6. AOACSPIFANMethods-2018Awards

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1398  Jing et al. : J ournal of AOAC I nternational Vol. 98, No. 5, 2015

Table 2014.04E. Mass spectrometer (Xevo TQ-S) operating conditions Ionization mode ESI positive Capillary voltage, kV 2.0 Collision gas pressure, mtorr 2–5 × 10 –3 Source temperature, ° C 150 Source offset, V 30 Desolvation temperature, ° C 550 Cone gas flow, L/h 300 Desolvation flow rate, L/h 1000 Peak width half-height, amu a 0.7 a Instrumental resolution parameters for the TQ-S are set up by IntelliStart to achieve a resolution of approximately 0.7 amu across the mass range. Table 2014.04F. Chromatographic parameters Mobile phase A 10 mM ammonium acetate [water–acetonitrile (95 + 5, v/v)] Mobile phase B 10 mM ammonium acetate [water–acetonitrile (5 + 95, v/v)] Flow rate 0.7 mL/min (analytical) Flow rate into MS Full flow Column Acquity UPLC BEH HILIC 1.7 µm, 2.1 × 100 mm Column temperature, 25 Injection volume, µL 10 Injection type Full loop Sample temperature, ° C 8

Table 1. Method performance requirements Choline (a)

Carnitine (b)

Analytical range

2–250

0.16–20

NA a

LOD LOQ

0.7 2.0

≤0.16

Repeatability (RSD r )

10% at 2 mg/100 g; otherwise 5% 90–110% at all levels over range 15% at 2 mg/100 g; otherwise 10% (a) mg/100 g concen- trations apply to: ( 1 ) “ready-to-feed” liquids “as is”; ( 2 ) reconsti- tuted powders (25 g into 200 g water); and ( 3 ) liquid concentrates diluted 1:1 by weight. For all concentra- tions, choline will be expressed as mg/100 g reconstituted liquids. Report as total choline.

≤8%

Recovery

90–110% at all levels over range

Reproducibility (RSD R )

≤15%

(b) mg/100 g concen- trations apply to: ( 1 ) “ready-to-feed” liquids “as is”; ( 2 ) reconsti- tuted powders (25 g into 200 g water); and (3) liquid concentrates diluted 1:1 by weight.

a NA = Not applicable.

Table 2. SLV test materials

Sample size used for repeatability SLV, g

Product type

Code

5.0 a 4.3 a 3.7 a 3.9 a 4.1 a 4.1 a

NA c

SRM 1849a

Infant powder milk

D04HTCVV

Infant powder soy

E29JVLV

Infant powder milk part hydrolyzed 1172572116

Infant powder soy part hydrolyzed 117257651Z

Table 2014.04G. Gradient profile

Adult powder low fat

00394RF00

Mobile phase

7.5 a,b

Time, min Flow, mL/min

A, %

B, % Curve

Adult powder milk

11750017V3

2.7 a 3.7 a

Initial 0.10 6.00 6.01 8.00 10.00 13.00 13.20 15.00

0.7 0.7 0.7 0.7 0.7 1.0 1.0 0.7 0.7

8.0 8.0

92.0 92.0

Child formula powder

00412RF00

6 6 6 6 6 6 6 6

Infant elemental powder

00403RF00

22

78

3.0

Infant RTF milk

SPIFAN CTL

100 100

0 0

0.8

Adult RTF high protein

00414RF00 00406RF00

Adult RTF high fat 0.6 a  Aliquot size from an 11.1% (w/w) reconstitution in water (25 g powder plus 200 g water). b  An abnormally large sample size was needed for this sample, in which both choline and carnitine were present at

8.0 8.0 8.0 8.0

92.0 92.0 92.0 92.0

when stored in a refrigerated (8°C) autosampler. Filtered samples (aqueous) and WS are stable for 7 days stored at 2–8°C. ( d ) The method can also determine free choline and free carnitine by bypassing the microwave digestion and basic hydrolysis. Simply dilute the same sample size with water, add 125 µL of MIX-IS, and dilute to 10 mL in a tube. Mix, and then dilute this solution 1 mL to 25 mL with water in another tube. Mix, filter approximately 1 mL of sample slurry, and then dilute

10x with acetonitrile as above. No nitric acid or ammonia is used.

G. Instrument Operating Conditions

( a )  MS conditions.—See Tables 2014.04D and E . ( b )  UPLC conditions. – See Tables 2014.04F and G .

( c )  UPLC analysis .—Column stability was improved by storing the column in water–acetonitrile (5 + 95, v/v) without