gas chromatography–mass spectrometry (LLE-GC-MS) method was developed for the determination of nine haloacetic acids (HAAs) in water. Under the optimized conditions, the matrix-matched calibration curves of all analytes presented correlation coefficients higher than 0.99 (range level of 2–1000 μg L−1). The LODs and LOQs were <2.6 μg L−1 and <3.9 μgL−1, respectively. The relative standard deviations (RSDs) of the intra and inter-day precisions varied in the ranges of 0.01–7.31% and 1.68–19.07%, respectively. RSDs of the accuracy were 0.02–7.31%, and the recoveries were 79.71–113.22%. The validated method had a comparable LODs to similar previously reported techniques in addition to an enhanced LOQs, precision, accuracy, and recovery. Compared with reported LLE-GC-MS methods, the use of distilled H2SO4 in the methylation reaction using acidic methanol favored the process. The GC run time for HAA analysis was 25.5 min. Finally, the proposed procedure was successfully applied to the determination of low concentrations of dichloroacetic acid and trichloroacetic acid, formed during the chlorination of water in the presence of the cyanobacteria Microcystis aeruginosa.

Simultaneous analysis of 11 haloacetic acids by direct injection-liquid chromatography-electrospray ionization-triple quadrupole tandem mass spectrometry and high resolution mass spectrometry: occurrence and evolution in chlorine-treated water.

A fast, simple, selective, and sensitive method for the analysis of 11 haloacetic acids (HAAs) in chlorine-treated water has been developed. The method is based on liquid chromatography-electrospray ionization-triple quadrupole tandem mass spectrometry (LC/ESI-QqQ-MS/MS) with direct injection of the aqueous sample. The main novelty of this method over the previously published procedures based on different techniques of mass spectrometry with direct injection is the combination of the simultaneous analysis of three types of HAAs (chlorinated, brominated, and iodinated) with its simplicity and low LODs (0.01-0.6μg/L), avoiding the use of ion-pairing reagents for LC as well as the complexity and high cost of other techniques such as ion chromatography and capillary electrophoresis coupled to tandem mass spectrometry (IC-MS/MS and CE-MS/MS). The developed method was compared with another procedure carried out in our laboratory based on direct injection-liquid chromatography-electrospray ionization-high-resolution mass spectrometry with an Orbitrap analyzer (LC/ESI-Orbitrap-HRMS). The application of this technique to HAA analysis had not been previously described. LODs achieved by LC-HRMS (0.01-2μg/L) were higher than the ones obtained by LC-MS/MS. Therefore, the LC/ESI-QqQ-MS/MS method was applied to the analysis of real samples. Quality parameters were calculated with satisfactory results and real samples related to three drinking water treatment plants (DWTPs), tap water, and the drinking water distribution system of Barcelona area (Catalonia, NE Spain) were analyzed. Furthermore, the evolution of HAA concentration along time in a DWTP-treated water sample was studied.

Analysis of Haloacetic Acids (HAA5) in Waters of Public Schools and Residencies in Maring&#225;-Brazil

For water to become suitable for human consumption in most water treatment plants this occurs by making use of the chlorination process where the organic matter is destroyed by the action of chlorine. Chlorine is a disinfectant that at low concentrations meets requirements such as not being toxic to humans and inactivating microorganisms. The reaction of chlorine with organic compounds results in chlorination byproducts, many potentially harmful to human health, such as trihalomethanes, haloacetic acids, among others. The present work aimed to collect and analyze samples of treated water from reservoirs from public schools in the city of Maringá, Brazil. Analyses of haloacetic acids (HAA5: monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, bromoacetic acid and dibromoacetic acid), natural organic compounds and free residual chlorine were performed (the latter analysis, in loco). The water collection points were chosen in order to maximize the concentration of haloacetic acids that characterize network distant points from treatment station and also samples near the water treatment plant. With the results, the formation of haloacetic acids between the entrance water of the school and the water of the reservoir of the collection points were compared, where higher values were obtained in the reservoirs. Furthermore, the haloacetic acid levels of water supplied to the population close to the treatment station and distant points of the treatment station were compared, resulting in larger values at the distant points. The value of 0.170 mg/L in haloacetic acid (the maximum value allowed by the legislation is 0.080 mg/L) was obtained at a point distant in the network from the treatment plant. The Consolidation Ordinance n.5/2017, current legislation for treated water in Brazil, was used in relation to the maximum allowable values for free residual chlorine and haloacetic acids.

Electrochemical fingerprints of brominated trihaloacetic acids (HAA3) mixtures in water

In this work, we explore the capabilities of combining electrochemical sensors and chemometrics towards the analysis of haloacetic acids (HAAs) in water samples. Our approach is based on electronic tongue principles. It combines voltammetric measurements on a gold electrode with chemometric data processing, to extract characteristic fingerprints for HAAs. Cyclic and square wave voltammograms were pre-processed by means of fast Fourier transform (FFT) to provide the coefficients used as subsequent inputs for an artificial neural network (ANN) model. We were able to quantitatively detect and discriminate each HAA under study. Quantitation of HAA3 mixtures (i.e. bromodichloroacetic acid, dibromochloroacetic acid and tribromoacetic acid) was achieved at the μg/L level, with a normalized root mean square error (NRMSE) of 0.054 for the validation subset. Finally, successful analysis of spiked water samples was achieved demonstrating the operation of the sensor in the absence of matrix effects.

Analysis of haloacetic acids, bromate, and dalapon in natural waters by ion chromatography–tandem mass spectrometry

The addition of oxidants for disinfecting water can lead to the formation of potentially carcinogenic compounds referred to as disinfection byproducts (DBPs). Haloacetic acids (HAAs) are one of the most widely detected DBPs in US water utilities and some of them are regulated by the US Environmental Protection Agency (USEPA). The present study developed a method to analyze all the compounds in the USEPA method 557 (nine HAAs, bromate and dalapon) plus four potentially more toxic iodinated HAAs in water by coupling ion chromatography with tandem mass spectrometry (IC–MS/MS). This aqueous direct injection method has significant advantages over traditional GC methods, which require a derivatization and sample extraction that are laborious, time-consuming, and can negatively impact reproducibility. The method developed in this study requires half the time of the current USEPA method 557 on IC–MS/MS while including more compounds and achieving sub-μg/L level method detection limits (MDLs) for all 15 target analytes. The single laboratory lowest concentration minimum reporting level (LCMRL) has also been determined in reagent water, which ranged from 0.011 to 0.62μg/L for the analytes. The mean recoveries of the analytes during matrix spike recovery tests were 77–125% in finished drinking water and 81–112% in surface water. This method was then applied to untreated, chlorinated, and chloraminated groundwater and surface water samples. Bromate and 9 HAAs were detected at different levels in some of these samples.

A fully-automated analyzer for determining haloacetic acid concentrations in drinking water

A fully-automated, on-line, real-time analyzer has been developed for preconcentration and analysis of haloacetic acids (HAAs). Preconcentration of HAAs is achieved by sample acidification and solid phase extraction onto a hydrophobic polymeric resin using sequential injection analysis (SIA). The HAAs preconcentrate is then analyzed using post-column reaction-ion chromatography (PCR-IC), which is selective for HAAs. Systematic optimization of SIA preconcentration parameters are described followed by detailed method detection limit (MDL), accuracy, precision, and linearity studies. MDL values for the individual HAA9 species range from 0.4 to 0.9μgL−1. Side-by-side comparison studies of HAAs analysis in 14 real-world drinking water samples from Alabama, Arkansas, Kentucky, Minnesota, Missouri, Mississippi, New York, Pennsylvania and Tennessee are presented that compare the optimized SIA-PCR-IC to USEPA Method 552.3. Trace levels of HAAs detected in select samples are reported, and the bias values calculated between the two methods are typically less than 5μgL−1 for eight of the nine individual HAAs.

Pentafluorobenzyl esterification of haloacetic acids in tap water for simple and sensitive analysis by gas chromatography/mass spectrometry with negative chemical ionization

Chlorine is the most widely used disinfectant for control of waterborne diseases in drinking water treatment. It can react with natural organic matter in water and form haloacetic acids (HAAs). For analysis of HAA levels, derivatization with diazomethane is commonly recommended as the standard methodology in Japan. However, diazomethane is a carcinogenic alkylating agent. Therefore, in this study, a safe, simple, and sensitive quantification method was developed to monitor HAAs in drinking water. Pentafluorobenzyl esterification was used for pretreatment. The pentafluorobenzyl-ester derivative was detected by gas chromatography–negative ion chemical ionization-mass spectrometry analysis with very high sensitivity for HAAs analysis. The method has low detection limits (8–94ngL−1) and good recovery rates (89–99%) for HAAs. The method was applied to 30 tap water samples from 15 cities in the Kansai region of Japan. The levels of HAAs detected were in the range 0.54–7.83μgL−1. Dichloroacetic acid, trichloroacetic acid, and bromochloroacetic acid were the major HAAs detected in most of the tap water, and accounted for 29%, 20% and 19% of the total HAAs, respectively. This method could be used for routine monitoring of HAAs in drinking water without exposure of workers to occupational hazards.

In situ derivatization coupled to microextraction by packed sorbent and gas chromatography for the automated determination of haloacetic acids in chlorinated water

A novel analytical method is reported for the determination of monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, and dibromoacetic acid. These are the five haloacetic acids (HAAs) for which the U.S. Environmental Protection Agency (US EPA) has regulated a maximum contamination level (MCL) of 0.060mgL−1 for the sum of their concentrations in drinking waters. The method uses in situ aqueous derivatization, followed by microextraction by packed sorbent (MEPS) prior to gas chromatography–mass spectrometry (GC–MS). The parameters affecting derivatization and extraction were optimized with a view to obtaining maximum sensitivity. The HAAs were derivatized with 2,2,2-trifluroethylamine (TFEA), using N-ethyl-N′-(3-dimethylaminopropyl) carbodiimide (EDC) as a condensation agent. The reaction occurred in aqueous medium and was carried out in 10min in the vial of an autosampler used to perform microextraction by packed sorbent. The whole process, from the mixing of the reagents for the derivatization, was automated. Precision values varied from 4.2 to 9.8% (as intra-day relative standard deviation, RSD) and 9.4 to 14% (as inter-day RSD). The recoveries from spiked concentrations ranged from 83 to 117%, revealing the accuracy of the method. The detection limits ranged from 0.36 to 1.2μgL−1, such that it is possible to measure the US EPA MCL in drinking waters. The method developed was applied to the analysis of HAAs in drinking and swimming pool water from Salamanca (North West of Spain).

Development of dry derivatization and headspace solid-phase microextraction technique for the GC-ECD determination of haloacetic acids in tap water

A simple, fast and efficient liquid-liquid extraction (LLE) technique using headspace solid-phase microextraction (HS-SPME), in conjunction with gas chromatography-electron capture detection (GC-ECD) has been developed for the determination of haloacetic acids (HAAs) in tap water. The analytical procedure involves LLE, evaporation of extraction solvent to dryness, derivatization of HAAs into their methyl esters with acidic methanol, HS-SPME using 100-μm polydimethylsiloxane (PDMS) fiber, and GC-ECD determination. The derivatization process was optimized in dry conditions to achieve maximum sensitivity using the following conditions: esterification for 10 min at 55°C in 50 μL methanol, 30 μL sulphuric acid and 0.1 g anhydrous sodium sulphate. The HS-SPME conditions were also optimized and good sensitivity was obtained at a sampling temperature of 25°C, an absorption time of 10 min and a desorption time of 2 min. The linear calibration curves were observed for the concentration ranging from 0.1 to 200 μg/L with the correlation coefficients (R2) greater than 0.993 and the relative standard deviation (RSD) less than 12%. The method detection limits of all analytes ranging from 0.02 to 0.7 μg/L were obtained. The proposed method is compared directly to standard EPA method 552.2 in drinking water, and significant advantage in terms of selectivity was observed. Finally the optimized procedure was applied to the analysis of HAAs in Bizerte drinking water. The studied HAA were detected in all the water samples and the concentration of total HAA5 ranged from 17.8 to 70.3 μg/L.

Simultaneous formation and biodegradation of HAAs in slow sand filters: effects of residual chlorine in filter influent

Haloacetic acids (HAAs) are one of the major groups of chlorinated disinfection by-products in drinking water. This study explored the formation, speciation, and aerobic biodegradation of HAAs under different influent chlorine doses in batch reactor and simulated slow sand filtration (SSF) columns. The results showed that 90% of HAAs were biodegraded when no residual chlorine was present in SSF influents, and the bromine–HAAs were more biodegradable than chlorine–HAAs. In the batch systems, presence of 0.1 mg/L of free chlorine decreased both the heterotrophic plate counts and HAAs removal rates. The HAAs concentration increased predominantly when the chlorine concentration was higher than 0.5 mg/L. In the simulated labscale SSF columns, the 60 cm depth of SSF column provided the highest HAA percentage removal. When the influent chlorine concentration was higher than 0.5 mg/L, HAA formation was observed and particularly for the tri-haloacetic acids. The results of HAAs analysis in different bed depth showed that the middle and bottom sections of SSF also play an important role for HAA degradation.

Optimization of gas chromatographic analysis of halogenated acids in drinking water using full factorial experimental design

An analytical method based on gas chromatography–mass spectrometry (GC–MS) has been developed to determine non-volatile fraction of disinfection by-products (DBP) in drinking water. Solid phase extraction (SPE) with tri-methyl-ammonium chlorine (TMA-Cl) cartridges is followed by derivatization of desired analyte in the eluted extract. The studied factors are elution volume, methy-tertiary-butyl ether (MTBE) volume and derivatization time. Experimental design was used to investigate and subsequently used to optimize the elution volume of derivatizing agent (10% acidic methanol), MTBE volume and derivatization time for haloacetic acids (HAAs) extraction in the water sample. Regression models and desirability functions were applied to find an experimental setup for acquiring the highest global extraction yield of HAAs. The elution volume and derivatization time were the only statistically significant factors from this study. In the final optimized conditions, the procedure was applied to the SPE–GC–MS analysis of HAAs in water samples with better figures of merit. This modified method has advantage over the EPA method 552.1.

Analysis of haloacetic acids in water and air (aerosols) from indoor swimming pools using HS-SPME/GC/ECD

A solid phase microextraction method was used for the analysis of nine haloacetic acids (HAAs) in water and air (aerosols) from indoor swimming pools (ISPs). The analysis is characterized by derivatization of HAAs to their methyl-esters with dimethyl sulphate, headspace solid phase microextraction (HS-SPME) with a Carboxen–polydimethylsiloxane (CAR-PDMS) fiber and gas chromatography - electron capture detector (GC/ECD). High correlation coefficients were obtained for esters mixture calibration lines and detection limits were found to be at the low ppb level. Repeatability was assessed and coefficients of variation varied from 10 to 20%. Reproducibility was also evaluated and coefficients of variation from 15 to 25% were obtained. Analytical results from four Portuguese ISPs showed that the mean concentration of total HAAs (THAAs) in water ranged from 10 ± 2 to 183 ± 28 μg/L in which 55 ± 20% corresponded to trichloroacetic and dichloroacetic acids (TCAA and DCAA). THAAs highest concentrations were directly related to higher ISPs’ water organic matter content. In the lack of European specific regulation for water from ISPs and taking into consideration that ingestion is a form of exposure, THAAs concentration values were compared with drinking water maximum contamination level (MCL) of 60 μg/L proposed by the US EPA for the sum of five HAAs. In 35% of water sampling campaigns the sum of MBAA (monobromoacetic acid), MCAA (monochloroacetic acid), DCAA and TCAA exceeded that MCL value. The concentrations obtained for THAAs in the ISPs’ atmosphere ranged from 5 ± 1 to 64 ± 10 μg/m3 (T = 28°C at 5 cm above the water surface) and were proportional to the aerosols’ quantity, which was deeply related to indoor air ventilation system.

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 (r(2) >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.

Analysis of haloacetic acids in drinking water using post-column reaction-ion chromatography with on-line internal standardization

A post-column reaction-ion chromatography analyzer (PCR-IC) with automated internal standardization (IS) has been optimized to determine nine haloacetic acid (HAAs) species in drinking water while operating in near real-time with a one hour analysis time. The IS-PCR-IC method requires minimal sample preparation that consists of passing water samples through cartridges to remove anions and introducing the pretreated samples into the on-line channel of the automated instrumentation. Two sets of water samples have been analyzed and method detection limit (MDL), accuracy and precision measurements have been conducted prior to the water sample analysis. The experimental MDL values for the HAA species ranged from 1.4 to 7.8 μg L−1; the accuracy ranged from 75.9 to 112%; and the precision ranged from 6.2 to 34.6%. The concentration of each HAA and the Total HAAs found in these water samples were determined using internal standardization and the results were compared to USEPA Method 552.3. The bias estimates between these two methods for Total HAA9 range from −8.3 to 12.5 μg L−1.

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 muL 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 degrees 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 microg/L) to quantify HAAs at the level usually found in drinking waters. Alternative headspace LPME methods for HAAs require heating (45 degrees 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 microg/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.

Determination of Ten Haloacetic Acids in Drinking Water Using High-Performance and Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry

Haloacetic acids (HAAs) are a class of byproducts resulting from the reaction of chlorinated disinfectants with natural organic matter. These chemicals have been found in animal studies to possibly influence hepatic, reproductive, and developmental functions, and they may be mutagenic and carcinogenic. Because HAAs are hydrophilic and strongly acidic, it is a challenge to measure them at low levels. In this study, nine traditional HAAs and monoiodoacetic acid, an emerging disinfection byproduct, are analyzed in water directly. HAAs were separated on a BetaMax Acid column or a HILIC UPLC column, and they were detected by negative electrospray ionization-tandem mass spectrometry. Although the on-column limits of detection of HAAs were lower when using an HILIC UPLC column (0.08-2.73 microg/L) than when using a BetaMax Acid column (0.18 to 71.5 microg/L), to use an HILIC UPLC column, it was required to dissolve water samples in 90% acetonitrile before injection and result in sample dilution. BetaMax Acid column was found to be more suitable for the analysis of HAAs in drinking water because there was no need of sample preparation. Major species of HAAs, such as dichloroacetic acid and trichloroacetic acid, and other primary species (e.g., dibromoacetic acid, bromochloroacetic acid and bromodichloroacetic acid) can be detected using the BetaMax Acid column at concentrations higher than 1-3 microg/L.

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 (150μl–10ml) two-phase system with a tetrabutylammonium salt as phase transfer catalyst was proposed. Derivatisation with dimethylsulphate was completed in 3min 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 0.4μgl−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 10μgl−1 due to the fact that this method is less sensitive than the proposed one.

Ultrasonic enhancement of leaching and in situ derivatization of haloacetic acids in vegetable foods prior to gas chromatography–electron capture detection

A continuous ultrasound-assisted approach to enhance the extraction of nine haloacetic acids (HAAs) from vegetables with in situ derivatization to methyl esters for their gas chromatography (GC) analysis is presented. The optimization of simultaneous extraction (using acidic methanol as extractant) and derivatization enabled the completion of both steps in 15 min. Ultrasound assistance has proved to enhance both linked steps, which results in a considerable shortening of the overall analysis time ( i.e. 552.1 and 552.2 EPA methods for analysis of these compounds in drinking water require 1 and 2 h, respectively, only for derivatization). After sample preparation, the esterified HAAs were isolated by liquid–liquid extraction with n-hexane and analysed by GC–electron capture detection. The proposed method is an interesting alternative to present methods for the determination of HAAs in vegetable foods. This is an area unjustifiably forgotten by reference laboratory organisms as proved by the absence of official methods for analysis of the target compounds in these samples. The proposed method can be applied to the analysis of HAAs in any solid sample after optimization of the main variables involved in the extraction–derivatization step.