Zinc

Method (adapted from APHA Standard Method 3500-Zn B. Zincon Method)

Zinc forms a blue complex with zincon in a solution buffered to pH 9.0. Cyanide is added to complex zinc and heavy metals. Cyclohexanone is added to free zinc selectively from its cyanide complex so that it can be complexed with zincon to form a blue color. Sodium ascorbate reduces manganese interference.

  • To 20 mL of sample add the following reagents in this order with mixing between each step
            - 0.5 g sodium ascorbate
            - 5 mL buffer solution, pH 9
            - 2 mL potassium cyanide solution, 1%
            - 3 mL zincon solution
    1. Pipette 20 mL of this solution to a clean 50 mL flask
    2. Reserve the remaining solution to zero the instrument
    3. Add 1 mL cyclohexanone to the flask. Swirl for 10 seconds. 
    4. Use solution without cyclohexanone to zero the instrument
    5. Read absorbance of solution with cyclohexanone after 1 minute.


    Reagents


     

     Vendor

     Catalog #

     Cost

     Shelf life

    Zinc reagent set, zincon OR
    Zinc test kit
    Hach OR
    Hanna
    2429300 OR
    HI 3854
    $56.35 for 100 tests OR
    $43.99 for 100 tests
     
    Zinc standard, 1 mL = 1 mg ZnLabchemLC134007$17.90 for 125 mL 36 months
    Ċ
    Joanne Long,
    Mar 26, 2013, 3:25 PM
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