I'm trying to collect measurements on a solution in water in the 1050-1200nm range. To determine the sensitivity in this range, I've acquired measurements on pure HPLC deionized water in double-beam mode using two identical Suprasil cuvettes. I have taken measurements at several time steps near 1064 nm, from 0.1-100 s per timepoint at 0.1 nm per step (2 nm bandwidth). I keep finding that the average baseline near 1064 nm is slightly negative, and the baseline SD does not improve beyond 1.4e-4 Abs.
This value is technically below the acceptable qualification values of 2e-4 Abs in that range, but I'm trying to determine if this is the ultimate noise level of the instrument in this range given the impressive specs given for this instrument.
It is also odd to see this periodic, repeatable variation in the data at such small spectral steps. Are these due to a mechanical issue in the monochromator like a sine bar issue, or due to environmental or electrical line noise of some kind? I've inquired with Agilent's spectroscopy team numerous times and have yet to get a response, I'm hoping this forum can shed some light on the issue!