AOACSPIFANMethods-2017Awards

Butler-Thompson et al.

: J

ournal of

AOAC I

nternational

ol.

98, N

6, 2015

1677

(b)

Preparation of standard curve.—

For each working

standard concentration, average the peak areas or heights from

each of two consecutive sets of standards. Prepare a standard

curve by performing linear least squares regression on the

concentrations versus the averaged peak areas or heights.

A standard curve must have a correlation of at least 0.999 to be

considered acceptable for sample calculations.

At each working standard level, the peak areas or heights of

standards injected before and after a set of samples must not

increase or decrease by more than 7%.

(c)

Calculationofmyo-inositolinsamples.

—Theconcentration

of myo-inositol in a prepared sample is extrapolated from the

standard curve prepared above. From the diluted, prepared sample

concentration, the product concentration can be calculated:

= (C

× D

)/S

where C

is the concentration of myo-inositol in the product

sample in mg/kg, C

is the concentration of myo-inositol in the

prepared sample in mg/L, D

is the dilution volume in mL, and

S is the sample weight in g.

Note

: For each set of samples, the control result must be

within 3 SDs of the control mean.

Results and Discussion

All of the free, phosphatidylinositol bound, and free

plus phosphatidylinositol bound myo-inositol collaborative

study data are summarized in Tables 1–9. It should be

noted that laboratory 5 did not receive the liquid RTF study

samples and that laboratory 6 was not able to complete the

phosphatidylinositol bound myo-inositol testing.

Using the AOAC INTERNATIONAL Interlaboratory Study

Blind (Unpaired) Replicates Workbook (7), statistical outliers

from one or two laboratories were identified in five of the nine

products analyzed for free plus phosphatidylinositol bound myo-

inositol content. After removal of outliers, RSD

ranged from

0.51 to 3.22% and met the SMPR of ≤5% for all the products

analyzed. The RSD

ranged from 2.83 to 7.55% and met the

SMPR of ≤8% for all the products analyzed. When the outliers

were included, RSD

ranged from 0.91 to 4.67%, meeting the

SMPR of ≤5% for all the products analyzed, and the RSD

ranged from 2.83 to 11.2%, meeting the SMPR of ≤8% for eight

of the nine products analyzed.

Since it is possible that some laboratories may only use this

method for free myo-inositol analyses, a review of the free

myo-inositol collaborative data is also included here. Using

the AOAC INTERNATIONAL Interlaboratory Study Blind

(Unpaired) Replicates Workbook, statistical outliers from one

or two laboratories were identified in five of the nine products

analyzed for free myo-inositol content. After removal of free

myo-inositol outliers, RSD

ranged from 0.46 to 3.03% and

met the SMPR of ≤5% for all the products analyzed. The

RSD

ranged from 2.15 to 12.6% and met the SMPR of ≤8%

for eight of the nine products analyzed. When the outliers were

included in the free myo-inositol data summary, RSD

ranged

from 0.97 to 4.45%, still meeting the SMPR of ≤5% for all the

products analyzed, and the RSD

ranged from 2.77 to 12.6%

and met the SMPR of ≤8% for seven of the nine products

analyzed.

Several laboratories provided comments about the method.

Some laboratories made positive comments regarding the

column switching format because it saved time and kept the

electrode clean, while other laboratories would prefer using

a gradient rather than column switching. One laboratory

questioned the need for determining the phosphatidylinositol

component. As noted previously, some laboratories had to use

a higher temperature than that listed in the method to improve

recoveries of phosphatidylinositol boundmyo-inositol, and some

laboratories had trouble adding 50% sodium hydroxide directly

to the samples immediately after hydrolysis. One laboratory

recommended adding additional guidance for determining the

amount of acid needed to adjust the pH of a sample to 4.5 for

free myo-inositol analyses and for determining the percentage

recovery of phosphatidylinositol from the SPE cartridges.

One laboratory noted that the method should specify that the

hydrolysis procedure be performed in a fume hood. Additional

information was added to AOAC Final Action Method

2011.18

to address some of study participants’ comments and concerns

listed above.

Conclusions

AOAC Method

2011.18

was collaboratively studied by

nine to 10 laboratories from five different countries with

a variety of infant and pediatric nutritional matrixes.

The method demonstrated acceptable repeatability and

reproducibility and met the SPIFAN SMPRs for free and free

plus phosphatidylinositol bound myo-inositol in most of the

matrixes analyzed.

Recommendation

Themultilaboratorycollaborative studydatawere summarized

and presented to the AOAC ERP in September 2014. After

reviewing the data, the ERP voted to move AOAC

2011.18

Final Action status, and the method was approved by the AOAC

Official Methods Board as a Final Action Method.

Acknowledgments

The authors would like to thank the following collaborators

and their associates:

Sumalee Purachaka, Mead Johnson Nutritionals, Don

Huaroh, Muang, Chonburi, Thailand

Lillian Chen and Lipika Basumallick, Thermofisher

Scientific, Sunnyvale, CA

Wu Bolong, Test Center of Chinese Academy of Inspection

and Quarantine, Beijing, China

George Lautenschlager and Scott Christiansen, Perrigo

Nutritionals, Georgia, VT

David Ellingson and John Austad, Covance Laboratories,

Madison, WI

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