Microbial Inhibitors for U.S. EPA Drinking Water Methods for the Determination of Organic Compounds

Abstract

Preservation of chemical analytes in drinking water samples is necessary to obtain accurate information concerning contaminant occurrence. Sample preservation to prevent biodegradation is important for most samples and analytes. With the unique demands of environmental methods, it is not always possible to kill all microorganisms without having undesirable effects. To find a suitable preservative, the sample, analysis, and preservation needs should be considered. During method development of U.S. Environmental Protection Agency (EPA) Methods 526 (for unstable semivolatile compounds) and 532 (for phenylurea pesticides), a number of studies were conducted to identify compatible microbial inhibitors. Copper sulfate was successfully used in Method 532 and is an excellent firstchoice antimicrobial agent for many applications. Copper sulfate can catalyze hydrolysis reactions for some pesticides such as those analyzed in Method 526. Under these conditions, a nonmetal compound of antimicrobial activity must be considered. During the development of Method 526, a survey of alternate organic based antimicrobial compounds found that diazolidinyl urea worked well in the method. Several other candidate microbial inhibitors were identified that could have application to other environmental methods. A general approach to selecting antimicrobial compounds in future environmental methods in water matrixes is discussed.

Factors influencing the stable carbon isotopic composition of suspended and sinking organic matter in the coastal Antarctic sea ice environment

“…Ryder Bay is a coastal, seasonally sea ice-covered Southern Ocean environment in which diatoms dominate the summer assemblages, with biomass of other phytoplankton such as prymnesiophytes and cryptophytes more than an order of magnitude lower (Garibotti et al, 2005 Sea ice brine was sampled using a sack hole drilling method, with samples for the stable carbon isotopic composition of CO 2 (δ 13 C CO 2 ) and [CO 2(aq) ] taken first to minimise atmospheric contamination. Samples for δ 13 C CO 2 were taken using a 50 ml syringe and gently injected into a 12 ml glass exetainer vial preloaded with 50 µL of 35 gL −1 copper (II) sulphate to suppress bacterial activity (Winslow et al, 2001).…”

“…For δ 13 C CO 2 , water was drawn from the Niskin bottle using a 50 ml syringe and gently injected into a 12 ml glass exetainer vial preloaded with 50 µL of 35 gL −1 copper sulphate to suppress bacterial activity (Winslow et al, 2001). Samples for alkalinity and pH, for [CO 2(aq) ] determination, were taken from the Niskin straight into a 250 ml glass BOD bottle, which was immediately sealed with a ground glass stopper whilst overflowing and ensuring that no air bubbles were present.…”

Measuring Carbon-based Contaminant Mineralization Using Combined CO₂ Flux and Radiocarbon Analyses

“…Conduct initial groundwater sampling as needed to obtain initial pH, dissolved inorganic carbon (DIC) concentrations and cation concentrations 10,18 . Fill a 40 ml volatile organic analysis (VOA) vial, from the bottom to a convex meniscus with groundwater (sample via bailer, peristaltic pump, or vacuum line), add 5 drops of saturated CuSO 4 solution 19 , cap tightly (must use septum caps) with as little headspace as possible.…”

Preservation and analytical procedures for the analysis of chloro-s-triazines and their chlorodegradate products in drinking waters using direct injection liquid chromatography tandem mass spectrometry

“…Previous work by Winslow et al [24] described acceptable recoveries for cyanazine in field samples using sodium omadine (64 mg/L) to inhibit microbial activity. The dechlorination scheme was challenged with 6 mg/L of FAC, which is 50% higher than the MRDL [22].…”

“…Although the positive control pour plates indicated a vigorous microbial population (average CFU/mL per sample = 663), all other samples had virtually no growth because the ammonium acetate buffer yielded a residual chloramine that was persistent throughout the storage period (total chlorine 0.8 mg/L). The US water systems that do not rely on chlorination for disinfection would not be afforded the secondary protection of chloramines; however, the original work done by Winslow et al confirmed the antimicrobial effectiveness of sodium omadine in pour plate studies using ascorbic acid as the dechlorinating reagent [24].…”