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    Home > Chemicals Industry > Chemical Technology > Solid waste leachate-determination of organochlorine pesticides-gas chromatography (2)

    Solid waste leachate-determination of organochlorine pesticides-gas chromatography (2)

    • Last Update: 2022-03-10
    • Source: Internet
    • Author: User
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    Six, analysis and testing

    (1) Reference conditions of gas chromatography (for reference only, can be adjusted appropriately according to the actual instrument)

    Inlet temperature: 250%:, sampling method: split injection, split ratio is 10:1, constant pressure control, injection volume is 1uL
    .

    ECD detector temperature: 300℃, makeup: 30mL/min
    .

    The chromatographic column connected to the forward inlet is an auxiliary qualitative chromatographic column, and the other conditions of the qualitative analysis are the same as those of the forward inlet analysis
    .

    (2) Calibration curve

    Prepare a standard series of more than 5 points (such as 5.
    00ug/L, 10.
    0ug/L, 50.
    0ug/L, 150uL/L, 200ug/L) that meets the instrument's detection limit, linear range and actual sample mass concentration, diluted with n-hexane Quantification with external standard method

    .

    Draw a standard curve with the peak area of ​​the component as the ordinate and the mass decay concentration of the component as the abscissa
    .
    The retention time of the compound obtained under the conditions of the reference instrument on the HP-5 column is shown in Table 3-1

    .

    Table 3-1 Retention time

    7.
    Result calculation

    (1) Qualitative target compound

    Qualitatively based on the retention time of each component of the standard material
    .
    If you have any questions about the results, you can use a medium-polarity column or a gas chromatography-mass spectrometer to further qualitatively determine

    .

    (2) Quantitative calculation

    The target compound is quantified by an external standard method, and the mass concentration of the target compound in the leachate ρ (uL/L) is calculated according to formula (1)
    .

    ρ=ρ x ×(V x /V i ) (1)

    Where ρ x — the mass concentration of the target compound calculated from the calibration curve, ug/L;

    V x —Concentrated constant volume of the extract, mL;

    V i — sampling volume of leaching solution, mL
    .

    8.
    Quality Assurance and Quality Control

    (1) Calibration curve

    Use the linear fitting curve to calibrate, the correlation coefficient should be greater than or equal to 0.
    995, otherwise the calibration curve should be redrawn

    .

    (2) Calibration verification

    Before analyzing each batch of samples (up to 10 samples), check the calibration curve with the mass concentration at the middle point of the calibration curve.
    The relative deviation of the measurement results should be controlled within 30%, otherwise the calibration curve should be redrawn

    .

    (Three) blank

    Each batch of samples (up to 10 samples) should be a laboratory blank, and the mass concentration of the target compound in the experimental blank should be less than the detection limit of the method
    .

    (4) Parallel sample determination

    Each batch of samples (up to 10 samples) should be subjected to at least one parallel determination, and the relative deviation of the parallel sample determination results should be within 30%
    .

    Nine, matters needing attention

    (1) The solvents and reagents used in the experiment have a certain degree of toxicity, so the sample pretreatment process should be carried out in a fume hood, and the operator should do his own protection work
    .

    (2) The rotary evaporation should not be too fast and the vacuum degree should not be too low, otherwise it will affect the recovery rate of organic chlorine
    .

    (3) Double columns can be used for qualitative analysis of detected samples, and the accuracy of the results can be judged based on the recovery rate of standard addition
    .

    (4) Before sample injection every day, use DDT standard sample for lysis check.
    The lysis rate is less than 15% before the sample analysis can be carried out.
    Otherwise, clean the liner until the lysis rate is less than 15%

    .

     

     

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