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1582
H
aselberger
&
J
acobs
:
J
ournal of
AOAC I
nternational
V
ol
. 99, N
o
. 6, 2016
(c)
Working standards (WS).—
Dilute fructose stock and
glucoheptose IS solution with laboratory water, using class
A glass pipets for transfer of fructose and IS solutions to
appropriate volumetric flasks for final dilution, as follows:
(1)
WS1
.—5 mL Fructose stock, 10 mL IS solution to 200 mL final
volume.
(2) WS2
.—5 mL Fructose stock, 5 mL IS solution to 100 mL
final volume.
(3) WS3
.—25 mL Fructose stock, 5 mL IS solution to
100 mL final volume
(4) WS4
.—50 mL Fructose stock, 5 mL IS solution to
100 mL final volume.
Store frozen at –20°C for up to 6 months.
(d)
Acetic acid solution 0.2 M
.—Transfer 2.9 mL acetic acid
to a 250 mL flask containing ~100 mL laboratory water. Dilute
to volume with laboratory water and mix by inversion. Transfer
to a suitable container for storage up to 2 years.
(e)
50 mM NaOH solution.—
Transfer 5 mL of 1 M NaOH
into a 100 mL flask containing ~50 mL laboratory water. Bring
to volume with laboratory water mix thoroughly. Store in
suitable plastic container for up to 2 years.
(f)
Alkaline borohydride solution ~10 mg/mL.—
Immediately
before use, weigh 100 mg sodium borohydride into a 15 mL
tube. Dissolve in 5 mL of 50 mM NaOH (this is enough for
24 samples). Use for up to 4 h after addition of hydroxide.
(g)
Sodium maleate buffer 0.1 M, pH 6.5.—
Weigh 2.9 ± 1%
of maleic acid in a 250 mL beaker. Dissolve in ~150 mL
laboratory water. Adjust pH to 6.5 with 1 M NaOH. Transfer to
250 mL flask; bring to volume with laboratory water and mix
thoroughly.
(h)
Sucrase solution (~30 units/mL).
—Measure 10 mL
maleate buffer in a graduated cylinder. Deliver to sucrase vial.
Cap and swirl gently to dissolve. Divide into ~450 µL aliquots
and store frozen at –20°C (each tube is enough for two samples)
for up to a year.
(i)
Acetate buffer.—
Combine 2.9 mL glacial acetic acid with
450 mL laboratory water. Adjust pH to 4.5 with 1 M NaOH.
Bring total volume to 500 mL with laboratory water and mix
thoroughly.
(j)
Fructanase solution (~909 units/mL).—
Dissolve contents
of fructanase vial in 22 mL acetate buffer. Swirl gently to
dissolve. Divide into ~1 mL aliquots and store frozen at –20°C
for up to a year (each tube should contain enough for nine
samples).
(k)
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.
(l)
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.
(m)
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.
K.
Sample Preparation
If running in parallel with Part I, above, an aliquot from the
diluted solution,
E(b)
, can be used in this method. If so skip to
step
(c)
, below. Otherwise proceed to step
(a)
, below
(a)
Powder sample reconstitution (if sample is RTF, skip
this step).—
Accurately weight 5.0 ± 0.025 g into a 100 mL
plastic beaker and record weight. This is PW. Tare and deliver
40 ± 0.2 g laboratory water to beaker. Record water weight. This
Table 2016.06G. Quantitative fructan determination (Part II) gradient
Time, min
Flow, mL/min
A (lab water), %
B (500 mM NaOH), %
C (300 mM NaOAc), %
Curve
0
1.0
90.0
10.0
0.0
NA
0
1.0
90.0
10.0
0.0
5
20.0
1.0
90.0
10.0
0.0
5
20.1
1.0
0.0
80.0
20.0
5
30.0
1.0
0.0
80.0
20.0
5
30.1
1.0
90.0
10.0
0.0
5
45.0
1.0
90.0
10.0
0.0
5
Table 2016.06H. Column cleaning/trap regeneration gradient
Time, min
Flow, mL/min
A (Lab water), %
B (500 mM NaOH), %
C (300 mM NaOAc), %
Curve
0
1.0
60.0
40.0
0.0
NA
0
1.0
60.0
40.0
0.0
5
15.0
1.0
60.0
40.0
0.0
5
15.1
1.0
0.0
40.0
60.0
5
30.0
1.0
0.0
40.0
60.0
5
30.1
1.0
60.0
40.0
0.0
5
45.0
1.0
60.0
40.0
0.0
5
27