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Butler-Thompson et al.
: J
ournal of
AOAC I
nternational
V
ol.
98, N
o.
6, 2015
INFANT FORMULA AND ADULT NUTRITIONALS
Received April 30, 2015. Accepted by SG June 9, 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:
karen.schimpf@abbott.comDOI: 10.5740/jaoacint.15-107
Determination of Myo-Inositol in Infant, Pediatric, and Adult
Formulas by Liquid Chromatography-Pulsed Amperometric
Detection with Column Switching: Collaborative Study,
Final Action 2011.18
Linda D. Butler-Thompson, Wesley A. Jacobs, and Karen J. Schimpf
1
Abbott Nutrition, 3300 Stelzer Rd, Columbus, OH 43219
Collaborators: J. Austad; L. Basumallick; W.U. Bolong; L. Chen; S. Christiansen; C. Domer; D. Ellingson; G. Lautenschlager;
I. Malaviole; S. Purachaka; G. Wang; F. Xong
AOAC First Action Method 2011.18, Myo-Inositol
(Free and Bound as Phosphatidylinositol) in Infant
and Pediatric Formulas and Adult Nutritionals,
was collaboratively studied. With this method
free myo-inositol and phosphatidylinositol bound
myo-inositol are extracted using two different
sample preparation procedures, separated by ion
chromatography using a combination of Dionex
Carbo Pac PA1 and MA1 columns with column
switching, and detected with pulsed amperometry
using a gold electrode. Free myo-inositol is
extracted from samples with dilute hydrochloric
acid and water. Phosphatidylinositol is extracted
from samples with chloroform and separated from
other fats with silica SPE cartridges. Myo-inositol
is then released from the glycerol backbone with
concentrated acetic and hydrochloric acids at 120°C.
During this collaborative study, nine laboratories
from five different countries analyzed blind
duplicates of nine infant and pediatric nutritional
formulas for both free and phosphatidylinositol
bound myo-inositol, and one additional laboratory
only completed the free myo-inositol analyses.
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 free myo-inositol plus
phosphatidylinositol bound myo-inositol for all the
matrixes analyzed. SMPRs for repeatability were ≤5%
RSD at myo-inositol concentrations of 2–68 mg/100 g
ready-to-feed (RTF) liquid. SMPRs for reproducibility
were ≤8% RSD in products with myo-inositol
concentrations ranging from 2 to 68 mg/100 g RTF
liquid. During this collaborative study, repeatability
RSDs ranged from 0.51 to 3.22%, and RSDs ranged
from 2.66 to 7.55% for free myo-inositol plus
phosphatidylinositol bound myo-inositol.
M
yo-inositol is a water-soluble hydroxylated, cyclic
6-carbon quasi-vitamin. Myo-inositol is regarded as a
quasi-vitamin because it appears to satisfy the criteria
of vitamin status for only a few species or only under certain
conditions. It is the only one of the nine possible stereoisomeric
forms of cyclohexitol with reported biological activity and
is present in nearly all living cells. Myo-inositol occurs in
foods mainly as free myo-inositol, phytic acid, and inositol-
containing phospholipids. Plants seeds are the richest sources
of myo-inositol, but it is present predominantly as phytic acid
which is a poor source of myo-inositol because most mammals
have little or no intestinal phytase activity. Myo-inositol
is present in animal products such as milk, eggs, and meat
primarily as free myo-inositol and phosphatidylinositol (1).
Phosphatidylinositol is also present in soy flour and lecithin.
Although the predominant inositol phosphate in foods is myo-
inositol hexakisphosphate or phytic acid (InsP
6
), other inositol
phosphates such as myo-inositol tris- (InsP
3
), tetrakis- (InsP
4
),
and pentakis- (InsP
5
) phosphate may be present in some foods
in relatively minor amounts (2).
The AOAC Stakeholder Panel on Infant Formula and Adult
Nutritionals (SPIFAN) defined myo-inositol as free myo-inositol
and phosphatidylinositol, excluding methyl ethers, glycosides,
phosphorylated forms, and phytate. Nutritional products are
fortified with free myo-inositol, but they may contain some
inherent free, phosphatidylinositol bound myo-inositol, inositol
phosphates, and phytate. The myo-inositol SPIFAN working
group developed
Standard Method Performance Requirements
(SMPRs
®
) that were then approved by SPIFAN (3).
A reference method capable of determining only free
myo-inositol and myo-inositol bound as phosphatidylinositol
in infant, adult, and pediatric formula powders; ready-to-
feed (RTF) liquids; and liquid concentrates was needed since
there were no myo-inositol reference methods. Traditional
microbiological methods are not precise and accurate enough
to meet the nutrient specification requirements of infant,
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