Method for Detecting Perchlorate in Bottled Water
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.1OImIal of the Science of Food and Agriculture J Sci Food Agric 80:1798-1804 (online: 2000) Edward T Urbans~y, 1. Baohua GU,2 Matthew L Magnuson,1 Gilbert M Brown3 and Catherine A Kelty I , Uniled States EnvIrmmen8JProt8Cfon Agency, Offlce of ReseBICh8M ~, Nstiona/Risk ManagementR-m ~, WsW Supplyand WaterR~ DIvisIon,CkJdnnatf, OH 45268, USA 2En~taI Sc/encssDMskJII, Oak Ridge N8tkJn8lL8boratOIy, Oak Ridge, TN 37831, USA* 3Chemic8and AI8Iytk:a/ ScienC8SD;visIon. Oak Ridge NationalLabOIafOIY. Oak Ridge, TN 37831, USA* Abstract: Perchlorate has been identified in ground and surface waters around the USA including some that serve as supplies for drinking water. Because perchlorate salts are used as solid oxidants in rockets and ordnance, water contamination may occur near military or aerospace installations or defense industry manufacturing facilities. This ion has been added to the Environmental Protection Agency's Contaminant Candidate List and the Unregulated Contaminant Monitoring Rule. Concern over perchlorate has prompted many residents in affected areas to switch to bottled water; however, bottled waters have not previously been examined for perchlorate contamination. Should the EPA promulgate a regulation for municipal water systems, US law requires the Food and Drug Administration to take action on bottled water. Methods will therefore be required to determine perchlorate concentrations not only in tap water, but also in bottled waters. Ion chromatography (IC) is the primary technique used for its analysis in drinking water, but it does not provide a unique identification. Confirmation by electrospray ionization mass spectrometry (ESI-MS) can serve in this capacity. The ESI-MS method can be applied to these products, but it requires an understanding of matrix effects, especially of high ionic strength that can suppress electrospray. When using methyl isobutyl ketone (MIBK) as the extraction solvent, the ESI-MS method can reach lower limits of detection of 6ngml-1 for some bottled waters. However, dilution required to negate ionic strength effects in mineral waters can raise this by a factor of 10 or more, depending on the sample. Decyltrimethylammonium cation (added as the bromide salt) is used to produce an ion pair that is extracted into MIBK. After extraction, the sum of the peak areas of the ions C1oH21NMe3(Br)(CIO4)- (mlz=380) and C1oH21NMe3(CIOJi (mlz=400) is used to quantitate perchlorate. Standard additions are used to account for most of the matrix effects. In this work, eight domestic brands and eight imported brands of bottled water were comparatively analyzed by the two techniques. For comparison, a finished potable water known to contain perchlorate was also tested. None of the bottled waters were found to contain any perchlorate within the lower limit of detection for the IC method. Recoveries on spiked samples subjected to the IC method were ~98%. Published in 2000 for SCI by John Wiley & Sons, Ltd Keywords: bottled water; perchlorate; ion chromatography; electrospray ionization mass spectrometry; drinking water INTRODUCTION surface waters at concentrations ranging from 5 ng In 1997, perchlorate ion was found in sources of ml-1 to 3.7mgml-1.1 It is believed that me per- drinking water for much of the south western USA chlorate is largely derived from defense and aerospace including the Colorado River .1-3 Improvements in ion industry practices and military operations mat took chromatography for this moiety have resulted in lower place decades ago. limits of detection on the order of 5 ngml-1 (parts per Perchlorate is a strong oxidant, and this behavior is billion) and made detection possible at these sites.2-10 obvious when hot concentrated perchloric acid Perchlorate has since been found in ground and touches organic matter. Nonemeless, perchlorate . COITespondence to: Edward T Urbansj(y, United States Environmental Protection Agency, Office of Research and Deyek)pment, National Risk Management Research Laboratory, Water Supply and Water Resources DIvIsion, Cincinnati. OH 45268, USA E-mail: [email protected] t This article is a US Government work and is in the publk: domain in the USA. * Oak Ridge National Laboratory is operated under oontract by University of T ennessee-Battelle LLC for the US Department d Energy. (R8Oeived 24 Febfuaty 2000; revised veIsiCH1received 24 April 2000; scoept8d 31 May 2000) Published in 2000 for SCI by John Wiley &: Sons, ud 1798 SunJey of boulBd waun for /)I1f:h/orQteby ESI-MS reduction is encumbered by a high activation energy, natural springs. Both brands are then purified by which precludes reaction under cold and dilute reverse osmosis. Other bottled waters, such as conditions. The chemistry of perchlorate has been Grayson Mountain Springs, Dannon, Polar Mountain reviewed previously. 1 As a consequence of this Water, Evian, San Pellegrino, Naya and Perrier are activation barrier, perchlorate is quite unreactive and taken from specific natural springs. Both Perrier and thus long-lived under the dilute and relatively cold San Pellegrino are naturally carbonated. Some inter- conditions encountered in natural bodies of water, nationally distributed bottled waters are taken from finished potable water supplies, and in biophysiology specific springs and therefore represent widespread (as when water is consumed by people or animals). In geographical exposure for North American and tenus of public health, perchlorate interferes with European nations, even if the products are consumed iodide uptake in the thyroid gland because the tWo by a relatively small fraction of the population. anions are similar in size.1,3,11,12The BPA National Consumption of this nature presents cha1Iengesfor Center for Environmental Assessmenthas undertaken risk assessmentand management. Products such as studies to determine safe levels for exposure to this Dasani and Aquafina represent a local bottler's water contaminant. Meanwhile, tWo provisional action levels source and thus a localized geographical zone of of 4 and 18ngml-1, based on different assumptions exposure. Of course, they must be tested on a local used in the original toxicology studies, remain in force. scale as they represent the specific source for a bottler At present, the BPA Office of Water has not and not for the brand overall. established a national primary drinking water standard for perchlorate; however, this ion has been added to the Contaminant Candidate List (CCL)13.14 and the Unregulated Contaminants Monitoring Rule (UCMR).15 If the BPA promulgates a drinking water EXPERIMENTALPROCEDURE regulation, the Food and Drug Administration (FDA), Sample procurement and custody will be required to act on bottled water, pursuant to 21 Bottled waters were obtained by EPA staff. Manufac- USC 349. Newspaper accounts have suggested that turer seals were broken by EPA staff in the laboratory; many people in areas with perchlorate-contaminated 1.2-dl portions were decanted into new polypropylene drinking water have switched to bottled water, or high-density polyethylene bottles, placed in sealed although bottled waters have not so far been tested packages to ensure chain of custody, and sent to the to our knowledge. Oak Ridge National Laboratory (ORNL) by overnight Previously, we reported on the determination of carrier, where they were opened exclusively by ORNL perchlorate in drinking water using electrospray staff. Perrier and San Pellegrino were allowed to ionization mass spectrometry (ESI-MS).16-19 Per- de-gas CO2 prior to use. For comparison, a perchlo- chlorate anion may be extracted into organic solvents rate-tainted potable water sample (Southern Nevada using surfactant cations, especially aikyltrimethylam- Water Authority) was also subjected to the experi- monium ions (eg decyl, lauryl, myristyl or cetyl).17-19 mental procedure. Tested waters are listed in Table 1. Other investigators also report quantitation of per- chlorate by mass spectrometric methods.20-23In this Electrospray Ionization mass spectrometric work, we examine the application of this approach as analyses well as the ion chromatographic method to ten brands Reagents of bottled water. Ion chromatography can be a useful High purity deionized water (HP DI water) was screening tool. If a sample is chromatographed and no prepared by polishing house deionized water (reverse peak is observed, a fortified sample can be tested. If osmosis/UV-irradiation) with a Barnstead EasyPure recovery of the spike is satisfactory, there is reasonable system with organic-removal and deionizing cartridges assurance that the analyte is not present. One of the to obtain a resistivity ~18MQcm. The cationic weaknessesof any chromatographic method is that surfactant, decyltrimethylammonium bromide identification by retention time is not necessarily (CI~INMe3Br), was obtained from Fluka (Buchs, unique. Confirmatory testing can be accomplished Switzerland) and prepared at O.20M (5.6gdl-l) by effectively by mass spectrometry because of the mass dissolving the solid in HP DI water. The choice of of the ion and the resulting m/z ratio. Isotopic ratios surfactant involves striking a balance among three based on relative abundance (in this case 35CI vs 37CI main factors: the ability form extractable ion pairs, with a 3:1 ratio) provide additional evidence that the availability of the reagent in high purity, and resistance identification is correct. to forming intractable emulsions, as descnoed pre- Bottled waters can vary significantly in ionic viously.IS HPLC grade 4-methyl-2-pentanone strength,