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    Home > Chemicals Industry > Chemical Technology > Analysis conditions for residues of α-Trenbolone, β-Trenbolone, 19-ethylene nortestosterone and epi-19-ethylene nortestosterone in milk and milk powder

    Analysis conditions for residues of α-Trenbolone, β-Trenbolone, 19-ethylene nortestosterone and epi-19-ethylene nortestosterone in milk and milk powder

    • Last Update: 2021-09-20
    • Source: Internet
    • Author: User
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    8.
    2.
    3.
    7 Selection of analysis conditions

    (1) Enzymatic hydrolysis

    Trenbolone and 19-nortestosterone are often stably combined with proteins and other substances in the samples, and the literature mostly uses β-glucuronidase /arylsulfatase hydrolysis
    .
    However, the enzymolysis conditions are different (including the amount of enzyme, enzymolysis temperature and time, different buffer systems and pH, etc.


    )


    (2) Extraction and purification

    Ethyl acetate can effectively extract the residual trenbolone and 19-nortestosterone in the sample
    .
    But milk and milk powder are high protein samples, ethyl acetate cannot precipitate protein, and the extraction solution is easy to emulsify


    .


    Solid phase extraction technology is a relatively effective purification method.
    This method has done experiments on silica gel columns, C 18 columns, mixed columns, immunoaffinity columns, and C 18 -amino columns in series.
    The results showed that C 18 columns and silica gel columns , The purification effect of the mixed column is not good, and the recovery rate is not high
    .
    Considering that GPC has a good ability to remove oleoprotein and other macromolecules, the GPC purification method was tested


    .


    Figure 8-12 GPC chromatogram of mixed standard solution and milk matrix

    (3) Selection of instrument conditions

    1) Selection of chromatographic column and mobile phase

    a-Trenbolone , β-Trenbolone, 19-ethylene nortestosterone and epi-19-ethylene nortestosterone are two pairs of optical isomers with the same molecular weight and characteristic fragments, so the separation of chromatographic conditions becomes the detection Necessary means for these two pairs of isomers
    .
    Using 0.


    1% aqueous acetic acid and acetonitrile as the mobile phase, using time gradient elution, the four substances can be effectively separated on the InertsilODS-3 (2.


    2) Determination of monitoring ions

    A peristaltic pump was used to inject 1μg/mL mixed standard solution at 10uL/min to establish the best mass spectrometry conditions for determining each compound, including selecting characteristic ion pairs, optimizing mass spectrometry analysis conditions such as electrospray voltage, sheath gas, auxiliary gas, and collision energy
    .
    The mixed standard solution of the analyte enters the ESI ionization source, and the analyte is analyzed by the first-level full-scan mass spectrometry in the positive and negative ion scanning modes to obtain the molecular ion peak


    .


     

     

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