Impurity in HPLC Water

[carls]

If you leave the vial number blank (no entry) the Agilent 1100 will perform a no injection run. The valve will NOT move from inject to load to inject as in a normal run which eliminates the injector rotor/stator as the source of the problem. The loop is always inline unless you run an injector program.

[thekartis]

check this
http://chromforum.org/viewtopic.php?t=7570

Hope it gives u some idea

[unmgvar]

we had a weird case of a negative peak in the chromatogram kind of like that.
it was stupid really, and we have no idea why it was the behavior we had,
but someone made the runs on a waters RI while the purge was "on" and it gave a negative peak somewhere

[Uros]

I would say, that you have contamination in sampler area (Loop, metering device, needle, needle seat or valve). Try heating water to around 70 Degree celsius, bypass the degasser, and flush the system through the valve position in main pass. Use zero-dead volume insted of column and set the thermostat to max.