Hach DR2400 Manual page 401

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Table of Contents

Table 1 Substances that Cause a Negative Interference (continued)

Interfering Substance

* Read the molybdenum concentration immediately after the beep of the 2-minute reaction period.

Interfering Substance

Benzotriazole

Phosphonate HEDP

PBTC (phosphonate)

Molybdenum_PP_Low_TER_Eng_Ody.fm

Greater than 6500 mg/L

Table 2 Substances that Cause a Positive Interference

Greater than 210 mg/L

Greater than 1325 mg/L

Greater than 6 mg/L

Positive interference of about 10% up to 30 mg/L. As the concentration increases above

30 mg/L, a decrease in the molybdenum concentration reading occurs (negative interference).

Greater than 600 mg/L

Table 3 Non-Interfering Substances

Highly buffered samples or extreme sample pH may exceed the buffering

capacity of the reagent and require sample pretreatment. Adjust the sample pH

to between 3–5 by adding, dropwise, an appropriate amount of acid or base such

as 1.0 N Sulfuric Acid Standard Solution (Cat. No. 1270-32), 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 by dividing the total volume

(sample + acid + base) by the original volume and multiplying the test result by

this factor.

After a number of samples have been analyzed, the sample cells may exhibit a

slight blueish discoloration. Rinse the cells with 1:1 Hydrochloric Acid Solution

(Cat. No. 884-49) to eliminate this build-up.

Molybdenum, Molybdate

Interference Levels and Treatments

Highest Concentration Tested

Molybdenum, Molybdate