High frequency noise when heating the detector?

[ZCG]

I have a waters 410 RI detector, 515 pump, 717plus autosampler, and BioRad HPX-87H column. The mobile phase I am using is .005 M sulfuric acid in water. Normally I run the column and RI detector at 50 C. Recently, the system was shut down for two weeks. Upon starting everything back up I noticed that the detector reading was changing rapidly and appeared to be changing randomly. I flushed the cell with water/15% nitric/water/isopropanol/water/mobile phase. This seemed to remove any bubble/contamination and give a steady baseline. Upon heating, the high frequency noise returned. I cleaned the cell again and had a stable baseline at room temp. for 24 hours. When I heated to 35 C, the noise returned. When I cool the detector back to room temp the noise doesn't go away unless the cell is cleaned. Any thoughts on what might be causing this? I'm thinking a leaky cell, but I am relatively new to HPLC.

[tom jupille]

The fact that the noise persists when you cool it back down until you flush the cell points toward a bubble problems. Is your degasser functioning properly?