Hach DR2400 - Page 696

Quaternary Ammonium Compounds
Quaternary Ammonium Compounds
Page 2 of 4
QuaternaryAmmCom_PP_Other_DBC_Eng_Ody.fm
Interferences
Interference studies were conducted by preparing a CTAB standard solution of
approximately 3 mg/L as well as a solution of the potential interference.
The constituent was said to interfere when the resulting concentration
changed by 10%.
After several samples have been analyzed, the sample cells may exhibit a
build-up of a pink or purple color. A rinse with 1.0 N Sodium Hydroxide
Solution (Cat. No. 1045-53) followed by a Alconox™ detergent
(Cat. No. 20880-00) wash and deionized water rinse will eliminate the
build-up when it occurs.
Interfering Substance Interference Levels and Treatments
Calcium (as CaCO
3
) Positive interference above 1350 mg/L
Chlorine, HOCl and OCl
–
Positive interference above 7 mg/L
Cyanuric acid Negative interference above 70 mg/L
Igepal™ nonionic surfactant Positive interference above 3 mg/L
Iodine, I
3
–
Positive interference above 3 mg/L
Iron, Fe
3+
Positive interference above 80 mg/L
Liquimine™ 14–P,
filming amine
Positive interference above 1825 mg/L
Magnesium, Mg
2+
Positive interference above 1350 mg/L
Niaproof™ anionic surfactant Negative interference above 11 mg/L
Polyacrylic acid Negative interference above 16 mg/L
Sodium lauryl sulfate Negative interference above 8 mg/L
Sodium polyphosphate Positive interference above 1325 mg/L
Tribenzylamine Positive interference above 7 mg/L
Triton X-100™ nonionic
surfactant
Positive interference above 4 mg/L
Urea Positive interference above 8 mg/L
Highly buffered samples or
extreme sample pH
May exceed the buffering capacity of the reagents and require sample pretreatment. Adjust the
sample pH between 3 and 5 by using a pH meter or pH paper and adding dropwise an
appropriate amount of acid or base such as 1.0 N Sulfuric Acid Standard Solution
(Cat. No. 1270-26) or 1.0 N Sodium Hydroxide Standard Solution (Cat. No. 1045-32).
If significant volumes of acid or base are used, a volume correction should be made.
See Section 3.1.3 Correcting for Volume Additions on page 29.
Non-interfering Substance Highest Concentration Tested (mg/L)
Silica, SiO
2
400
Potassium alum, AlKS
2
O
8
500
Sodium thiosulfate, Na
2
S
2
O
3
30