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    Home > Chemicals Industry > Chemical Technology > Solid waste. Determination of lead, zinc and cadmium. Flame atomic absorption spectrophotometry (3)

    Solid waste. Determination of lead, zinc and cadmium. Flame atomic absorption spectrophotometry (3)

    • Last Update: 2022-03-09
    • Source: Internet
    • Author: User
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    (6) Operation steps

    1.


    Different types of flame atomic absorption spectrophotometers have different optimal measurement conditions, and the test conditions can be optimized according to the requirements of the instrument manual


    Table 5-13 Reference measurement conditions of the instrument


    2.


    (1) Lead standard curve series


    Pipette 0.


    (2) Zinc standard curve series


    Accurately pipette 0.


    (3) Cadmium standard curve series


    Accurately pipette 0.


    3.


    The prepared blank sample is measured under the same conditions as the establishment of the calibration curve


    4.


    The prepared sample is measured under the same conditions as the establishment of the calibration curve


    (7) Calculation and expression of results

    1.


    The content w (mg/kg) of the element to be tested in the solid or dry semi-solid solid waste is calculated according to formula (5):


    The content w (mg/kg) of the element to be tested in the liquid or semi-solid solid waste that does not need to be dried is calculated according to formula (6):

    Where P 1 -the mass concentration of the elements in the sample obtained from the calibration curve, mg/L;

    P 0 —The mass concentration of elements in the laboratory blank sample, mg/L;

    V—Sampling volume when the solid waste leachate is digested, mL;

    V 0 —The constant volume of the sample after digestion, mL;

    m 1 —The weighed amount of solid waste sample before drying, g;

    m 2 —the mass of the solid waste sample after drying, g;

    m 3 —the weighed amount of the sample after grinding and sieving or the sampling amount of liquid solid waste, g
    .

    2.
    Result presentation

    For solid waste, when the measurement result is less than 100mg/kg, one decimal place is retained; when the measurement result is greater than or equal to 100mg/kg, three significant digits are retained
    .

    For solid waste leachate, when the measurement result is less than 1.
    00mg/L, keep two decimal places; when the measurement result is greater than or equal to 1.
    00mg/L, keep three significant digits
    .

    (8) Interference elimination

    (1) When the calcium content is higher than 1000mg/L, the absorption of cadmium is inhibited; when the calcium content is 2000mg/L, the signal is inhibited by 19%
    .
    When the iron content exceeds 100mg/L, the absorption of zinc is inhibited, and the interference of coexisting components can be eliminated by adding lanthanum nitrate
    .
    When the salt content in the sample is very high and the wavelength of the analysis spectrum is lower than 350nm, non-characteristic absorption occurs.
    For example, the background absorption caused by high-quality calcium concentration makes the measurement result of lead higher
    .

    (2) When the sample matrix composition is complex or unknown, or the standard addition recovery rate exceeds the quality control requirements of this method, the standard addition method should be used to determine the sample and calculate the result
    .
    For the standard addition method, please refer to this section.
    Determination of Lead and Cadmium in Solid Wastes.
    Graphite Furnace Atomic Absorption Spectrophotometry-Interference Elimination
    .

    (9) Quality assurance and quality control

    (1) Make at least 2 laboratory blanks for each batch of samples, and the measurement results should be lower than the detection limit of the method
    .

    (2) A calibration curve should be drawn for each analysis, and the correlation coefficient should be greater than 0.
    999
    .
    Otherwise, the calibration curve needs to be redrawn
    .

    (3) Every 10 samples should be analyzed for an intermediate mass concentration point of the calibration curve, and the relative deviation of the measurement result from the mass concentration of the calibration curve should be less than 10%
    .
    Otherwise, the calibration curve needs to be redrawn
    .

    (4) The zero point calibration of the instrument should be performed every 20 samples analyzed
    .

    (5) Each batch of samples should be tested in parallel at least at a ratio of 10%.
    When the number of samples is less than 10, at least one parallel double sample should be tested, and the relative deviation of the two determination results should be less than 20%
    .

    (6) At least 10% standard addition recovery test should be done for each batch of samples.
    If the number of samples is less than 10, at least one should be done.
    The standard addition recovery rate should be 80%~120%
    .

    (7) When measuring samples in batches, every 10 samples are a group, and a quality control sample of the element to be measured is added to check the drift degree of the instrument
    .
    When the measured value of the quality control sample exceeds the allowable range, the instrument needs to be re-adjusted with a standard solution before continuing the measurement
    .

    (10) Matters needing attention

    (1) The crucibles and glass containers used in the experiment must be soaked in nitric acid solution for more than 12 hours, rinsed with tap water and experiment water in turn, and placed in a clean environment to dry
    .
    For newly used or suspected contaminated containers, they should be immersed in hot hydrochloric acid solution (the temperature is higher than 80℃ and lower than the boiling temperature) for at least 2h, and then immersed in hot nitric acid solution for at least 2h, and rinsed with tap water and experimental water in turn.
    Dry in a clean environment
    .

    (2) When the sample solution is heated to near dryness, the temperature should not be too high to avoid splashing
    .

    (3) Waste liquids and wastes generated during the experiment should be collected separately and entrusted to a qualified unit for disposal
    .

     

     

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