[RASMB] XL/I absorbance problem

[Leech, AP]

Hello all,

I'm not rally happy with the noise I'm seeing on my XL/I's
absorbance scans, and I have a few queries. I'd be grateful for
any comments.

1. Noise seems excessive even on reasonable samples. Scans on
an empty hole at 280 nm give an overall flat profile (in A280)
but peak noise is +/-0.05. More peculiar is that the noise seems
to be spikes, randomly distributed along radius and not in the
same place on successive scans. (For comparison our old XL/A has
peak to peak noise +/- 0.015 under the same conditions)

2. Using the request data intensity option, the overall profile
has a dip at r=6.3, but also numerous spikes, mostly upwards
of about 600 counts on a background of 6000. Cleaning if anything
has made this worse. (Cf about 3000 for the XL/A which does need
cleaning.)

3. A wavelength intensity profile looks normal though the maxima
are not great (16000 at 230 nm after cleaning, 11000 before).

4. What does the "request data incident" option in the GUI do?
For the XL/A this produces very flat lines with some spikes upward
or downward, of constant size; for the XL/A reasonably flat lines
with random noise superimposed (4000 +/-100). As I don't know what
this is measuring, I'm not sure what to expect.

I'll try and post some graphs later.

Many thanks,

Andrew

-- 
Dr Andrew Leech                   *  Laboratory Manager
Technology Facility               *  Molecular Interactions Laboratory
Department of Biology (Area 15)   *  Tel   : +44 (0)1904 328723
University of York                *  Fax   : +44 (0)1904 328804
PO Box 373,  York  YO10 5YW       *  Email : apl3 at york.ac.uk