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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.com

DOI: 10.5740/jaoacint.15-0143

80