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Pacquette & Thompson
: J
ournal of
AOAC I
nternational
V
ol.
98, N
o.
6, 2015
INFANT FORMULA AND ADULT NUTRITIONALS
Received on May 27, 2015. Accepted by SG June 15, 2015.
The method was approved by the AOAC
Official Methods Board
as Final Action.
See
“Standards News,” (2014)
Inside Laboratory
Management
, November/December issue.
The AOAC Stakeholder Panel on Infant Formula and Adult
Nutritionals (SPIFAN) invites method users to provide feedback on the
Final Action methods. Feedback from method users will help verify
that the methods are fit for purpose and are critical to gaining global
recognition and acceptance of the methods. Comments can be sent
directly to the corresponding author.
1
Corresponding author’s e-mail:
joseph.thompson@abbott.comDOI: 10.5740/jaoacint.15-139
Determination of Chromium, Selenium, and Molybdenum in
Infant Formula and Adult Nutritional Products by Inductively
Coupled Plasma/Mass Spectrometry: Collaborative Study,
Final Action 2011.19
Lawrence H. Pacquette and Joseph J. Thompson
1
Abbott Nutrition, 3300 Stelzer Rd, Columbus, OH 43219
Collaborators: M. Farrow, M. Feller, Y. Fenpeng, M. Gray, I. Malaviole, A. Mittal, D. Mould, F. Xiang, S. Yadlapalli, S. Zhang,
Y. Zhang
AOAC First Action Method 2011.19: Chromium,
Selenium, and Molybdenum in Infant Formula and
Adult Nutritional Products, was collaboratively
studied. This method uses microwave digestion of
samples with nitric acid, hydrogen peroxide, and
internal standard followed by simultaneous detection
of the elements by an inductively coupled plasma
(ICP)/MS instrument equipped with a collision/
reaction cell. During this collaborative study, nine
laboratories from four different countries, using seven
different models of ICP/MS instruments, analyzed
blind duplicates of seven infant, pediatric, and adult
nutritional formulas. One laboratory’s set of data was
rejected in its entirety. The method demonstrated
acceptable repeatability and reproducibility and
met the AOAC Stakeholder Panel on Infant Formula
and Adult Nutritionals (SPIFAN)
Standard Method
Performance Requirements
(SMPRs
®
) for almost
all of the matrixes analyzed. The Cr, Mo, and Se
SPIFAN requirement for repeatability was ≤5% RSD.
The SMPR called for a reproducibility of ≤15% RSD
for products with ultratrace element concentrations
above the targeted LOQ of 20 µg/kg
Cr/Mo and 10 µg/kg Se (as ready-to-feed). During this
collaborative study, RSD
r
ranged from 1.0 to 7.0%
and RSD
R
ranged from 2.5 to 13.4% across all three
ultratrace elements.
M
ost infant formulas are fortified with the essential
trace element selenium (Se); many pediatric and adult
nutritional products are also fortified with chromium
(Cr) and molybdenum (Mo; 1, 2). Together these ultratrace
elements represent some of the most difficult analyses for any
laboratory testing against the relatively narrow specification
ranges mandated by many regulatory bodies for these added
nutrients in infant and pediatric formulas. Existing official
methods that have been specifically validated for Cr, Mo, and
Se in infant and pediatric nutritional products were virtually
nonexistent until theAOAC Stakeholder Panel on Infant Formula
and Adult Nutritionals (SPIFAN) issued a Call for Methods
in 2011 and a suitable method was put forward that was already
being used in the authors’ laboratory (3). This method appeared
to have the requisite precision, accuracy, and ruggedness for
ultratrace element analysis based upon successful completion
of an internal single-laboratory validation (SLV). The SPIFAN
Working Group had formulated a set of
Standard Method
Performance Requirements
(SMPRs
®
) that captured the needs of
the formula manufacturers for a suitable global dispute resolution
method for ultratrace element analysis. SMPRs were approved
by stakeholders (4), and the AOAC Expert Review Panel (ERP)
on SPIFAN Nutrient Methods approved only this method as First
Action in 2011 (AOAC
2011.19
) because it appeared to meet the
SMPRs on that manufacturer’s own products. However, the ERP
requested the SLV be repeated with the specific set of SPIFAN
matrixes developed to be representative of most of the other
manufacturers’ products. After examining the second set of SLV
data, the ERP voted that the method proceed to a multilaboratory
testing (MLT) of reproducibility. These latter SLV data have not
been published before and are captured in this report with the
subsequent MLT collaborative data usingAOACmethod
2011.19
.
Multilaboratory Collaborative Study
Initially 16 laboratories expressed interest in participating in
the AOAC
2011.19
ultratrace element collaborative study, but
only nine laboratories were able to complete the study because
of lack of time or resources, or they could not import the samples
in due time. The nine participating laboratories were located in
four different countries (China, United States, India, and France)
and were equipped with seven different models of inductively
coupled plasma (ICP)/MS instruments, namely the PerkinElmer
(Shelton, CT) ELAN DRC-e, ELAN DRC II, and NexION 300D;
the Agilent (Santa Clara, CA) 7700x and 7500cx (the latter
used only during the authors’ SLV); and the Thermo Scientific
(Waltham, MA) iCAP Q and X Series 2. All these instruments
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