Development of U.S. EPA method 527 for the analysis of selected pesticides and flame retardants in the UCMR survey.

Method 527 was developed to address the occurrence monitoring needs of the U.S. Environmental Protection Agency (EPA) under its second unregulated contaminant monitoring rule (UCMR 2). This method includes a wide range of semivolatile organic contaminants, including pesticides that were deferred during the first UCMR, flame retardants, and pyrethroid pesticides. This paper discusses the rationale for selection and inclusion of the various contaminants included in Method 527 and describes the challenges associated with developing analytical methods that will be used for the occurrence monitoring of such a diverse group of organic molecules. Method 527 employs solid-phase extraction with analysis by gas chromatography/ mass spectrometry (GC/MS). The final method preservation scheme requires the storage of samples in amber bottles buffered at pH 3.8 using citric acid to prevent degradation from acid-catalyzed hydrolysis and from UV light. Citric acid is also an effective antimicrobial reagent, preventing this mode of loss during storage. Ethylenediaminetetraacetic acid (EDTA) is added to remove transition metals such as copper, which was determined to degrade target analytes upon storage. Finally, free available chlorine (FAC), which is present in many finished waters and found to degrade a number of the targets, is removed using ascorbic acid. The final method meets all of the EPA UCMR survey requirements for sample storage, precision, accuracy, and sensitivity and will be proposed for use under the UCMR 2.

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.

Validating sample preservation techniques and holding times for the approved compliance monitoring methods for haloacetic acids under the US EPA's stage 1 D/DBP rule.

Haloacetic acids (HAAs), which are formed during the disinfection of drinking waters with chlorine, are regulated by the US Environmental Protection Agency (EPA) under the Stage 1 Disinfectant/Disinfection Byproducts (D/DBP) Rule. Recently, three studies have been reported indicating that low concentrations of HAAs can also be formed during disinfection with chloramines. Methods currently approved for compliance monitoring under the Stage 1 Rule arrest the chlorine-mediated formation of HAAs by adding ammonium chloride, which forms chloramines. Studies were undertaken using an in-process water that favored the formation of HAAs with moderate total organic carbon concentration and high levels of chlorine to investigate the potential formation of HAAs under sample storage conditions. The ammonium chloride-quenched sample did form a small amount of HAAs, but total formation over a period equal to the 14-day sample storage time was less than 2 microg/l, whereas the unquenched samples increased 41 microg/l during the same period. Pour plate studies indicated that chlorinated drinking waters quenched with ammonium chloride are protected from microbial growth, which is an important additional advantage to this preservation scheme. The presence of a combined chlorine residual should prevent microbial degradation of HAAs in samples. These studies support the preservation protocols and the sample storage times promulgated for compliance monitoring under the Stage 1 D/DBP Rule.