Journal of the Science of Food and Agriculture
3 Sci Food Agric 80:1798-1804 (online: 2000)
Survey of bottled waters for perchlorate by
electrospray ionization mass spectrometry
(ESI-MS) and ion chromatography (IC)f
Edward T Urbansky,1* Baohua Gu,2 Matthew L Magnuson,1 Gilbert M Brown3 and
Catherine A Kelty1
1 United States Environrnental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory,
Water Supply and Water Resources Division, Cincinnati, OH 45268, USA
2Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA*
^Chemical and Analytical Sciences Division, Oak Ridge National Laboratory, 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 hi 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 (1C)
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 C10H21NMej(Br)(ClO,,)~
(m/s=380) and C^HjjNMe^ClO,^ (mfe=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 1C method. Recoveries on
spiked samples subjected to the 1C 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
In 1997, perchlorate ion was found in sources of
drinking water for much of the south western USA
including the Colorado River.1"3 Improvements in ion
chromatography for this moiety have resulted in lower
limits of detection on the order of Sngml"1 (parts per
billion) and made detection possible at these sites.2"10
Perchlorate has since been found in ground and
surface waters at concentrations ranging from 5ng
ml"1 to S.Tmgml"1.1 It is believed that the per-
chlorate is largely derived from defense and aerospace
industry practices and military operations that took
place decades ago.
Perchlorate is a strong oxidant, and this behavior is
obvious when hot concentrated perchloric acid
touches organic matter. Nonetheless, perchlorate
* Correspondence to: Edward T Urbansky, United States Environmental Protection Agency, Office of Research and Development, National
Risk Management Research Laboratory, Water Supply and Water Resources Division, Cincinnati, OH 45268, USA
E-mail: Urbansky.Edward@EPA.gov
f This article is a US Government work and is in the public domain in the USA.
* Oak Ridge National Laboratory is operated under contract by University of Tennessee-Battelle LLC for the US Department of Energy.
(Received 24 February 2000; revised version received 24 April 2000; accepted 31 May 2000)
Published in 2000 for SCI by John Wiley & Sons, Ltd
1798
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Survey of bottled waters for perchlorate by JSSI-JMS
reduction is encumbered by a high activation energy,
which precludes reaction under cold and dilute
conditions. The chemistry of perchlorate has been
reviewed previously.1 As a consequence of this
activation barrier, perchlorate is quite unreactive and
thus long-lived under the dilute and relatively cold
conditions encountered in natural bodies of water,
finished potable water supplies, and in biophysiology
(as when water is consumed by people or animals). In
terms of public health, perchlorate interferes with
iodide uptake in the thyroid gland because the two
anions are similar in size.1'3'11'12 The EPA National
Center for Environmental Assessment has undertaken
studies to determine safe levels for exposure to this
contaminant. Meanwhile, two provisional action levels
of 4 and ISngml"1, based on different assumptions
used in the original toxicology studies, remain in force.
At present, the EPA Office of Water has not
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 EPA promulgates a drinking water
regulation, the Food and Drug Administration (FDA),
will be required to act on bottled water, pursuant to 21
USC 349. Newspaper accounts have suggested that
many people in areas with perchlorate-contaminated
drinking water have switched to bottled water,
although bottled waters have not so far been tested
to our knowledge.
Previously, we reported on the determination of
perchlorate in drinking water using electrospray
ionization mass spectrometry (ESI-MS).16"19 Per-
chlorate anion may be extracted into organic solvents
using surfactant cations, especially alkyltrimethylam-
monium ions (eg decyl, lauryl, myristyl or cetyl).17~19
Other investigators also report quantitation of per-
chlorate by mass spectrometric methods.20"23 In this
work, we examine the application of this approach as
well as the ion chromatographic method to ten brands
of bottled water. Ion chromatography can be a useful
screening tool. If a sample is chromatographed and no
peak is observed, a fortified sample can be tested. If
recovery of the spike is satisfactory, there is reasonable
assurance that the analyte is not present. One of the
weaknesses of any chromatographic method is that
identification by retention time is not necessarily
unique. Confirmatory testing can be accomplished
effectively by mass spectrometry because of the mass
of the ion and the resulting mlz ratio. Isotopic ratios
based on relative abundance (in this case 35C1 vs 37C1
with a 3:1 ratio) provide additional evidence that the
identification is correct.
Bottled waters can vary significantly in ionic
strength, salt composition and dissolved gas content
(mainly carbon dioxide). Like municipal potable water
supplies, bottled waters vary in treatment techniques,
including disinfection. Some bottled waters, such as
Pepsi's Aquafina or Coca-Cola's Dasani are derived
from local sources — either municipal tap water or
natural springs. * Both brands are then purified by
reverse osmosis. Other bottled waters, such as
Grayson Mountain Springs, Dannon, Polar Mountain
Water, Evian, San Pellegrino, Naya and Perrier are
taken from specific natural springs. Both Perrier and
San Pellegrino are naturally carbonated. Some inter-
nationally distributed bottled waters are taken from
specific springs and therefore represent widespread
geographical exposure for North American and
European nations, even if the products are consumed
by a relatively small fraction of the population.
Consumption of this nature presents challenges for
risk assessment and management. Products such as
Dasani and Aquafina represent a local bottler's water
source and thus a localized geographical zone of
exposure. Of course, they must be tested on a local
scale as they represent the specific source for a bottler
and not for the brand overall.
EXPERIMENTAL PROCEDURE
Sample procurement and custody
Bottled waters were obtained by EPA staff. Manufac-
turer seals were broken by EPA staff in the laboratory;
1.2-dl portions were decanted into new polypropylene
or high-density polyethylene bottles, placed in sealed
packages to ensure chain of custody, and sent to the
Oak Ridge National Laboratory (ORNL) by overnight
carrier, where they were opened exclusively by ORNL
staff. Perrier and San Pellegrino were allowed to
de-gas CO2 prior to use. For comparison, a perchlo-
rate-tainted potable water sample (Southern Nevada
Water Authority) was also subjected to the experi-
mental procedure. Tested waters are listed in Table 1.
Electrospray ionization mass spectrometric
analyses
Reagents
High purity deionized water (HP DI water) was
prepared by polishing house deionized water (reverse
osmosis/UV-irradiation) with a Barnstead EasyPure
system with organic-removal and deionizing cartridges
to obtain a resistivity >18MJicm. The cationic
surfactant, decyltrimethylammonium bromide
(C10H21NMe3Br), was obtained from Fluka (Buchs,
Switzerland) and prepared at 0.20M (5.6gdr:) by
dissolving the solid in HP DI water. The choice of
surfactant involves striking a balance among three
main factors: the ability form extractable ion pairs,
availability of the reagent in high purity, and resistance
to forming intractable emulsions, as described pre-
viously.18 HPLC grade 4-methyl-2-pentanone
(methyl isobutyl ketone, MIBK) was obtained from
Spectrum Quality Chemicals (San Rafael, CA, USA)
and used as the extraction solvent. Ammonium
perchlorate (Aldrich, Milwaukee, WI, USA) was
prepared at l.OOgT1 ClO^" in HP DI water and
serially diluted as necessary.
JSdFoodAgric 80:1798-1804 (online: 2000)
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ET Urbansky et al
Table 1. Waters examined in this study
Brand
Company, address
Source
Apollinaris Naturally Sparkling Spring Water Liberty Richter (distributor), Saddle Brook, NJ 07663, USA Germany
Aquafina
Crystal Geyser Natural Spring Water
Dannon
Dasani
Eureka Springs All Natural Spring Water
Evian
Fountainhead Natural Spring Water
Gerolsteiner Natural Mineral Water
Grayson Mountains
Naya
S Pellegrino
Perrier
Poland Spring Natural Spring Water
Polar Mountain Spring Water
Southern Nevada3 Water Authority
Volvic Natural Spring Water
PepsiCo bottler was Warrenton Products Inc, Warrenton, Varies by location
MO 63383, USA
CG Roxane LP, P O Box 249, Benton, TN 37307, USA CG Roxane
Dannon National Spring Water, 208 Harbor Drive, Stamford, Spring Piedmont,
Quebec, Canada
Varies by location
Municipal tap
Cachet Spring
CT 06902, USA
The Coca-Cola Co, Atlanta, GA, USA
Saegertown Beverages, Saegertown, PA 16433, USA
SA Evian Co, Evian-Les-Bains, France
Fountainhead, White Water Falls Rd, Oconee, SC, USA
Gerolsteiner Brunnen GmbH & Co,
D-54567 Gerolstein/Vulkaneifel, Germany
Grayson Mountain Water Co, Independence, VA, USA
Nora Beverages Inc, Mirabel, Quebec, JOV1ZO, Canada
San Pellegrino, Italy
Perrier, Vergeze, France
Poland Spring Water Co, Poland, ME 04274, USA
Crystal Springs Water Co, Mableton, GA 30059, USA
Las Vegas, NV, USA
Danone Group, Ste Volvic, at Volvic 63530, France
Sumter Natural Forest
Gerolstein spring
(near Rhine, Moselle)
Local spring
Local spring
Local spring
Local spring
Local spring
Crystal Spring,
Blue Ridge, GA
Lake Mead on
Colorado River
Clairvic Spring
a SNWA is a finished potable water from a municipal plant and not a bottled water. It is used for comparison as it is known to contain perchlorate ion.
Extraction
The following were quantitatively added to a 100-ml
volumetric flask: 96.0ml of the test water sample,
1.0ml of 0.20M C10H21NMe3Br (aquesus), and 5.0ml
of MIBK. The rationale for this procedure is fairly
straightforward. The presence of small water droplets
cannot be tolerated in the ESI-MS analysis. A
separately funnel will not work because MIBK is less
dense than water (coming out second); thus, residual
water droplets left on the funnel will be carried along in
the MIBK layer. Because of the large volume of water
to MIBK, a 40-ml vial, such as that used for many
EPA drinking water methods also will not work. The
advantage to a 100-ml volumetric flask is that the
solvent is constrained to the neck, where it is readily
drawn off once the extraction is complete. We
emphasize that the flask is not used in its volumetric
capacity, but merely as a convenient vessel for
recovering the extraction solvent. Duplicate samples
were run with the following fortifications (spikes): 0
(unspiked), 10, or 20ngml~1 ClO^". As a blank,
unspiked samples of the bottled waters were extracted
without the surfactant. The blank correction proce-
dure has been explained previously.18'19 Due to
limited sample volume of the first lot, Perrier and S
Pellegrino were not run in duplicate; however, another
lot was tested in duplicate.
Instrumentation
A Finnigan-Mat (San Rafael, CA, USA) TSQ 700
quadrupole mass spectrometer (Q3) with a Finnegan-
Mat electrospray interface apparatus was used for
analysis. A Waters (Milford, MA, USA) MS-600
pump delivered pesticide residue analysis grade
methanol (Burdick & Jackson, Baxter Healthcare,
Muskegon, MI, USA) as the carrier; sheathing gas
pressure was 480 kPa (70 psi); capillary temperature
was 200°C; spray potential was 4.0kV.
Ion chromatographic analyses
Samples were analyzed at ORNL as received from
EPA following the method reported by Jackson et al. 8
Dionex (Sunnyvale, CA, USA) AG11 guard and ASH
analytical columns were used on a Dionex DX-500 ion
chromatograph for these analyses. In addition to the
test water samples, spiked samples containing 10 and
20ngml~1 CIO 7 were run to verify performance.
RESULTS AND DISCUSSION
ESI-MS data analysis
To correct for other species that form ions with mlz
equal to that of the analyte ions, the peak areas
obtained for an MIBK extract without detergent were
subtracted from those extracted with the cationic
surfactant. Perchlorate forms complexes with the
surfactant cation of the form C10H21NMe3(Br)
(ClO4r (m/z=38Q) and C10H?1NMe3(ClO4)J
(m/z—400'). When extracted with dichloromethane,
municipal potable water samples showed linear
1800
J Sci Food Agric 80:1798-1804 (online: 2000)
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Survey of bottled waters for perchlorate by ESI-MS
lOppb
20ppb
.1?
unspikcd
JVAAJVJUAJL-JUVAJLJUVAJVJ?!'00
5.0 100 is5zrTo
Time (min)
Figure 1. Negative ion ESI-MS injection peaks for Southern Nevada Water
Authority finished water, a supply known to contain perchlorate. The blank
value is obtained without surfactant (no C10H2,NMeJ). Along with the
cationic surfactant, standard additions of 10 and 20ngmr1 are used to
extrapolate to the perchlorate concentration in the water. Two ions are used
to quantitate the perchlorate: C10H21NMe3(Br) (CIO4)- (m/z=380) and
C10H21NMe3(CIO4)J (m/z=400). Note that perchlorate concentration is
related to peak area and not peak height. The relationship between
concentration (amount of analyte injected) and peak area is not
immediately evident because of the shape of the peaks, and integrated
areas must be used. Nearly all (>90%) of the perchlorate is extracted into
the solvent the first time as shown by successive extractions.
increase in peak area with perchlorate concentra-
tion.18'19 For this work, however, MIBKwas chosen as
the solvent to minimize exposure of laboratory
personnel to chlorinated solvents in keeping with
EPA's goals of laboratory safety in test method
development. Partitioning and ionization of the ion
pairs in MIBK is reduced relative to methylene
chloride. This proceduce is sufficient for the purposes
of quantitation, but it requires more careful treatment
of the raw data. The difference in partitioning is
heightened in waters of higher ionic strength because
there is more competition for the decyltrimethyl-
ammonium ion. The best results are obtained by
summing the areas of the two ions, C10H21NMe3(Br)
(ClO4r and C10H21NMe3(ClO4)-. While it may be
possible to mitigate the effect by using more surfac-
tant, there is a significant risk of forming emulsions
and the latter approach was not explored.
Figure 1 shows the flow injection peaks observed for
a water known to contain perchlorate (SNWA).
Making standard additions and monitoring the sum
of the peak areas at m/z = 38Q and 400, we then
extrapolated to the abscissa. This gives the concentra-
tion of perchlorate in the sample in a reasonably
straightforward fashion (Fig 2).
Analytical results
Perchlorate was found only in the water sample from
the Southern Nevada Water Authority. The concen-
tration of the ion obtained using 1C and ESI-MS
methods agreed within the limits of experimental
error. None of the bottled waters tested contained
perchlorate above the lower limit of detection reported
for the 1C method, 5ngml~1. The 1C method is well
established8 and straightforward. Chromatograms for
Aquafina and Naya are shown in Fig 3; recovery is
excellent as shown by the chromatograms of the
fortified samples. For all of the waters, recovery of
the spike by 1C was >98%. Perchlorate was not
detected in any brand of water. For comparison, Fig 4
-50 5 10 15 20 25
Perchlorate concentration (ng ml'1)
Figure 2. Standard addition plots for (Q) Aquafina, (A) Naya, and (V)
SNWA from ESI-MS analysis. The sum of the blank-corrected peak areas
for m/z=380 and 400 are plotted against the added perchlorate
concentration (duplicate spikes at 10 and 20ngmP1). The x-intercept
represents the concentration of perchlorate in the sample.
for SNWA finished water
"1
shows chromatograms
unspiked and spiked with lOngml
Least squares parameters for the standard additions
used in the ESI-MS method are summarized for
bottled waters in Table 2. The ESI-MS method
corroborates the 1C result obtained for the SNWA
sample. For the non-carbonated bottled waters, the
ESI-MS results are consistent with the 1C findings that
perchlorate is below the lower limit of detection, of
approximately Sngml"1. The two naturally carbo-
nated waters show a curious effect: positive abscissal
intercepts, which correspond to negative analyte
concentrations. This non-sensical result is caused by
the high ionic strength of these waters. Although they
were de-gassed prior to analysis to remove CO2, they
contain high levels of dissolved inorganic salts. High
ionic strength interferes with electrospray ionization;
accordingly, signal intensity is diminished. This
produces a negative peak relative to the background
signal of the methanol carrier, which has an ionic
strength approaching zero. In some cases, the problem
can be eliminated by diluting the sample; however, the
lower limit of detection is raised by a factor equal to the
dilution factor. Consequently, there is a trade-off to be
made, and thorough characterization of the matrix is
required to apply this method optimally to waters with
high ionic content. Even with 10% v/v dilutions, we
were unable to successfully quantitate trace perchlo-
rate in Perrier, Pellegrino, or several other sparkling
mineral waters that contain high levels of dissolved
inorganic salts (positive x-intercepts were obtained for
all). Although perchlorate concentrations >200ng
ml"1 can be quantitated in mineral waters, this has
little practical application.
The lower limit of detection (LLOD) for the ESI-
MS method using MIBK is engml""1, based on DI
water standards run at 0, 1.0, 2.0, 4.0, 6.0, 8.0 and
JSci Food Agric 80:1798-1804 (online: 2000)
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ET Urbansky et al
0.8
Aqua Flna Bottlad Watar
0246 8 10 12
(3.) Retention time (min)
Naya Bottlad Watar '
0246 8 10 12
(b) Retention time (min)
Figure 3. Ion chromatograms for
bottled water samples that contain no
perchlorate: (a) Aquaflna and (b) Naya.
Chromatograms for the same samples
fortified with 10ngml~1 perchlorate:
(c) Aquafina and (d) Naya.
Aqua Flna Bottlad Walar
0 2 4 6 8 !0 12
(C) Retention time (m!n)
Naya Bottlad Watar
Spiked to ppb CIO.'
0 2 4 6 8 10 12
(d) Retention time (min)
lO.Ongml l. Eight replicates at 6.0ngml l gave an
estimated standard deviation of O^ngml"1. This
leads to an EPA method detection limit (MDL) of
O.Tngml"1 (using Student's t = 3.500 for the 99%
confidence interval and seven degrees of freedom).
However, a threshold signal distinguishable from the
blank does not occur below 5ngml-1, and so we feel a
minimum reporting level of S-dngml"1 is the most
appropriate.
In addition to the possibility of electrospray sup-
pression, it is worth noting that samples of very high
ionic strength may suffer from a limiting reagent
problem. The post-mixing concentration of the
cationic surfactant is 2.0mM; thus, competition among
anions for the surfactant must be considered. This is
particularly true for less-hydra ted anions, such as
nitrate or bromide, which are extracted into the
MIBK, paired with the surfactant cation. Competition
for the surfactant - to the point of adversely affecting
the analysis — is uncommon with potable water
samples. However, the ESI-MS method cannot readily
be used for beverages such as fruit juices or wines or for
seawater.
Applicability and conclusions
While 1C is likely to be the predominant technique for
determining perchlorate ion concentration in raw and
finished drinking waters (including bottled waters),
ESI-MS provides a useful means of confirming the 1C
identification, which is based on retention time alone.
Capillary electrophoresis or Raman scattering spectro-
metry24'23 may one day play a similar role, but these
techniques are currently not sensitive enough without
pre-concentration (eg with an anion exchange resin or
sample stacking). ESI-MS may be applied to a variety
of drinking water matrices as a confirmatory technique
to support identifications made by 1C. It is reasonably
rugged and reproducible while requiring a minimum
of sample preparation and no separation step prior to
analysis. As with the 1C method, high levels of
05 0.4-
0.2
(a)
5. Nevada Wator Authority
0.0 -]
0246
8 10 12
Retention time (min)
CO 0.4-
0.0-
0
S. Nevada Water Authority
(b)
2 4 6 8 10 12
Retention time (min)
Figure 4. Ion chromatograms for SNWA water (a) unspiked and (b) spiked with 10ngml"1 perchlorate.
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ET Urbansky et al
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