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    Home > Chemicals Industry > Chemical Technology > Determination of Carbonyl Compounds in Organic Chemical Products (2)

    Determination of Carbonyl Compounds in Organic Chemical Products (2)

    • Last Update: 2022-01-19
    • Source: Internet
    • Author: User
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    4.
    2.
    4.
    2 Determination of samples

    4.
    2.
    4.
    2.
    1 Preparation of sample solution

    Pipette 2.
    0mL of laboratory samples containing carbonyl compounds (0.
    5-50)ug into a pre-weighed 25mL volumetric flask, and weigh to the nearest 0.
    0001g

    .
    The difference between the two weighings is the quality of the laboratory sample,

    Note: If the content of carbonyl compounds in the 2.
    0mL sample exceeds 50ug, it can be released to the sword degree with carbon-free methanol first, then double press 4.
    2.
    4.
    2.
    1 for determination, and increase the dilution factor when calculating the result

    .

    4.
    2.
    4.
    2.
    2 Determination of absorbance

    Operate in accordance with 4.
    2.
    4.
    1.
    2

    .
    At the same time, transfer 2.
    0 mL of carbonyl-free methanol for a blank test

    .

    4.
    2.
    5 Result calculation

    The mass fraction w 1 of the carbonyl compound is calculated in terms of carbonyl (CO), and the value is expressed in %.
    Calculated according to formula (1):

    Where:

    m 1 —The value of the mass of the carbon-based compound obtained from the standard online check corresponding to the absorbance of the sample, in micrograms (ug);

    m 0 —The value of the mass of the carbonyl compound found on the internal standard curve corresponding to the blank absorbance, in micrograms (ug);

    m—The value of the mass of the sample, in grams (g)
    .

    4.
    3 Volume method

    4.
    3.
    1 Principle of the method

    The carbonyl compound in the sample reacts with hydroxylamine hydrochloride .
    The acid generated is indicated by bromophenol blue and
    titrated with
    sodium hydroxide standard titration solution to calculate the content of the carbonyl compound
    .

    Reaction formula: RCHO+H 2 NOH·HCl=RCH=NOH+HCI+H 2 O

    RCOR'+H 2 NOH·HCI=RR'C=NOH+HCI+H 2 O

    4.
    3.
    2 Reagents and solutions

    4.
    3.
    2.
    1 95%
    ethanol ;

    4.
    3.
    2.
    2
    Hydroxylamine hydrochloride solution: 20g/L;

    Weigh 4g of hydroxylamine hydrochloride, dissolve it in a 250mL iodine flask containing 20mL of water, dilute with 95% ethanol to 200mL, reflux in a boiling water bath for 30 minutes, cool to room temperature, add 5.
    0mL bromophenol blue indicator solution, and use
    hydrogen The sodium oxide solution is neutralized to produce dichroic green (dichroic green)
    .
    This solution was made up a month ago

    .

    4.
    3.
    2.
    3 Sodium hydroxide standard titration solution: c(NaOH)=0.
    1mol/L;

    4.
    3.
    2.
    4 Sodium hydroxide solution: c(NaOII)=0.
    01mol/L;

    4.
    3.
    2.
    5 Hydrochloric acid solution: c(HCl)=0.
    01mol/L:

    4.
    3.
    2.
    6 Bromophenol blue indicator solution: 2g/L

    Weigh 0.
    2g of bromophenol blue indicator, add 1.
    5mL of 0.
    1mol/L sodium hydroxide standard titration solution to dissolve, and dilute to 100mL with 95% ethanol

    .

    4.
    3.
    3 Instruments

    Micro burette: 10mL
    .

    4.
    3.
    4 Analysis steps

    Measure 50 mL of hydroxylamine hydrochloride solution and place it in a 250 mL iodine measuring flask as a standard color for titration
    .

    Pipette 50.
    0mL laboratory sample into a 250mL iodine measuring bottle towel, add 1.
    25mL bromophenol blue indicator solution: dropwise add sodium hydroxide solution or hydrochloric acid solution until the sample solution is consistent with the standard color, this is the sample solution

    .

    Add 25.
    0 mL of hydroxylamine hydrochloride solution to the sample solution, gently move the stopper of the iodine flask, cover it, put it in a boiling water bath for 10 minutes, cool to room temperature, and titrate with sodium hydroxide standard titration solution to the standard color For the end

    .
    When the color change of the end point is not obvious, the end point can be determined according to the potentiometric titration method of GB/T9725-2007

    .

    4.
    3.
    5 Result calculation

    The mass fraction w2 of the carbonyl compound is calculated as carbonyl (CO), and the value is expressed as %, calculated according to formula (2):

    Where:

    V—The value of the volume of the standard titration solution (4.
    2.
    3.
    2) of sodium hydroxide consumed by the sample, in milliliters (mL);

    The value of the density of the sample at p-20℃, the unit is grams per liter (g/L);

    M—the value of the molar mass of the carbonyl group, in grams per mole (g/mol) [M=28.
    01];

    c—The value of the concentration of the standard titration solution of sodium oxide, in moles per liter (mol/L)
    .

    5 Presentation of results

    Take the arithmetic mean of the two parallel determination results as the determination result
    .

    If the carbonyl compound is expressed in other forms, multiply the results of formulas (1) and (2) by E/28.
    01, where E is the relative molecular weight of the carbonyl compound in this form

    .

    Related Links: Determination of Carbonyl Compounds in Organic Chemical Products (1)

     

     

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