AOAC SPIFAN Nutrients ERP-Final Review (Oct. 2018)

B handari et al . : J ournal of AOAC I nternational V ol . 101, N o . x , 2018  11

Table 3. Summary of the precision of the method for total folate analysis in the SPIFAN MLT samples a

Overall mean of all data (grand mean)

Total No. of labs

Total No. of replicates

RSD r

RSD R

HorRat

Sample No.

MLT samples

Sum [ n (L)]

μg/100 g

% % HorRat

P

1 2 3 4 5 6 7 8 9

Milk-based infant formula

11 10 11 11 10 11 11 11 11 11 11

22 20 22 33 30 22 22 22 22 22 22

154.8 131.5 173.7 245.3 171.7 323.5

5.3 4.2 6.6 6.1 5.9 4.7 3.7 5.0 4.1 5.5 3.5

10.0 12.1 15.7 10.1 10.3 10.2 11.0 15.7

0.66 0.79 1.06 0.72 0.70 0.76 0.62 0.74 0.68 0.88 0.61

Infant formula powder, partially hydrolyzed milk-based Infant formula powder, partially hydrolyzed soy-based NISR SRM 1869 Infant/Adult Nutritional Formula

Soy-based infant formula

Low-fat adult nutritional powder

Adult nutritional RTF high-protein liquid Infant formula RTF, milk-based liquid Child formula powder – milk-based

48.9 15.6

349.5 258.6

9.0

10 11

Infant elemental powder

12.2 10.6

Adult nutritional RTF high-fat liquid

57.0

Specifications Specifications

0.5–21.5

≤11% ≤32% 0.5–2.0 ≤7% ≤16% 0.5–2.0

AOAC SMPR 2011.006 Requirements/Satisfactory Performance

>21.5

a  Results of total folate reported as folic acid, mcg/100 g.

Table 4. The method accuracy evaluation: Folic acid results in the NIST SRM 1869 infant formula adult nutritional in comparison with the consensus value

NIST SRM 1869

Parameters

Symbol

Units

Sample 4

Total number of laboratories Total number of replicates

11 33

P

n

Overall mean of all data (grand mean) Repeatability standard deviation Reproducibility standard deviation Repeatability relative standard deviation Reproducibility relative standard deviation

Mean

μg/100 g μg/100 g μg/100 g

211.1

SD r SD R

14.3 23.5

RSD r RSD R

% %

6.8

11.1 0.78

HorRat value

HorRat R

NIST consensus value a

Mean

μg/100 g μg/100 g

215.0

NIST consensus range a , minimum = mean - (1 × SD); maximum = mean + (1 × SD)

Minimum–maximum

201–229

a  Preliminary results based on documentation through an interlaboratory study with participation of 17 laboratories.

and adult nutritionals. The folate SMPR ( 2011.006 ), as well as the MLT protocols for the method, did not expect reporting of amount of the vitamers (folic acid, 5-CH3-THF, and 5-CHO- THF) in the SPIFAN Folate MLT samples. The precision of their analysis by the method were not required for evaluation of the method performance, but the method is capable of analyzing the relevant folate vitamers. SPIFAN, while recommending the method to advance to FinalAction status in September 2017, also requested that the study director provide results of individual relevant folate vitamers in the report if possible. The results of the concentration of individual folate vitamers (μg/100 g) were calculated in all of the MLT samples and are presented in Tables 5–7. The results were subjected to the statistical analysis using the AOAC protocols (19). Two sets of outliers were identified and excluded as Cochran outliers in calculation of average and precision values for folic acid analysis (Table 5). The outliers excluded for folic acid precision evaluation were for the same samples and labs as earlier identified for total folate analysis.

One of the outliers was the result for the partially hydrolyzed milk-based infant formula powder (Sample 2) from laboratory 7, and the other one was the soy-based infant formula sample (Sample 5) from laboratory 8 (Table 5). No other outliers were identified, and all other results were used in the generation of averages and precision values for folic acid (Table 5). No outliers were identified or excluded in the calculation of averages and precision values for all of the samples for 5-CH3-THF as well as 5-CHO-THF. All results were used in the generation of precision and averages of these vitamers. The results for 5-CH3-THF are presented in Table 6 and 5-CHO-THF in Table 7. Folic acid concentration in liquid RTF samples ranged from 14 to 57 μg/100 g, whereas in the powder samples, it ranged from 129 to 315 μg/100 g. The folic acid RSD r was found to be in the range of 3.2 to 6.8% and RSD R in the range of 9.5 to 15.1%. The sample with folic concentration less than 21.5 μg/100 g was found to have RSD r of 5.1% and RSD R