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QUATERNARY AMMONIUM COMPOUNDS, continued
c) Analyze 25 mL of the 5 mg/L CTAB standard solution according to
the preceding procedure. The result should be 5.0 ±0.1 mg/L.
Standard Additions Method
a) Use a TenSette Pipet to add 0.5, 1.0 and 1.5 mL of Q.A.C. Standard
Solution, 100 mg/L as CTAB, to three 50-mL samples. Mix thoroughly.
b) Analyze 25 mL each sample according to the above procedure. The
QAC concentration should increase by 1.0 mg/L CTAB for each 0.5 mL
addition of standard.
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%.
Constituent
Positive Interferences:
Calcium (as CaCO
Chlorine, HOCl and OCl
Igepal nonionic surfactant
-
Iodine, I
3
3+
Iron, Fe
Liquimine 14-P, filming amine
Magnesium, Mg
Sodium polyphosphate
Tribenzylamine
Triton X-100 nonionic surfactant
Urea
Negative Interferences:
Cyanuric acid
Niaproof anionic surfactant
Polyacrylic acid
Sodium lauryl sulfate
No Interferences:
Potassium alum, AlKS
Silica, H
SiO
2
Sodium thiosulfate, Na
)
3
-
2+
O
2
8
3
S
O
2
2
3
57-36
Level Above Which
Constituent Interferes (mg/L)
1,350
7
3
3
80
1,825
1,350
1,325
7
4
8
70
11
16
8
Highest Concentration
Tested (mg/L)
500
400
30
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