AOAC OMB Final Action Recommendation (December 2019)-2016.14

2016.14 (October 2019) – FOS-03 METHOD

FOR ERP USE ONLY DO NOT DISTRIBUTE

(d) Post-column addition reagent, sodium hydroxide solution (300 mM).— Into an eluent bottle,

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introduce 985 mL water C(a) and add (using a single-use plastic pipette) 15.6 mL of 50 % (w/w)

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NaOH solution C(j) . Swirl the solution gently to mix and degas for 20 min. Stable for 1 month at

199

200

room temperature, degas on day of use.

G.

Preparation of Standards

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Using volumetric flasks, prepare a 6-level standard curve by diluting the glucose stock solution D(e) and 202 the fructose stock solution D(f) made up to the final volume with water C(a), as described in Table 203 2016.14B . 204 Treat each of the 6 standard solutions as follows: Into a 1.5-mL microtube, transfer 200 µL of standard 205 solution, 200 µL of water C(a) and 100 µL of N,N’- diacetylchitobiose internal standard solution D(d) (use 206 same N,N’-diacetylchitobiose solution for standards and samples), mix well (vortex). Then transfer 400 µL 207 of this solution to a 2-mL microtube, add 1200 µL of SPE elute solution D(n) and mix well (vortex). To 208 700 µL of this solution, add 300 µL of sodium acetate buffer D(c) . Mix well (vortex) and centrifuge at 209 10 000 × g for 5 min. Transfer 900 µL of the supernatant into a vial suitable for the instrument 210

211

autosampler.

Table 2016.14B. Dilution scheme for the preparation of the standard curve 212

Volume of fructose stock solution, µL

Volume of glucose stock solution, µL

Fructose concentration, µg/mL

Glucose concentration, µg/mL

Final volume, mL

Standard

Level 1 Level 2 Level 3 Level 4 Level 5 Level 6

200 400 800

40

100

20

2

200 400 600 800

20 20 20 20 20

200 400 600 800

50

100 150 200 250

1200 1600 2000

1000

1000

10