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Table 8. Digestion Guidelines for Specific Sample Types
Sample Sample Amount Preheat Amount of Special
Type Weight of Acid Time Peroxide Instructions
Plant 0.25 to 5 g 4 mL 4 min. 10 mL Use N-free paper
Tissue to weigh sample
Meat & 0.5 g or 4 mL or as 4 min. 10 mL May use
Poultry predigestion in predigest predigestion
procedure; see
Systems for Food,
Feed and
Beverage Analysis
(Lit. Code 3120.)
Fluid 0.1 to 0.25 g 4 mL 4 min. 10 mL Add 0.4 g Kjeldahl
Fertilizers Reduction Powder
to flask before
adding sulfuric
acid. Place the
flask in an 80 °C
oven 15 minutes
before digestion.
Use N-free paper to
weigh sample
Feed & 0.25 g 4 mL 4 min. 10 mL Use N-free
Forage paper to weigh
sample
Dairy 0.25 to 2.0 g 4 mL 4 min. 10 mL Use N-free paper
to weigh dry
samples (cheese)
Cereal 0.25 to 0.5 g 4 mL 4 min. 10 mL Use N-free paper to
weigh sample
Beverage approx. 5 g 4 mL 1 min. 10 mL Preheat acid for 1
(pipet into minute then add
funnel) sample through
funnel. Heat flask
30 seconds after
sample is in flask.
Sludge < 2.5 g wet 4 mL 3 to 10 mL or Heat the diluted
sludge 5 min. increase in digest for 15
< 0.5 g dried 5 mL minutes and filter.
sludge increments
Water & not more than 3 mL until acid 10 mL or Water must
Waste- 0.5 g solid is refluxing increase in evaporate before
water (mL = 50/C; 5 mL acid will reflux.
C = % solids) increments Boiling chips
required.
Bath 0.3 to 10 mL 4 mL 4 minutes 10 mL Water must
Solutions evaporate before
acid will reflux.
Boiling chips
required.
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