Hach-Lange DR 5000 brewerie analysis, supplementary software LZV570 - Manual (Page 18)

18
Working procedures
Reagents
• MN polyamide SC 6
• Solution 1: n-butanol/37% hydrochloric acid 5+1 (V/V).
• Solution 2: Dissolve 120 mg iron(II) sulphate (FeSO
4
x 7 H
2
O)
in 100 ml solution 1.
Sample preparation
1. Centrifuge worts and young beers for 10 min at 3000 rpm.
2. Pipette 5 ml beer or wort and 5 ml dist. H
2
O into a 50 ml mixing
cylinder.
3. Pipette 10 ml distilled water (blank value) into a 50 ml mixing
cylinder
4. Use 10 ml dist. water to rinse 0.5 g polyamide powder into
each mixing cylinder.
5. Shake the two mixing cylinders mechanically for 40 min.
6. Filter each suspension through a 1 G4 frit, rinsing twice with
about 20 ml H
2
O.
7. Suction-dry the frits and polyamide powder. Use a spatula to
transfer each residue to a test tube, rinsing the final traces into
each test tube with 15 ml of solution 1.
8. Add 0.5 ml of solution 2 and heat both test tubes for 30 min in
a bath of boiling water (stir well with a glass rod for the first
5 min).
9. Remove the glass rod, rinse with a little of solution 1, bring the
test tubes to 20 °C and make each one up to 25 ml with
solution 1.
10. Measure the absorbance of the solution in a 10 mm rectangular
cuvette at 550 nm against a similarly treated blank value
solution (10 ml dist. water instead of beer).
Results
The result is expressed in mg/l, without decimal places.
Accuracy
r = 9
Standard values
50–70 mg/l depending on the raw materials and technical
measures; correspondingly lower after stabilisation with PVPP.
Literature
MEBAK Brautechnische Analysenmethoden
4th Edition 2002 Volume II, pp 109ff