Buffer A contains 25mM MES pH 6 10mM NaCl and 10mM BME buffer B contains 25mM MES pH 6 500mM NaCl and 10mM BME. When we run an increasing gradient of buffer B for ion exchange protein purification the UV baseline drifts negatively. We have narrowed it down to increasing conductivity causing the UV negative drift but we aren't sure why or what to do to fix it.
Hi there,
If BME in B is somewhat smaller tan in A then UV should decrease during gradient as BME contributes to UV signal.
Buffers are less then two weeks old, we combine all ingredients other than BME and spike small amounts with BME as we need the buffer. There is 10mM BME in both buffers. we ran only 500mM NaCl through the instrument and this caused the UV to drift negatively, ddH2O alone causes a positive drift and pure 25mM MES causes a less steep positive drift (we think the slower positive drift is related to the very low conductivity reading MES gave). That is what leads us to believe it is somehow correlated with conductivity.
Well, if the signal is not stable during an isocratic run then there is definitely something wrong with your detection.
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