Hach DR/700 Procedures Manual page 671

TANNIN AND LIGNIN,
STATISTICAL EVALUATION
A single operator repetitively tested samples of two prepared solutions,
using one DR/700, matched sample cells and two representative lots of
testing reagents. Testing 6.0 mg/L tannic acid concentration samples,
the standard deviation was ±0.042 mg/L tannic acid.
Testing zero concentration samples, the limit of detection was 0.031 mg/L
tannic acid. The limit of detection was calculated as three times the
standard deviation when testing zero concentration samples (adapted from
Analytical Chemistry, 1980, 52, 2242-2249).
INTERFERENCES
Sulfite interference can be removed by adding 1 mL of formaldehyde to
the sample before running the test.
Ferrous iron causes a positive interference. Two mg/L of ferrous iron
produce a color equivalent to about 1 mg/L of tannic acid. Add one 0.2-g
scoop of sodium pyrophosphate to the sample before running the test to
eliminate interference due to levels up to 20 mg/L of ferrous iron.
SUMMARY OF METHOD
This test method registers all hydroxylated aromatic compounds,
including tannin, lignin, phenol and cresol. The tyrosine method
produces a blue color proportional to the amount of these compounds
present. The results are reported as total tannin and lignin present
expressed as mg/L tannic acid.
REQUIRED REAGENTS
Tannin and Lignin Reagent Set (up to 100 tests) . . . . . . . . . . . 22446-00
Includes: (1) 675-49, (1) 2560-42
Description
Sodium Chromate Solution
for Tannin-Lignin . . . . . . . . 10 mL . . . . . 500 mL . . . . . . . . . 675-49
TanniVer 3
Tannin-Lignin Reagent. . . . 1 mL . . . . . . 100 mL . . . . . . . . 2560-42
Water, demineralized . . . . . . . . 25 mL . . . . . 4 L . . . . . . . . . . . . . 272-56
continued
Quantity
Per Test Unit
69-11
Cat. No.
Cat. No.