AOACSPIFANMethods-2017Awards

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H aselberger & J acobs : J ournal of AOAC I nternational V ol . 99, N o . 6, 2016  1579

laboratory water and mix to ensure complete dissolution. Transfer ~1 mL of each to autosampler vials. Store at –20°C for up to 6 months. (b)  Mobile phase A.— Deliver laboratory water to an acceptable container and sparge with UHP helium for 10 min. Store under ~3–5 psi blanket of helium on the instrument. Expiration is 30 days at room temperature. (c)  Mobile phase B.— Deliver 1000 mL laboratory water to an acceptable container and sparge with UHP helium for 10 min. Add 40 ± 0.1 g of 50% (w/w) NaOH and continue to sparge for 2 additional min. Store under ~3–5 psi blanket of helium on the instrument. Expiration is 30 days at room temperature. (d)  Mobile phase C.— Deliver 1000 mL laboratory water to an acceptable container and sparge with UHP helium for 10 min. Add 40.8 ± 0.1 g sodium acetate trihydrate and continue to sparge for 5 additional min (or until dissolved). Then filter the solution through the membrane filter. Store under ~3–5 psi blanket of helium on the instrument. Expiration is 14 days at room temperature. E. Sample Preparation (a)  Powder sample .—Reconstitution (if needed). Accurately weigh 5.0 ± 0.025 g into a 100 mL plastic beaker [record powder weight (PW)]. Tare and deliver 40 ± 0.2 g laboratory water to beaker [record water weight (WW)]. Allow to stir for 30 min, or until dissolved. (b)  Sample dilution.— Samples require differing dilutions according to their individual fructan content as per Table  2016.06D . For example, a liquid ready-to-drink (RTD) sample containing 0.5% fructan would be diluted at a rate of 7 g to 200 mL. Record all weights to 4 decimal places. This solution can be used also with the quantitative fructan methodology in Part II. This is SW 1 . (c)  Filtration.— After bringing the samples to volume, filter through a 0.45 µm nylon syringe filter into an autosampler vial (prepared samples can be stored in vials at 2–10°C for 5 days). F. Instrumental Analysis (a) Gradient.— Fructans are eluted using a gradient of NaOH and sodium acetate at 1.0 mL/min as per Table 2016.06E . Column and detector compartment are maintained at 20°C. Note: A CarboPac PA1 guard is used for this procedure rather than the borate trap used in Part II for quantitative fructan determination. Therefore, if same day analysis is desired, two separate HPAEC-PAD systems are needed. The gradient program recommended in Table 2016.06E has

Table 2016.06D. Sample size guidelines

Fructan level (as-is), % SW 1

Volumetric flask size, mL a

Sample type

, g

Powder product

0.27–1.0

10 g ± 10%

50

1.1–10

7 g ± 10%

200

11–45

4 g ± 10%

500

RTF product b

0.03–0.20 10 g ± 10%

50

0.21–1.0

7 g ± 10%

200

1.1–5.0

4 g ± 10%

500

Commodity 1000 a  For the sake of procedural simplification, the density of this solution is treated as 1 g/mL, so that the weight of the diluted solution in grams can be assumed equal to the flask volume (in mL). This incurs a <0.3% error, which is inconsequential for a result reported to 3 significant digits. b  For concentrated liquid (CL) products dilute 10 mL of product with 10 mL of laboratory water and then treat the diluted material per RTF guidelines. 45–100 0.4 g ± 10%

C. Reagents (a)  Laboratory water.— ASTM Type 1.

(b)  NaOH solution .—50%, w/w (Fisher Part No. SS254-500 or equivalent). If an alternate vendor is selected, it is imperative that the carbonate level be equivalent to or less than Fisher (≤0.10%). (c)  Sodium acetate trihydrate.— Reagent grade (Sigma Part No. 71188 or equivalent). (d)  Helium gas.— Ultra-high purity (UHP). (e)  Fructan commodities.— For use as retention time (RT) standards . (1) Short-chain Fructooligosaccharides (scFOS, derived from sucrose). —Used to identify GF 3 and GF 4 (which will be the second and third/last major peaks present). This commodity is a representative of a category 1 fructan. Alternately one may use discrete GF 3 and GF 4 reagents (e.g., Wako Part No. 295-73401). (2) Beneo Orafti HP Inulin.— Used to identify category 3 type fructans. D. Preparation of Standards and Solutions (a)  Fructan RT marker standards.— Weigh 0.4 ± 0.004 g of each fructan reference material, scFOS (or ~0.050 g each of individual GF 3 and GF 4 standards) and Beneo Orafti HP. Transfer to a 1000 mL volumetric flask. Bring to volume with

Table 2016.06E. Qualitative ID (Part I) gradient Time, min Flow, mL/min

A (laboratory water), % B (500 mM NaOH), %

C (300 mM NaOAc), % Curve

0

1.0

67.0

8.0

25.0

NA

0

1.0

67.0

8.0

25.0

5

40.0

1.0

0.0

8.0

92.0

5

45.0

1.0

0.0

8.0

92.0

5

45.1

1.0

67.0

8.0

25.0

5

55.0

1.0

67.0

8.0

25.0

5