How to measure t0 with Waters2465 ECD?

Hi,
We have started using Waters Electrochemical detector 2465 together with an Alliance and have a question regarding the determination of k’. In order to determine k’ we need a value/time for t0 .Previously we have used an electrochemical detector from Agilent and then we used the first disturbance on the baseline for t0. The value for t0 was then around 0.8 min.When using the Waters ECD the first disturbance on the baseline appeared around 0.2 min which didn’t seem reasonable.Does anyone have a suggestion for how we could determine t0 while using Waters ECD?/ Thomas

Answers

  • Hi Thomas

    Most of the contribution to the t0 comes from the column. You can estimate the volume of mobilephase in the column by the simple formula : 0.5 x D2 x L. D = Column ID in mm, L = column lenght in mm.

    This will give you the column volume in ul. If you add 50ul (contribution from the tubing) to this value you will hvae a good estimat of t0

    best regards

    Rune

  • Thanks,

    We need to be able to determine a value for t0 in every analysis we make. We have done a test using a mixture of water and mobile phase and tested with different injection volumes (2-30µl), see attached. The first disturbance on the baseline which correlates to the injection volume is a negative peak, see attached file.  Our idea was then to use the retention time for the negative peak as t0.

    Is this a reasonable way to determine a value for t0? For UV-detection NaNO3 is used but we're not sure what to use for Electrochemical Detection.

  • Hi

    Yes this seems to be a good determination of t0.

    best regards

    Rune

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