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SCD 355 loosing sensitivity over time

kake

Hi - we have an old SCD 355 coupled to a GC×GC instrument running sulfur speciation in petroleum samples.

Over the last 5 years the sensitivity of the detector has decreased significantly, which in practice is seen as elevated background noise and thus a lower limit of detection.

We have considered changing the reaction cell to regain the sensitivity - any experience on the effect of such a replacement?

Looking forward to receiving your expert inputs :-) BR Karina

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  • 0

    Hi kake

     

    I used SCD for more than 5 years . it is one of best selective detector for sulfur but only limitation there is losing signal by the time .

     

    What is your signal reading in ozone on and ozone off position ?

    Did you change you regulator or sampling system recently ?

    How frequently you are using the analyzer with sulfur sample?

    just Try following passivation procedure :

    1. Connect the SCD with high conc of sulfur ( 30 ppm H2S/N2)
    2. Increase the oven temperature to 100 C
    3. Leave this condition over night
    4. Now your regulator ,  line and system is totally passivated
    5. Next day purge system with pure nitrogen for three cycles
    6. decrease the temp
    7. check your sample again and notice the difference in sulfur peak area comparing to before passivation area
Reply
  • 0

    Hi kake

     

    I used SCD for more than 5 years . it is one of best selective detector for sulfur but only limitation there is losing signal by the time .

     

    What is your signal reading in ozone on and ozone off position ?

    Did you change you regulator or sampling system recently ?

    How frequently you are using the analyzer with sulfur sample?

    just Try following passivation procedure :

    1. Connect the SCD with high conc of sulfur ( 30 ppm H2S/N2)
    2. Increase the oven temperature to 100 C
    3. Leave this condition over night
    4. Now your regulator ,  line and system is totally passivated
    5. Next day purge system with pure nitrogen for three cycles
    6. decrease the temp
    7. check your sample again and notice the difference in sulfur peak area comparing to before passivation area
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