Weird dips in diode array baseline

[bisnettrj2]

I'm having a problem with my Diode Array detector (Agilent G1315A). I'm running 52:48 DI H2O:Methanol isocratic, using 210 and 254 nm, both referenced at 350 with a bandwidth of 100. I'm using an Agilent 1100 setup, (binary pump, online degasser, thermostatted column compartment, autosampler). The detector has been doing this for the last week or so, and has done it with two different columns. Any ideas?

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[tom jupille]

Random dips, or do they always occur at or near the same time in a chromatogram? And do they also show up in blanks?

If they occur at predictable times, the try disabling the reference wavelength. If something in your sample (or blank) absorbs at 350, it will force a negative dip.

[bisnettrj2]

It's somewhat random- it occurs at roughly the same time in the run, but I've also seen it earlier or later. I'll try disabling the reference wavelength and see if that fixes it. Thanks for the tip.