With the globalization of our food supply, food safety and quality have become great concerns for both consumers and regulatory bodies. Sugars and organic acids, for example, influence the organoleptic properties of many products. They must be identified and analyzed in raw ingredients and throughout the production process, all the way to final quality control and nutritional labeling.
Water is a crucial reagent in the IC workflow as it is required in many steps, including the preparation of samples, standards, blanks, and eluents. To ensure accurate and reliable IC analysis, the water used should be of the highest quality level and be free of the analytes of interest. Any contaminant present in the water may impact results and should be avoided.
In this app note, you’ll learn about:
- Suitability of ultrapure water for the IC analysis of food and beverages
- Quantification of sugars in ultrapure water
- Quantification of small organic acids in ultrapure water
- And more!
Application Note
Ultrapure Water for Food and Beverage
Analysis by Ion Chromatography
Authors
Merina Corpinot PhD
1
, Estelle Riche PhD
2
, Beatrice Frocrain
1
, Stephane Mabic PhD
2
R&D
1
and Marketing
2
, Lab Water Solutions, MilliporeSigma, Guyancourt, France
Ion chromatography in quality
assurance & quality control of food
and beverages
One of the main challenges in food and beverage
testing is detecting trace amounts of analytes in
complex matrices. Ion chromatography (IC) is
increasingly used in food and beverage Quality
Assurance/Quality Control (QA/QC) laboratories since
it is a versatile and sensitive analytical method that
allows the simultaneous analysis of a wide array
of compounds.
Analyzing sugars to monitor food safety
& food authenticity
With the globalization of our food supply, food
safety and quality have become great concerns for
both consumers and regulatory bodies. Sugars and
organic acids, for example, in?uence the organoleptic
properties of many products. They must be identi?ed
and analyzed in raw ingredients and throughout the
production process, all the way to ?nal quality control
and nutritional labeling. In addition, pro?ling the sugar
makeup of foods and identifying additives is a useful
way to assess food authenticity and detect adulteration.
Water is a crucial reagent in the IC work?ow as it is
required in many steps, including the preparation of
samples, standards, blanks and eluents. To ensure
accurate and reliable IC analysis, the water used
should be of the highest quality level and be free of the
analytes of interest. Any contaminant present in the
water may impact results and should be avoided.
Suitability of ultrapure water for the IC
analysis of food and beverages
This study examines the suitability of ultrapure water
obtained from a Milli-Q
®
IQ 7000 ultrapure water
puri?cation system for the IC analysis of sugars and
small organic acids commonly assessed in food and
beverage testing labs.
Quanti?cation of sugars in ultrapure water
Sugars are important for human nutrition and must
be analyzed for nutritional labeling and to monitor
product quality. Lactose is carefully monitored in many
products, especially those claiming to be lactose-free.
Sugars are also good indicators of the ?avor of drinks,
such as beer or co?ee.
High-performance anion-exchange chromatography
with pulsed amperometric detection (HPAE-PAD)
is an increasingly used IC method that allows the
direct and sensitive quanti?cation of a wide range of
carbohydrates at low nanomolar levels without the
need for derivatization.
1,2
Obtaining reliable, consistent and accurate results
requires water that is free of the analytes of interest.
Using HPAE-PAD, freshly produced ultrapure water
obtained from the Milli-Q
®
IQ 7000 system was
analyzed for the presence of common monosaccharides
(fructose, glucose) and disaccharides (sucrose,
maltose, lactose). Table 1 shows that the ultrapure
water contained less than the method’s quanti?cation
limit (1 mg/L) of each of the sugars. This water is
therefore suitable to be used in sample and eluent
preparation, as well as standard preparation for
sugar analyses.
MilliporeSigma is the U.S. and Canada
Life Science business of Merck KGaA,
Darmstadt, Germany.
2
Sugar Ultrapure water LOQ (mg/L)
Glucose < LOQ 1.0
Fructose < LOQ 1.0
Sucrose < LOQ 1.0
Maltose < LOQ 1.0
Lactose < LOQ 1.0
Small organic acid Ultrapure water LOQ (mg/L)
Citric acid < LOQ 1.0
Malic acid < LOQ 1.0
Tartaric acid < LOQ 1.0
Lactic acid < LOQ 0.2
Acetic acid* < LOQ 0.003
Formic acid* < LOQ 0.002
Table 1. Concentrations of various sugars in ultrapure water obtained
from a Milli-Q
®
IQ 7000 ultrapure water puri?cation system. Samples
were tested by an independent, accredited laboratory. LOQ, Limit of
Quanti?cation.
Table 2. Concentrations of small organic acids in ultrapure water
delivered from a Milli-Q
®
IQ 7000 ultrapure water puri?cation system.
Samples were tested by an independent, accredited laboratory, except
for acetic and formic acids (*), which were tested in-house after pre-
concentration. LOQ, Limit of Quanti?cation.
Conclusion: Milli-Q
®
ultrapure water
meets the needs of food and beverage
ion chromatography analyses
When analyzing foods or beverages, high quality
reagents should be used throughout the analytical
work?ow, from the preparation of standards and
samples to analysis, as the presence of contaminants
can a?ect results. In this study, ultrapure water
dispensed from a Milli-Q
®
IQ 7000 lab water system
was shown to be e?ectively free of commonly analyzed
sugars and organic acids, making this water ideal for
the IC analysis of food and beverage samples.
Ultrapure water is also free of other contaminants,
such as inorganic ions, bacteria and particles, that may
a?ect the performance of the analytical instrument
itself. Instrument manufacturers have observed that
the HPAE-PAD chromatographic technique is more
sensitive to certain water contaminants compared with
other analytical techniques.
3
For example, if the eluent
is prepared using bacteria-contaminated water, high
background signals may reduce the peak areas of the
analytes of interest. Furthermore, extra peaks may
be observed if such water is used to prepare samples
for this method. For this reason, when dispensing
ultrapure water from a Milli-Q
®
ultrapure water system,
the Millipak
®
0.22 μm ?nal ?lter is highly recommended
to remove these critical contaminants.
This study demonstrates that ultrapure water freshly
produced by a Milli-Q
®
IQ 7000 water puri?cation
system is suitable for IC analysis of sugars and small
organic acids. A Milli-Q
®
IQ 7000 ultrapure water
puri?cation system can be fed by a Milli-Q
®
IX pure
water system. Alternatively, it is possible to use
the Milli-Q
®
IQ 7003/05/10/15 all-in-one pure and
ultrapure system, which also dispenses ultrapure
water suitable for IC analysis using tap water as its
feed source.
The Milli-Q
®
IQ 7000 system produces ultrapure
water suitable for ion chromatography.
Quanti?cation of small organic acids in
ultrapure water
Small organic acids in?uence the taste and aroma
of foods and drinks. These acids may be present
naturally, or may be added in order to enhance a
product’s tartness and acidity, stabilize the pH, or act
as a preservative. Tartaric, citric and malic acids are
closely monitored in wine, beer and fruit juices. They
have organoleptic properties and are good indicators
of quality. Acetate and lactate, on the other hand, are
often used as indicators of microbiological spoilage,
for example in fruit juices. In soft drinks, citrate and
malate are monitored as they act as acidi?ers or
?avor enhancers.
We analyzed freshly produced ultrapure water
dispensed from a Milli-Q
®
IQ 7000 water system for
the presence of the above organic acids by IC with
suppressed conductivity detection. Table 2 shows
that the ultrapure water did not contain measurable
ion concentrations of citric, malic, tartaric or lactic
acid, as determined by an independent laboratory.
Acetic and formic acid levels were measured in-house
after pre-concentration. Results showed that their ion
concentrations were also below the method’s limit of
quanti?cation (LOQ). Ultrapure water from a Milli-Q
®
IQ 7000 system is therefore suitable for use in sample
preparation and organic acid analysis of foods and
beverages by IC.
Experimental section
Samples tested
Ultrapure water dispensed from a Milli-Q
®
IQ 7000
water puri?cation system (Resistivity: 18.2 MΩ.cm at
25 °C, TOC < 5 ppb) ?tted with a 0.22 µm ?nal ?lter
(Millipak
®
) and fed by an Elix
®
electrodeionization
(EDI)-based pretreatment system similar to the Milli-Q
®
IX pure water system.
Analysis of sugars
• Glucose, fructose, sucrose, maltose and lactose
were analyzed by an independent, accredited
(COFRAC) laboratory.
• Instrument: Thermo Scienti?c Dionex™ ICS-5000+
• Analytical Column: CarboPac™ PA1, 4 x 250 mm
• Eluent: NaOH gradient (A: 50 mM of NaOH and
B: 100 mM NaOH, both prepared with water from a
Milli-Q
®
ultrapure water system)
• Detection: Pulsed amperometry
Analysis of small organic acids
1. Citric, malic, tartaric, and lactic acids were analyzed
by an independent accredited (COFRAC) laboratory.
• Instrument: Thermo Scienti?c Dionex™ ICS-5000+
• Analytical column: IonPac™ AS 11-HC
• Eluent: NaOH gradient 1 to 60 mM (NaOH
solutions prepared with water from a Milli-Q
®
ultrapure water system)
• Detection: Suppressed conductivity
2. Acetic and formic acids were analyzed (after pre-
concentration) in our R&D laboratories.
• Instrument: Thermo Scienti?c Dionex™ ICS-3000
• 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
References
1. Corradini C, Cavazza A, Bignardi C. High-Performance
Anion-Exchange Chromatography Coupled with Pulsed
Electrochemical Detection as a Powerful Tool to Evaluate
Carbohydrates of Food Interest: Principles and Applications.
Int J Carbohydr Chem 2012;2012:1-13. https://doi.
org/10.1155/2012/487564
2. Jahnel JB, Ilieva P, Frimmel FH. HPAE-PAD - A sensitive method
for the determination of carbohydrates. Fresenius J of Anal Chem
1998;360:827-9. https://doi.org/10.1007/s002160050819
3. Rohrer J. Eluent Preparation for High-Performance Anion-Exchange
Chromatography with Pulsed Amperometric Detection. Technical
Note 71. Thermo Fisher Scienti?c, Sunnyvale, CA, USA. 2017.
• Sample volumes: 100 mL
• Standards: TraceCERT
®
standards
• 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 by direct-feed from an ICW-
3000™ water puri?cation system; ?ow rate:
0.25 mL/min
• Detection: Suppressed conductivity; eluent
suppressor: ASRS
®
Ultra II 2 mm
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.
TraceCERT
®
Acetate Standard for IC
51791
TraceCERT
®
Tartrate Standard for IC
43484
Products related to this article
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02/2023
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