Hach-Lange LZV936 - DR 6000 Brewery Analysis software Benutzerhandbuch
Seite 39
English 39
Procedure for photometric iodine sample
1.
Prepare the blank value (phosphate buffer), the iodine blank value
and the samples in accordance with the work procedure.
2.
Select STORED PROGRAMS > SELECT BY NUMBER.
3.
Enter the number 2010 for the program "Photometric iodine
sample". Confirm with OK.
4.
Press START to start the program.
5.
Enter the blank value (phosphate buffer) and press ZERO.
Z1 is shown on the display.
6.
Insert the iodine blank value cuvette (see sample preparation) and
press READ.
R1 is shown on the display.
7.
Insert the analysis cuvette with the prepared sample and press
READ.
R2 is shown on the display.
8.
Remove the analysis cuvette and dispense 0.5 mL 0.02N iodine
solution into the analysis cuvette.
9.
Mix the content immediately with the "spatula" and insert the
analysis cuvette after 30 sec. Press READ.
The result is shown on the display.
Note: In order to analyze further samples, repeat the procedure
from step 7. The prepared iodine blank value solution can be used
for the complete measurement series.
Thiobarbituric acid number (TAN)
The thiobarbituric acid number applies as the summary variable for the
thermal load of malt and wort. It is an indicator that in addition to 5-
hydroxymethylfurfural (HMF) records a multitude of products of the
Maillard reaction and other organic compounds.
Principle
The examination sample is used with acetic thiobarbituric acid solution
in reaction and the resulting yellow coloration is measured
spectrophotometrically.
Application area
Beer, wort, congress wort or malt extract
Measurement range
0–100
Accessories
•
Water bath, 70 °C (158 °F)
•
Brown reaction flasks with ground-in stopper, 20 mL or 25 mL
•
Spectrophotometer, 448 nm
•
10 mm rectangular cuvette OS
Reagents
•
Acetic acid, 90 %:
dilute 225 g acetic acid 100 % (glacial acetic acid) with dist. H
2
O to
250 g.
•
Thiobarbituric acid, 0.02 mol/L: Dissolve
0.288 g 2-thiobarbituric acid (M = 144.15 g/mol) in 100 mL
volumetric flask with 90 % acetic acid by warming in the water bath
and after cooling to 20 °C (68 °F) fill up to the mark with 90 % acetic
acid. Prepare fresh daily.
•
Diatomaceous Earth
Sample preparation
Note: Follow procedure carefully as accuracy can affect final results.
1.
Clear cloudy examination solutions through filtration over
diatomaceous earth.