ASTM D7884-13 Determination of Carboxybenzaldehyde and Toluic Acid

ASTM D7884-13 Determination of Carboxybenzaldehyde and Toluic Acid

ASTM D7884-13 determines the 4-Carboxybenzaldehyde (4-CBA) and p-Toluic acid (p-TOL) in purified terephthalic acid (PTA) by reverse-phase high-performance liquid chromatography (HPLC). The values are expressed in the SI unit.


    ASTM D7884-13 is useful to create specifications and as an internal quality control tool in places where these items are manufactured or used. The presence of 4-CBA and p-TOL slow down the polymerization process and 4-CBA colorize the polymer due to thermal instability.


    PTA sample is dissolved in ammonium hydroxide solution and a fixed volume of ammonium hydroxide solution is introduced into a high-performance liquid chromatograph equipped with a UV detector. The contaminants 4-CBA and p-TOL are separated from PTA using a C18 chemically bonded column. For quantification, an external standard calibration is used.

    Specimen size:

    The temperature should be maintained at a constant 61°C within the range of 20 to 70°C.


    Calculate the concentration of 4-CBA or p-TOL in mg/kg, using the following equation:

                                      X = ms ·A·Cs ÷ m·As


    X = concentration of 4-CBA or p-TOL in the PTA sample, mg/kg,

    A = peak area of 4-CBA or p-TOL in the PTA sample,

    m = weight of the PTA sample, g,

    As = peak area of 4-CBA or p-TOL in the PTA standard,

    Cs = concentration of 4-CBA or p-TOL in the PTA standard, mg/kg,

     ms = weight of the PTA standard, g.


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