Co, Br, Mn in TPA and PTA

    Application Note XRT1539

    XRT1539 Co Br Mn banner


    On-line measurement of cobalt (Co), bromine (Br), and manganese (Mn) in terephthalic acid (TPA) is demonstrated. 


    Terephthalic acid (TPA) and purified terephthalic acid (PTA) are precursors in making polyester PET for polyester films, PET bottle resin, textile fabrics, and specialty chemicals. During production and use of TPA and PTA, the Co, Br, and Mn catalysts must be closely monitored to ensure optimum product quality. Since TPA and PTA are aggressive solutions, an on-line measurement is ideal. Continuous monitoring minimizes lab testing requirements, allows for process optimization, and is critical in ensuring the end product meets specifications. The Rigaku NEX OL offers simple and low maintenance on-line analytical technique for trending your process streams. Results are communicated to your plant DCS (distributed control system) via 4 – 20 mA current loops or MODBUS® over an Ethernet connection allowing for real-time, closed-loop control.

    NEX OLModel: NEX OL

    MODBUS is a registered trademark of Schneider Electric USA, Inc.


    An empirical calibration was built using a set of 8 standards. To demonstrate performance, water-based standards were introduced through the auxiliary sample input loop and analyzed in a static position.

    Component Concentration range (ppm)
    Co 150-650
    Br 360-1800
    Mn 50-1000

    Repeatability (Precision)

    To demonstrate repeatability (precision), samples containing low and high amounts of Co, Br, and Mn were chosen from the set of calibration standards. Each sample was measured in a static position for ten repeat analyses.

    xrt1539 Cobalt 48 Hr Trend

    Co   Units: (ppm)

    Sample I.D. Standard value Average value Std. dev % Relative
    8 650 653 5 0.8
    1 150 147 4 2.7
    3 223 220 4 1.8

    xrt1539 Bromine 48 Hr Trend

    Br   Units: (ppm)

    Sample I.D. Standard value Average value Std. dev % Relative
    8 1185 1181 5 0.4
    1 966 962 4 0.4
    3 362 365 2 0.6

    xrt1539 Manganese 48 Hr Trend

    Mn   Units: (ppm)

    Sample I.D. Standard value Average value Std. dev % Relative
    8 999 994 9 0.9
    1 50 46 5 10
    3 864 869 8 0.9

    NEX OL features and benefits

    • XRT1306 screenReal-time process control
    • Trend analysis charting
    • Capable of measuring elements Al to U, depending on application
    • Robust Rigaku NEX QC+ optical kernel with SDD detector
    • Industrial touchscreen user interface
    • Unique toolless flow cell design
    • No dangerous radioisotopes


    The NEX OL offers real-time on-line trend analysis in a simple yet powerful and versatile system for quantifying the elemental composition of a process stream. The results of this study indicate that given stable samples, proper sample handling, and proper calibration technique, the Rigaku NEX OL EDXRF can achieve excellent results in monitoring the concentration of Co, Br, and Mn in TPA and PTA solutions.

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