ANKOM 200 Series - Manual (Page 31)

Operator’s Manual
Rev C 1/14/15
pg. 31
Appendix A – ADF Method
Acid Detergent Fiber in Feeds - Filter Bag Technique (for A200 and A200I)
Definition
This method determines Acid Detergent Fiber, which is the residue remaining after digesting with H
2
SO
4
and CTAB. The fiber residues are
predominantly cellulose and lignin.
Scope
This method is applicable to grains, feeds, forages, and all fiber-bearing material.
Apparatus
1. Analytical Balance—capable of weighing 0.1 mg.
2. Oven—capable of maintaining a temperature of 102 ± 2°C
(ANKOM
RD Dryer, ANKOM Technology).
3. Digestion instrument—capable of performing the digestion at
100 ± 0.5°C and maintaining a pressure of 10-25psi. The
instrument must be capable of creating a similar flow around
each sample to ensure uniformity of extraction (ANKOM
200 with
65rpm agitation, ANKOM Technology).
4. Filter Bags—constructed from chemically inert and heat resistant
filter media, capable of being heat sealed closed and able to
retain 25 micron particles while permitting solution penetration
(F57, ANKOM Technology).
5. Heat sealer—sufficient for sealing the filter bags closed to ensure
complete closure (1915, ANKOM Technology).
6. Desiccant Pouch—collapsible sealable pouch with desiccant
inside that enables the removal of air from around the filter bags
(MoistureStop weigh pouch, ANKOM Technology).
7. Marking pen—solvent and acid resistant (F08, ANKOM
Technology).
Reagents
1. Acid Detergent Solution—Add 20g cetyl trimethylammonium
bromide (CTAB) to 1L 1.00N H
2
SO
4
previously standardized
(premixed chemical solution available from ANKOM). Agitate
and heat to aid solution.
CAUTION1: Sulfuric acid is a strong acid and will cause severe
burns. Protective clothing should be worn when working with
this acid. Always add acid to water and not the reverse.
CAUTION2: CTAB will irritate mucous membranes. A dust
mask and gloves should be worn when handling this chemical.
Sample Preparation
Grind samples in a centrifugal mill with a 2mm screen or cutter type
(Wiley) mill with a 1mm screen. Samples ground finer may have
particle loss from the filter bags and result in low values.
ADF Procedure (see the ADF Analysis section of the Operator’s
Manual for more detail)
1. Use a solvent resistant marker to label the filter bags to be
used in the analysis.
2. Weigh and record the weight of each empty filter bag (W
1
)
and zero the balance. NOTE: Do not pre-dry filter bags. Any
moisture will be accounted for by the blank bag correction.
3. Place 0.45 – 0.50g of prepared sample in up to 23 of the
bags and record the weight (W
2
) of each. Avoid placing the
sample in the upper 4mm of the bag.
4. Include at least one empty bag in the run to determine the
blank bag correction (C
1
).
NOTE: A running average blank bag correction factor (C
1
)
should be used in the calculation of fiber. The inclusion of at
least one blank bag in each run is mainly used as an
indicator of particle loss. A C
1
larger than 1.0000 indicates
that sample particles were lost from filter bags and deposited
on the blank bag during the extraction. Any fiber particle
loss from the filter bags will generate erroneous results. If
particle loss is observed then the grinding method needs to
be evaluated.
5. Using a heat sealer, completely seal each filter bag closed
within 4mm of the top to encapsulate the sample. NOTE:
Use sufficient heat to completely seal the filter bags and
allow enough cool time (2 sec) before removing each bag
from the heat sealer.
6. Pre-extract only samples containing soybean products or
>5% fat: Extract samples by placing 24 bags with samples
into a container with a top. Pour enough acetone into the
container to cover the bags and secure the top.
CAUTION3: Acetone is extremely flammable. Avoid static
electricity and use a fume hood when handling.
Shake the container 10 times and allow bags to soak for 10
minutes. Repeat with fresh acetone. Pour out acetone and
place bags on a wire screen to air-dry.
Exception – Roasted soybean: Due to the processing of
roasted soy a modification to the extraction is required.
Place roasted soy samples into a container with a top. Pour
enough acetone into the container to cover the bags and
secure the top. Shake the container 10 times and pour off the
acetone. Add fresh acetone and allow samples to soak for
twelve hours. After the soak time, pour out the acetone and
place the bags on a wire screen to air-dry.
7. To eliminate sample clumping, spread the sample uniformly
inside the filter bags by shaking and flicking the bags.