Water is the lifeline of our well-being, and its purity is of utmost importance. With strict regulations in place, it's crucial to ensure the highest quality of our drinking water. However, did you know that inorganic ions present in water can pose health risks? On the other hand, certain ions can significantly impact the taste and sensory experience of water.
By employing the highest quality water as a key reagent, you can unlock accurate and dependable IC results. Our application note provides expert guidance, revealing the best practices and essential tips for obtaining reliable outcomes.
Download the application note now to learn more about using ultra pure water for your IC analyses.
Application Note
Ion chromatography for drinking
water analysis
Ion chromatography (IC) is a common analytical
technique to test water samples for contaminants.
Puri?ed water is used in multiple steps of the IC
work?ow. For example, to prepare samples, standards
and blanks, as well as for water-based eluents. Water
is therefore a key reagent and should be of the highest
quality to obtain accurate and reliable IC results.
In this article, we assess the suitability of ultrapure
water produced by a Milli-Q
®
IQ 7000 water puri?cation
system for the IC analyses of inorganic ions and DBPs
in drinking water.
IC analysis of ions in ultrapure and
drinking water samples
We analyzed tap water and ultrapure water that was
freshly delivered by a Milli-Q
®
IQ 7000 system. This
puri?cation system delivers water with resistivity of
18.2 MOhm.cm at 25 °C and total organic carbon (TOC)
< 5 ppb. The system was fed with pure water from an
Elix
®
electrodeionization (EDI)-based system and ?tted
with a 0.22 µm Millipak
®
?nal ?lter.
Inorganic ion concentrations assessed in the ultrapure
water were either not detectable or were below the
limit of detection (LOD). For example, nitrate (NO
3
-
)
levels in the ultrapure water were 140,000-fold
lower than the lowest limits de?ned by the WHO and
European regulatory bodies. This was observed even
though the tap water feeding the water puri?cation
chain contained large amounts of these ions (Table 1).
Drinking Water Testing by Ion
Chromatography using Ultrapure Water
Authors:
Merina Corpinot Ph.D.
1
, Estelle Riche Ph.D.
2
, Beatrice Frocrain
1
, Cecilia Devaux
1
, Stephane Mabic Ph.D.
2
R&D
1
and Marketing
2
, Lab Water Solutions, MilliporeSigma, Guyancourt, France
Drinking water is the most essential beverage for our
health, therefore its quality is strictly regulated.
1,2
Inorganic ions in water can be detrimental to health (e.g.,
nitrates and nitrites), while other ions may in?uence
water’s organoleptic properties. For example, chloride and
sulfate ions may induce a noticeable, unpleasant taste.
Water is frequently treated with chemicals to control
bacteria and remove pathogens. These chemicals can
generate harmful disinfection by-products (DBPs) when
they react with organic molecules naturally present in
water.
3
For these reasons, ion and DBP concentrations
in drinking water are highly monitored and controlled,
and techniques are constantly evolving to accurately
detect and quantify them.
MilliporeSigma is the U.S. and Canada
Life Science business of Merck KGaA,
Darmstadt, Germany.
2
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Figure 1 and Figure 2 show ion chromatograms of
ultrapure water compared to those of anionic and
cationic standard mixtures, respectively.
Figure 1. Ion chromatograms of ultrapure water from a Milli-Q
®
IQ
7000 water puri?cation system and of a mix of anionic standards.
Peak 9: carbonate
Figure 2. Ion chromatograms of ultrapure water from a Milli-Q
®
IQ
7000 system and of a mix of cationic standards.
Table 1. Concentration of anions and cations in tap water (Guyancourt, France) and ultrapure water
determined by IC analysis and compared to limits set by regulatory bodies.
Ions Diluted tap water* Ultrapure water LOD / LOQ WHO guidelines
2
FDA SOQ
4
/EPA MCL
5
EU directive
1
F
-
(µg/L) 0.15 < LOD 0.02 / 0.06 1 500 Variable/4 000 1 500
Cl
-
(µg/L) 22.67 n.d. 0.17 / 0.51 - 250 000 250 000
NO
2
-
(µg/L) < LOD n.d. 0.16 / 0.49 3 000 1 000 500 000
NO
3
-
(µg/L) 34.55 n.d. 0.36 / 1.08 50 000 10 000 50 000
SO
4
2-
(µg/L) 52.48 n.d. 0.84 / 2.55 - 250 000 250 000
Na
+
(µg/L) 16.56 < LOD 0.17 / 0.53 - n/a 200 000
K
+
(µg/L) 2.52 < LOD 0.16 / 0.49 - n/a n/a
Mg
2+
(µg/L) 5.01 < LOD 0.06 / 0.18 - n/a n/a
Ca
2+
(µg/L) 106.06 < LOD 0.07 / 0.22 - n/a n/a
*Tap water was diluted 1000-fold with ultrapure water prior to analysis. Ultrapure water was delivered from a Milli-Q
®
IQ 7000 system. EPA, US
Environmental Protection Agency; FDA, US Food and Drug Administration; LOD, Limit of Detection of the method; LOQ, Limit of Quanti?cation;
MCL, Maximum Contaminant Level; n/a, no data available; n.d., not detected; SOQ, Standards of Quality; WHO, World Health Organization;
-, Not a health concern found in drinking water.
These results demonstrate that freshly delivered
ultrapure water from a Milli-Q
®
IQ 7000 system is
well-suited for use in IC analysis. This water may
con?dently be used for blanks and to preparate samples,
standards and eluents. Ultrapure water from the system
is also suitable to analyze drinking water as it contains
extremely low levels of inorganic ions.
Experimental method
For inorganic anions:
• Instrument: Thermo Scienti?c Dionex™
ICS-3000 system
• Columns: Anion concentrator: IonPac™ UTAC-ULP1
5 x 23 mm; Guard column: IonPac™ AG19 2 x
50 mm; Analytical column: IonPac™ AS19 2 x
250 mm
• Eluent: KOH gradient: 1 to 35 mM KOH from 0 to
20 min; 35 mM from 20 to 25 min; 35 to 1 mM from
25 to 25.1 min; 1 mM from 25.1 to 30 min
• Eluent source: EG40 with KOH cartridge and
ultrapure water from an ICW-3000™ direct IC feed
system; Flow rate: 0.25 mL/min
• Detection: Suppressed conductivity; Eluent
suppressor: ASRS
®
Ultra II 2 mm
• Samples and standards: sample volume was 40 mL
(pre-concentrated: 40 mL sample is concentrated on
a cartridge, and the concentrated sample is injected
on a column after desorption). TraceCERT
®
standards
were used.
For inorganic cations, the same method was used, but
with an MSA gradient and a CS12A analytical column.
Mix of standards
1. F
-
0.5 µg/L
2. Lactate 2 µg/L
3. Acetate 2 µg/L
4. Formate 2 µg/L
5. Cl
-
1 µg/L
6. NO
2
-
4 µg/L
7. Br 4 µg/L
8. NO
3
-
4 µg/L
10. SO
4
2-
4 µg/L
11. Malonate 2 µg/L
12. Oxalate 2 µg/L
13. I
-
1 µg/L
14. PO
4
3-
6 µg/L
1
2
3
4
5
6
7
Mix of standards
1. Li
+
0.5 µg/L
2. Na
+
1 µg/L
3. NH
4
+
1 µg/L
4. K
+
2 µg/L
5. Mg
2+
1 µg/L
6. Mn
2+
1 µg/L
7. Ca
2+
2 µg/L
3
IC analysis of disinfection by-products in ultrapure and drinking water samples
To maintain safe drinking water, a critical amount of
disinfectant must be added to kill pathogens while also
minimizing the production of DBPs to levels that are
below acceptable limits.
The EPA
5
and WHO
2
have set the maximum level of
bromate permissible in tap water at 10 μg/L. The FDA
adopts this same regulatory limit for bottled water.
4
In Europe, natural mineral waters and spring waters
treated by ozonation have a maximum permissible
bromate limit of 3 μg/L
6
; this value is 10 µg/L for
drinking water.
1
Levels of bromate, chlorate and
chlorite in drinking water are commonly assessed by IC
following EPA method 300.1.
7
We analyzed tap water and ultrapure water freshly
delivered from a Milli-Q
®
IQ 7000 system equipped
with a Millipak
®
?nal ?lter. Bromate, chlorate and
chlorite levels in the ultrapure water were below the
limits set by regulatory bodies (Table 2). Even if some
DBPs were present in the feed tap water, DBPs were
not detected in the ultrapure water dispensed from
the system.
The combination of technologies in the water
puri?cation chain (consisting of an Elix
®
EDI-based
system feeding a Milli-Q
®
IQ 7000 system) e?ciently
removes trace levels of DBPs to produce ultrapure
water that is suitable for drinking water analysis by IC.
Experimental method
Analyses were performed by an independent accredited
(COFRAC) laboratory.
• Chlorite and chlorate: according to norm NF EN ISO
10304-4
• Bromate: according to norm NF EN ISO 15061
• Eluent: carbonate/bicarbonate
• Column: Metrohm Metrosep A supp 7 – 250/4.0,
45 °C, suppressed conductivity detection
Table 2. Quanti?cation of DBPs in tap water (Guyancourt, France) and ultrapure water determined by
IC analysis, and compared to regulatory bodies limits for drinking water.
DBP Tap water Ultrapure water LOQ WHO guidelines
2
FDA SOQ
4
/ EPA MCL
5
EU directive
1
Bromate (µg/L) 1 < LOQ 1 10 10 10
Chlorate (µg/L) 35 < LOQ 10 700 n/a 250
Chlorite (µg/L) < LOQ < LOQ 10 700 1 000 250
Suitability of ultrapure water produced by a Milli-Q
®
water puri?cation system for
the IC analysis of drinking water
This study demonstrates that ultrapure water freshly
produced by a Milli-Q
®
IQ 7000 water puri?cation
system is suitable for the tasks performed as part of
the IC analysis of drinking water. Speci?cally, for the
preparation of eluents, samples, and standards, and for
use as blanks. Even if the tap water feeding the system
contains the ions to be measured, these contaminants
are removed by the combination of technologies
present in the water puri?cation chain.
A Milli-Q
®
IQ 7000 ultrapure water system can be fed
by an Milli-Q
®
IX pure water system, which includes
Elix
®
EDI technology. Alternatively, a Milli-Q
®
IQ
7003/05/10/15 pure and ultrapure system dispenses
ultrapure water suitable for IC analysis using tap water
as its feed source.
Samples were tested by an independent accredited laboratory. Ultrapure water was delivered from a Milli-Q
®
IQ 7000 water puri?cation system.
EPA, US Environmental Protection Agency; FDA, US Food and Drug Administration; LOQ, Limit of Quanti?cation; MCL, Maximum Contaminant
Level; n/a, no data available; SOQ, Standards of Quality; WHO, World Health Organization.
References
1. Communities O?cial Journal of the European. Directive (EU)
2020/2184 of the European Parliament and of the Council of
16 December 2020 on the quality of water intended for human
consumption. 2020 eur-lex.europa.eu/eli/dir/2020/2184/oj
2. World Health Organization. Guidelines for drinking-water quality:
fourth edition incorporating ?rst addendum. who.int/publications/i/
item/9789241549950
3. Gilchrist ES, Healy DA, Morris VN, Glennon JD. A review of
oxyhalide disinfection by-products determination in water by ion
chromatography and ion chromatography-mass spectrometry. Anal
Chim Acta 2016;942:12–22. doi.org/10.1016/j.aca.2016.09.006
4. CFR - Code of Federal Regulations Title 21. accessdata.
fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.
cfm?fr=165.110&SearchTerm=bottled%20water
5. National Primary Drinking Water Regulations | US EPA. epa.gov/
ground-water-and-drinking-water/national-primary-drinking-
water-regulations#two
6. COMMISSION DIRECTIVE 2003/40/EC of 16 May 2003 establishing
the list, concentration limits and labelling requirements for
the constituents of natural mineral waters and the conditions
for using ozone-enriched air for the treatment of natural
mineral water. eur-lex.europa.eu/legal-content/EN/TXT/
PDF/?uri=CELEX:32003L0040&from=FR
7. Pfa? JD, Hautman DP, Munch DJ. Method 300.1: Determination of
inorganic anions in drinking water by ion chromatography. Stand
Methods 1999;1–40.
Products related to this article:
Water puri?cation systems and solutions Cat. No.
Milli-Q
®
IQ 7000 ultrapure water puri?cation system ZIQ7000T0C
Milli-Q
®
IQ 7003 pure and ultrapure water puri?cation system ZIQ7003T0C
Milli-Q
®
IQ 7005 pure and ultrapure water puri?cation system ZIQ7005T0C
Milli-Q
®
IQ 7010 pure and ultrapure water puri?cation system ZIQ7010T0C
Milli-Q
®
IQ 7015 pure and ultrapure water puri?cation system ZIQ7015T0C
Millipak
®
0.22 μm ?lter MPGP002A1
Reference standards Cat. No.
Fluoride Standard for IC, TraceCERT
®
, 1000 mg/L ?uoride in water 77365
Nitrate Standard for IC, TraceCERT
®
, 1000 mg/L nitrate in water 74246
Potassium Standard for IC, TraceCERT
®
, 1000 mg/L K
+
in water 53337
Calcium Standard for IC, TraceCERT
®
, 1000 mg/L Ca
2+
in nitric acid 39865
MS_AN9589EN Ver. 1.0
41690
07/2022
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