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198
B
olong
et al
.:
J
ournal of
AOAC I
nternational
V
ol
.
99, N
o
.
1, 2016
Infant Formula and Adult Nutritionals
A potentiometric method for determination of chloride
was validated against AOAC
Standard Method
Performance Requirement
(SMPR
®
) 2014.015. Ten
AOAC Stakeholder Panel on Infant Formula and
Adult Nutritionals (SPIFAN) matrixes, including
National Institute of Standards and Technology
(NIST) Standard Reference Material (SRM) 1849a,
were tested in duplicate on 6 independent days.
The repeatability (RSD
r
) ranged from 0.43 to 1.34%,
and the intermediate reproducibility (RSD
iR
) ranged
from 0.80 to 3.04%. All results for NIST SRM 1849a
were within the range of the certified concentration
(701±17 mg/100 g). Recovery was demonstrated
with two overspike levels, 50 and 100%, in the
10 SPIFAN matrixes. Samples were tested in duplicate
on 3 different days, and all results were within the
SMPR requirement of 95 to 105%. The LOQs of the
method for powdered products and ready-to-feed
or reconstituted products were 20 mg/100 g and
2.2 mg/100 mL, respectively. A wide analytical range
from the LOQ to 99.5% chlorine content can be
reached with an appropriate dilution factor, but in
practice, the upper analytical value observed
in routine matrix testing was approximately
1080 mg/100 g in skim milk powder. This is a
rapid, simple, and reliable chlorine-testing method
applicable to infant formula, adult nutritionals, and
ingredients used in these dairy-based products, such
as skim milk powder, desalted whey powder, whey
protein powder, and whole milk powder.
I
n response to a need for a reference method for dispute
resolution, the AOAC Stakeholder Panel on Infant Formula
and Adult Nutritionals (SPIFAN) developed
Standard
Method Performance Requirement
(SMPR
®
) 2014.015,
“
Standard Method Performance Requirements
for Determination
of Chloride in Infant and Adult/Pediatric Nutritional
Formula” (1). National Food Safety Standard GB 5413.24-2010,
“Determination of chlorine in foods for infants and young
children, milk and milk products,” is a Chinese nationally
enforced testing method published by the Ministry of Health in
2010 as Notice 7. The notice includes 66 national standards in
the area of dairy products and forms the regime of Chinese dairy
product safety national standards. There are two methods within
GB 5413.24-2010: one is a potentiometric titration method,
and the other is a traditional titration method using a color
indicator to determine the end of titration. The potentiometric
titration method in GB 5413.24-2010 has a limitation in the end
point determination or in precise titrant volume recording due
to being an older titration technique using older instrumental
analysis. A new potentiometric titration method was therefore
developed at the Comprehensive Test Center of Chinese
Academy of Inspection and Quarantine (CAIQTEST), which
applied a modern, sophisticated, automatic titration system for
enhancing the precision, accuracy, and efficiency of testing. It is
a high-throughput, practical method that can be used in routine
testing.
CAIQTEST is a national institute under the leadership of
Chinese Academy of Inspection and Quarantine (CAIQ) and
operating as a third-party inspection agency in accordance
with ISO/IEC 17025. CAIQ is a national public institute for
researching and developing science and technology to be
applied in inspection and quarantine. The mission of CAIQ is
mainly to conduct research on the applied science of inspection
and quarantine, as well as basic, high-tech, and soft science,
with the focus on solving general and comprehensive problems
and emergent and pivotal issues related to the administration
of inspection and quarantine. CAIQ provides technical support
to the policy making related to inspection and quarantine for
China’s central government, and provides technical assistance
to the law enforcement duties of the General Administration of
Quality Supervision, Inspection, and Quarantine.
Single-Laboratory Validation Study
The validation study compared the results of the method
to the criteria of AOAC SMPR 2014.015. The requirements
are presented in Table 1. Validation experiments included
determination of system suitability, precision, accuracy, LOQ,
and analytical range of the method.
Determination of Chloride in Infant Formula and Adult/
Pediatric Nutritional Formula by Potentiometric Titration:
Single-Laboratory Validation, First Action 2015.07
W
u
B
olong
,
Z
hang
F
engxia
,
1
M
a
X
iaoning
, and
Z
hou
F
engjuan
Comprehensive Test Center of Chinese Academy of Inspection and Quarantine, Gao Bei Dian North Rd A3, Chao Yang District,
Beijing, People’s Republic of China
S
haron
L. B
runelle
Brunelle Biotech Consulting, 14104 194th Ave NE, Woodinville, WA 98077
Received June 01, 2015. Accepted by AK July 08, 2015.
This method was approved by the Expert Review Panel for Infant
Formula and Adult Nutritionals as First Action.
The Expert Review Panel for Infant Formula and Adult Nutritionals
invites method users to provide feedback on the First Action methods.
Feedback from method users will help verify that the methods are
fit-for-purpose and are critical for gaining global recognition and
acceptance of the methods. Comments can be sent directly to the
corresponding author or
methodfeedback@aoac.org.1
Corresponding author’s e-mail:
zhangfengxia@caiqtest.comDOI: 10.5740/jaoacint.15-0143
80