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    Determination of heavy metals in organic chemical products. Visual colorimetric method

    • Last Update: 2022-01-19
    • Source: Internet
    • Author: User
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    1 Scope

    This standard specifies the test method for the determination of heavy metals in organic chemical products by visual colorimetry
    .

    The wood standard is suitable for samples with heavy metal content (calculated as Pb) of 0.
    1ug/mL~4.
    0ug/mL

    .

    2 Normative references

    The clauses in the following documents have become clauses of this standard after being quoted in this standard
    .
    For dated reference documents, all subsequent amendments (excluding errata content) or revisions do not apply to this standard.
    However, all parties that have reached an agreement based on the wooden standard are encouraged to study the latest version of the documents that can be used.
    Version.
    For undated reference documents, the latest version is applicable to this standard

    .

    Preparation of GB/T602-2002 Standard Solution for Determination of Impurities in Chemical Reagents

    Preparation of preparations and products used in GB/T603-2002 chemical reagent test method

    GB/T6682-1992 Analytical laboratory water specifications and test methods (neqISO3696: 1987)

    3 Principle

    In a weakly acidic solution, the heavy metals copper, lead, and mercury are plasma-precipitated into corresponding sulfides with a saturated aqueous solution of hydrogen sulfide, and the color produced is compared with the standard color by visual method
    .

    4 Warning

    Some test procedures specified in the test method may lead to dangerous situations, and the operator should take appropriate safety and protective measures
    .

    5 Reagents

    Unless otherwise specified, only reagents confirmed to be analytically pure and grade 3 water specified in GB/T6682-1992 are used in the analysis
    .

    The standard solutions, preparations and products used in the analysis for impurity determination shall be prepared in accordance with the provisions of GB/T602-2002 and GB/T603-2002 when other requirements are not specified
    .

    5.
    1
    Acetic acid solution: 3+7;

    5.
    2
    Ammonia solution;

    5.
    3 Hydrochloric acid solution;

    5.
    4 Saturated hydrogen sulfide water;

    5.
    5 Lead standard solution: 0.
    01mg/mL; accurately draw 10mL of the standard solution for lead impurity determination (0.
    1mg/mL) in a 100mL volumetric flask, dilute to the mark, and shake well

    .
    Prepare fresh before use.

    6 Instruments

    General laboratory equipment and two matching 50mL colorimetric tubes
    .

    7 Analysis steps

    7.
    1 Process the sampling well according to the method specified in the product standard.
    If the processed sample is a solution, transfer a certain amount of solution to a 50mL colorimetric tube, and add 0.
    2mL acetic acid solution: if the processed sample is a residue , Can be dissolved with 0.
    2mL acetic acid solution first, and transferred quantitatively into the colorimetric tube (should ensure that the pH of the solution is about 4, if necessary, it can be adjusted with aqueous ammonia or hydrochloric acid solution)

    .
    Add 10 mL of saturated
    hydrogen sulfide water, dilute to the mark with water, and shake well to make the sample solution
    .

    7.
    2 The standard colorimetric solution is to take the prescribed amount of lead standard colorimetric solution and the sample solution at the same time according to the specification value of the product standard

    .

    7.
    3 In the absence of direct sunlight, observe axially or laterally within 10 minutes, and compare with the standard colorimetric solution

    .

    8 Results presentation

    The color of the sample solution is not deeper than that of the standard colorimetric solution, and the heavy metal content (in terms of Pb) in the sample is qualified
    .

    Related Links: Determination of Ignition Residues of Organic Chemical Products

     

     

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