Eliminating the chlorite interference in US Environmental Protection Agency Method 317.0 permits analysis of trace bromate levels in all drinking water matrices

A post-column reagent (PCR) method for bromate analysis in drinking water with a method detection limit (MDL) and method reporting limit (MRL) of 0.1 and 0.5 microg/l, respectively, has been developed by the United States Environmental Protection Agency (EPA) for future publication as EPA Method 317.0. The PCR method provides comparable results to the EPA's Selective Anion Concentration (SAC) method used to support the laboratory analysis of Information Collection Rule (ICR) low-level bromate samples and offers a simple, rugged, direct injection method with potential to be utilized as a compliance monitoring technique for all inorganic Disinfectants/Disinfection By-Products (D/DBPs). It has superior sensitivity for bromate compared to EPA Method 300.1, which was promulgated as the compliance monitoring method for bromate under Stage 1 of the D/DBP rule. This paper addresses elimination of the chlorite interference that was previously reported in finished waters from public water systems (PWSs) that employ chlorine dioxide as the disinfectant. An evaluation of Method 317.0 for the analysis of bromate in commercial bottled waters is also reported.     

Collaborative study of EPA Method 317.0 for the determination of inorganic oxyhalide disinfection by-products in drinking water using ion chromatography with the addition of a postcolumn reagent for trace bromate analysis

The development of the U.S. Environmental Protection Agency (EPA) Method 317.0 is initiated to provide a sufficiently sensitive and fundamental technique for the compliance monitoring of trace levels of bromate in drinking water. After a comparative evaluation of Method 317.0 and elimination of a chlorite interference, this method is tested by a collaborative study in order to determine the precision and bias of the method and evaluate its potential role as a future compliance-monitoring method for inorganic disinfection by-products (DBPs) and trace bromate. This technique provides a practical method for future compliance monitoring for all of the inorganic oxyhalide DBPs including trace concentrations of bromate.     

Review of the methods of the US Environmental Protection Agency for bromate determination and validation of Method 317.0 for disinfection by-product anions and low-level bromate

In recent years several methods have been published by the United States Environmental Protection Agency (EPA) which specify bromate as a target analyte. The first of these was EPA Method 300.0. As technological improvements in ion chromatographic hardware have evolved and new detection techniques have been designed, method detection limits for bromate have been reduced and additional procedures have been written, including EPA Method 300.1, 321.8 and, most recently, EPA Method 317.0. An overview of the evolution of these bromate methods since 1989 is presented. The focus is specific to each of these respective procedures, highlighting method strengths, weaknesses, and addressing how these methods fit into EPA’s regulatory agenda. In addition, performance data are presented detailing the joint EPA/American Society for Testing and Materials multilaboratory validation of EPA Method 317.0 for disinfection by-product anions and low-level bromate.     

Analysis of 500-ng/l levels of bromate in drinking water by direct-injection suppressed ion chromatography coupled with a single, pneumatically delivered post-column reagent

In July 1997, the US Environmental Protection Agency (EPA) began sampling and analyzing drinking water matrices from US municipalities serving populations greater than 100 000 for low-level bromate (>0.20 μg/l) in support of the Information Collection Rule (ICR) using the selective anion concentration (SAC) method. In September 1997, EPA published Method 300.1 which lowered the Method 300.0 bromate method detection limit (MDL) from 20.0 to 1.4 μg/l. This paper describes the research conducted at the EPA’s Technical Support Center laboratory investigating a single post-column reagent, o-dianisidine (ODA), which has been successfully coupled to EPA Method 300.1 to extend the MDL for bromate. Initial studies indicate that this method offers a MDL which approaches the EPA’s SAC method with the added benefit of increased specificity, shortened analysis time and reduced sample preparation. The method provides excellent ruggedness and acceptable precision and accuracy with a bromate MDL in reagent water of 0.1 μg/l, and a method reporting limit of 0.50 μg/l.     

Challenges encountered in extending the sensitivity of US Environmental Protection Agency Method 314.0 for perchlorate in drinking water

Concerns about the potential adverse health effects of perchlorate at concentrations below the minimum reporting level (MRL) of US Environmental Protection Agency (EPA) Method 314.0 (generally recognized as 4.0 microg/l) have led to an interest in increasing the sensitivity of the method. This work describes the use of 2 mm columns with a large-loop direct injection method, a column concentration technique and this concentration technique with a background reduction step, to increase the sensitivity for the analysis of trace levels of perchlorate in high ionic strength matrices. The concentrator columns studied were the Dionex TAC LP-1 and a new Dionex high capacity Cryptand concentrator column. The use of a surrogate to monitor trapping efficiency for the concentration technique and the use of confirmational columns to minimize the potential for false positives are also discussed. The large-loop direct injection method and the column concentration methods provided acceptable data when the samples were pre-treated with solid phase pretreatment cartridges. The background reduction technique did not provide acceptable data with either of the concentrator columns evaluated.     

Characterization of the interactions in polymer-filler systems by inverse gas chromatography

Chromium is a primary drinking water contaminant in the USA with hexavalent chromium, Cr(VI), being the most toxic form of the metal. As a required step in developing a revised state drinking water standard for chromium, the California Department of Health Services recently issued a new Public Health Goal (PHG) of 2.5 microg/l for total chromium and 0.2 microg/l for Cr(VI). Hexavalent chromium can be determined (as chromate) by ion chromatography, as described in US Evironmental Protection Agency Method 218.6; however, the method as originally published does not allow sufficient sensitivity for analysis at the California PHG level of 0.2 microg/l. Modification of the conditions described in Method 218.6, including the use of a lower eluent flow-rate, larger reaction coil, and larger injection volume, significantly increases the method sensitivity. The modified method, which uses IonPac NG1 and AS7 guard and analytical columns, an eluent of 250 mM ammonium sulfate-100 mM ammonium hydroxide operated at 1.0 ml/min, a 1000 microl injection volume, and postcolumn reaction with 2 mM diphenylcarbazide-10% methanol-0.5 M sulfuric acid (using a 750 microl reaction coil) followed by UV-Vis detection at 530 nm, permits a method detection limit for chromate of 0.02 microg/l. This results in a quantitation limit of 0.06 microg/l, which is more than sufficient for analysis at the California PHG level. Calibration is linear over the range of 0.1-10 microg/l and quantitative recoveries (>80%) are obtained for chromate spiked at 0.2 microg/l in drinking water. The modified method provides acceptable performance, in terms of chromate peak shape and recovery, in the presence of up to 1000 mg/l chloride or 2000 mg/l sulfate.     

Liquid chromatographic analysis of glucosamine in commercial dietary supplements using indirect fluorescence detection

A method of using indirect fluorescence detection is evaluated for the analysis of glucosamine in commercial dietary supplements following chromatographic separation. In this method, the eluting analyte, glucosamine, was detected by monitoring an increase in the fluorescence signal for L-tryptophan (L-Trp) or DL-5-methoxytryptophan (5-MTP) after glucosamine complexed with a copper(II) ion and released either L-Trp or 5-MTP from a copper(II) complex, which is introduced postcolumn. The fluorescence of L-Trp and 5-MTP are quenched when complexed with the copper(II) ion. The results obtained using indirect fluorescence detection are compared with the results obtained for precolumn derivatization with phenylisothiocyanate. Statistical analysis is performed to compare the results obtained for the two postcolumn interaction components, Cu(L-Trp)2 and Cu(5-MTP)2, as well as the results obtained using the indirect fluorescence detection method and a precolumn derivatization method. The indirect fluorescence detection method provided an alternative to precolumn derivatization for determining the concentration of glucosamine in commercial dietary supplements. The stability of the glucosamine-o-phthalaldehyde-3-mercaptopropionic acid derivative is also evaluated to investigate the applicability of the popular precolumn derivatization reagent, o-phthalaldehyde-3-mercaptopropionic acid, for this analysis.     

Optimizing the determination of haloacetic acids in drinking waters

Three methods are currently approved by the US Environmental Protection Agency for the compliance monitoring of haloacetic acids in drinking waters. Each derivatizes the acids to their corresponding esters using either acidic methanol or diazomethane. This study was undertaken to characterize the extent of methylation of these analytes by these methods, and to fully optimize methylation chemistries to improve analytical sensitivity, precision and accuracy. The approved methods were shown to have little to no esterification efficiencies for the brominated trihaloacetic acids (HAA3). Methylation with acidic methanol was determined to be more efficient and rugged than methylation with diazomethane. A new higher boiling solvent, tertiary-amyl methyl ether, is reported which has significantly improved methylation efficiencies for HAA3. Additional modifications to the method have been made that improve method ruggedness. The revised method, EPA Method 552.3, outperforms the currently approved methods, especially for HAA3.     

Ligand-sensitized fluorescence of Tb3+ in Tb3+-dibutylphosphate complexes: application for the estimation of DBP

The fluorescence of Tb(3+) is sensitized by complexation with dibutylphosphate (DBP) and tri-n-butylphosphate (TBP). The excitation maximum for the Tb(3+)-DBP complex occurs at 218.5 nm, while that for the Tb(3+)-TBP complex is observed at 228.0 nm. Both complexes yield Tb(3+) fluorescence at 548 nm. The difference in the excitation maxima for the two complexes has been used to advantage for the estimation of DBP in the presence of TBP. DBP is the main degradation product of TBP in the PUREX process and the method described in this work can thus serve as a useful analytical tool in monitoring the quality of the TBP in the process. This method has been shown to be applicable for the estimation of DBP when present to an extent of 0.1-10% of TBP, in TBP/dodecane solutions.     

Selective method for the analysis of perchlorate in drinking waters at nanogram per liter levels, using two-dimensional ion chromatography with suppressed conductivity detection

The United States Environmental Protection Agency (EPA) collected drinking water occurrence data for perchlorate in the Unregulated Contaminant Monitoring Regulation (UCMR 1; 2001-2005) using EPA Method 314.0. To address the interest in increasing sensitivity and selectivity for the analysis of perchlorate, three new methods, EPA Methods 314.1, 331.0 and 332.0, were subsequently published by EPA for the analysis of perchlorate in drinking water. In 2006, an automated two-dimensional ion chromatography (2D-IC) method for measuring perchlorate with suppressed conductivity detection was developed. Two-dimensional IC is essentially an automated "heart-cutting", column concentration and matrix elimination technique. In the first dimension, a large sample volume is injected onto a first separation column and the separated matrix ions are diverted to waste while the analyte(s) of interest are selectively cut, trapped and concentrated in a concentrator column. In the second dimension, the contents from the concentrator column are eluted onto a second analytical column for separation and quantitation of the analyte(s) of interest. Incorporation of two columns with different affinities for the analyte(s) in a single analysis can provide comparable selectivity and superior sensitivity to a method using second column confirmation in a second separate analysis step. Use of this approach led to the development of a new, highly sensitive and selective 2D-IC, suppressed conductivity method with a Lowest Concentration Minimum Reporting Level (LCMRL) of 55 ng/L for perchlorate in drinking water samples. This new method has comparable sensitivity and selectivity and is simpler and more economical than IC-mass spectrometric (MS) or IC-MS-MS techniques. The method is now being prepared for publication as EPA Method 314.2.     

Refinement of AOAC Official Method 2005.06 liquid chromatography-fluorescence detection method to improve performance characteristics for the determination of paralytic shellfish toxins in king and queen scallops

AOAC Official Method 2005.06 LC-fluorescence detection (FLD) method is an official alternative to the mouse bioassay for the determination of paralytic shellfish poisoning (PSP) toxins in bivalve shellfish. To validate the method for species of relevance to the UK official control monitoring program, the method performance characteristics were tested for whole king and queen scallops. Validation showed that, while the performance was generally acceptable for the quantitation of non-N-hydroxylated toxins, poor toxin recovery and sensitivity was evident for the analysis of N-hydroxylated toxins following periodate oxidation. These effects occurred in a range of scallop samples with variable temporal and spatial sources. The effects were also noted in other laboratories following a small interlaboratory study. As a result, the method was refined to improve the recovery and sensitivity of analysis following the periodate oxidation step in the PSP method for scallops. Performance improved through alterations to the preparation of the periodate oxidant, use of higher volumes for C18 cleanup, and injection volumes in combination with the use of a king scallop matrix modifier for oxidation of N-hydroxylated toxin calibration standards. A single-laboratory validation of the refined method showed that the selectivity, linearity, sensitivity, recovery, and precision were acceptable and similar to values reported previously for AOAC Official Method 2005.06 in other bivalve species. Results showed the method to be rugged for all parameters investigated, including small changes to the composition of the new periodate reagent utilized in the refined method. The refined scallops LC method was subsequently compared with the European reference method. PSP-positive scallops showed an excellent agreement between the methods for queen and Atlantic scallops, with a small level of positive bias in the LC results for whole king scallops. These differences were related solely to the use of the highest toxicity equivalence factors for toxin epimeric pairs, with gonyautoxin (GTX)1,4 and GTX2,3 in particular present at high concentrations in the king scallops. Overall, the refined LC-FLD method improved the performance characteristics of AOAC Official Method 2005.06 for the determination of PSP toxins in whole king and queen scallops, and showed a good overall agreement between the official methodologies. It is, therefore, recommended as a more appropriate option for the routine monitoring of PSP toxins in these species.     

US Environmental Protection Agency Method 314.1, an automated sample preconcentration/matrix elimination suppressed conductivity method for the analysis of trace levels (0.50 microg/L) of perchlorate in drinking water

Since 1997 there has been increasing interest in the development of analytical methods for the analysis of perchlorate. The US Environmental Protection Agency (EPA) Method 314.0, which was used during the first Unregulated Contaminant Monitoring Regulation (UCMR) cycle, supports a method reporting limit (MRL) of 4.0 microg/L. The non-selective nature of conductivity detection, combined with very high ionic strength matrices, can create conditions that make the determination of perchlorate difficult. The objective of this work was to develop an automated, suppressed conductivity method with improved sensitivity for use in the second UCMR cycle. The new method, EPA Method 314.1, uses a 35 mm x 4 mm cryptand concentrator column in the sample loop position to concentrate perchlorate from a 2 mL sample volume, which is subsequently rinsed with 10 mM NaOH to remove interfering anions. The cryptand concentrator column is combined with a primary AS16 analytical column and a confirmation AS20 analytical column. Unique characteristics of the cryptand column allow perchlorate to be desorbed from the cryptand trap and refocused on the head of the guard column for subsequent separation and analysis. EPA Method 314.1 has a perchlorate lowest concentration minimum reporting level (LCMRL) of 0.13 microg/L in both drinking water and laboratory synthetic sample matrices (LSSM) containing up to 1,000 microg/L each of chloride, bicarbonate and sulfate.     

Headspace single-drop microextraction for the analysis of chlorobenzenes in water samples

Exposing a microlitre organic solvent drop to the headspace of an aqueous sample contaminated with ten chlorobenzene compounds proved to be an excellent preconcentration method for headspace analysis by gas chromatography-mass spectrometry (GC-MS). The proposed headspace single-drop microextraction (SDME) method was initially optimised and the optimum experimental conditions found were: 2.5 microl toluene microdrop exposed for 5 min to the headspace of a 10 ml aqueous sample containing 30% (w/v) NaCl placed in 15 ml vial and stirred at 1000 rpm. The calculated calibration curves gave a high level of linearity for all target analytes with correlation coefficients ranging between 0.9901 and 0.9971, except for hexachlorobenzene where the correlation coefficient was found to be 0.9886. The repeatability of the proposed method, expressed as relative standard deviation varied between 2.1 and 13.2% (n = 5). The limits of detection ranged between 0.003 and 0.031 microg/l using GC-MS with selective ion monitoring. Analysis of spiked tap and well water samples revealed that matrix had little effect on extraction. A comparative study was performed between the proposed method, headspace solid-phase microextraction (SPME), solid-phase extraction (SPE) and EPA method 8121. Overall, headspace SDME proved to be a rapid, simple and sensitive technique for the analysis of chlorobenzenes in water samples, representing an excellent alternative to traditional and other, recently introduced, methods.     

Indirect fluorescence detection of amino sugars with the use of copper complexes of tryptophan and its analogues following high-performance liquid chromatographic separation

A simple, indirect fluorescence detection method has been developed for detecting specific mono-amino sugars (D-glucosamine, D-galactosamine, D-mannosamine) following chromatographic separation. The eluting amino sugars release L-tryptophan (L-Trp) from a copper-tryptophan complex which is introduced postcolumn. Analyte detection is based on measuring the increase in L-Trp fluorescence, which is quenched when complexed with copper. Two tryptophan analogues, 5-hydroxy-L-tryptophan (5-HTP) and DL-5-methoxytryptophan (5-MTP), were also evaluated as postcolumn reagents. 5-MTP was found to be a suitable alternative to L-Trp for the detection of these mono-amino sugars. Detection limits for D-glucosamine, D-galactosamine, and D-mannosamine are in the range of 0.15-0.30 nmol injected.     

Determination of trace concentrations of bromate in municipal and bottled drinking waters using a hydroxide-selective column with ion chromatography

The International Agency for Research on Cancer determined that bromate is a potential human carcinogen, even at low micro/l levels in drinking water. Bromate is commonly produced from the ozonation of source water containing naturally occurring bromide. Traditionally, trace concentrations of bromate and other oxyhalides in environmental waters have been determined by anion exchange chromatography with an IonPac AS9-HC column using a carbonate eluent and suppressed conductivity detection, as described in EPA Method 300.1 B. However, a hydroxide eluent has lower suppressed background conductivity and lower noise compared to a carbonate eluent and this can reduce the detection limit and practical quantitation limit for bromate. In this paper, we examine the effect of using an electrolytically generated hydroxide eluent combined with a novel hydroxide-selective anion exchange column for the determination of disinfection byproduct anions and bromide in municipal and bottled drinking water samples. EPA Methods 300.1 B and 317.0 were used as test criteria to evaluate the new anion exchange column. The combination of a hydroxide eluent with a high capacity hydroxide-selective column allowed sub-microg/l detection limits for chlorite, bromate, chlorate, and bromide with a practical quantitation limit of 1 microg/l bromate using suppressed conductivity detection and 0.5 microg/l using postcolumn addition of o-dianisidine followed by visible detection. The linearity, method detection limits, robustness, and accuracy of the methods for spiked municipal and bottled water samples will be discussed.     

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).     

On-line purge and trap gas chromatography for monitoring of trihalomethanes in drinking water distribution systems

A method using an automated on-line purge and trap gas chromatograph with a dry electrolytic conductivity detector (DELCD) has been developed for monitoring four regulated trihalomethanes in drinking water distribution systems. This analyzer samples trihalomethanes from drinking water by pervaporation through a silicone capillary membrane contained within a gas extraction cell (GEC) followed by preconcentration using an adsorbent trap. Trihalomethanes are subsequently desorbed from the trap onto a capillary column, separated and detected. The analyzer operates in real-time, samples directly from the drinking water distribution system and is fully automated. The optimization, operation, and evaluation of the analyzer and method are discussed. Method detection limits (MDL) are less than 1.0 μg L⁻¹ with acceptable estimates for accuracy, and precision. The results from two on-line monitoring studies in chlorinated and chloraminated distribution systems are presented. The performance of the method is compared directly to United Stated Environmental Protection Agency Method 502.2 and shows a very slight, but acceptable bias.     

Optimization of operating conditions for the determination of perchlorate in biological samples using preconcentration/preelution ion chromatography

Perchlorate originates as a contaminant in the environment from the use of salts in the manufacture of solid rocket fuels and munitions. Monitoring potential perchlorate contamination in the environment is of interest, however, very few analytical methods have been developed for perchlorate determination in biological samples. Analysis of complex samples by ion chromatography is complicated by matrix components that can interfere with perchlorate determination. However, a recently developed preconcentration/preelution (PC/PE) ion chromatography method has demonstrated the capability to analyze certain complex samples such as high salinity water, milk, and hydroponic fertilizers. The ability of this method to reduce sample background and lower detection limits in ion chromatography for various biological samples was evaluated in this study. The PC/PE method was applicable to the analysis of kidneys, livers, zebrafish, quail eggs, lettuce, and urine. Optimal operating conditions were determined for each matrix. Ranges of optimal wash volumes were shorter when 15 mM NaOH prewash solutions were used compared with 10mM and good recovery was achieved for most matrices with an injection period > or =60s. Prewash solution concentration did not appear to significantly affect matrix background. The PC/PE method was capable of reducing sample background when compared to EPA Method 314.0, which resulted in detection limits, with the exception of zebrafish and urine, that were two-fold lower than those achieved with EPA Method 314.0.