254 m is what we use to sterilize and some chromotography plates have a dye that will fluoresce at that wave length, we use a geologist dual tube lamp for this, you are spot on with what i meant, I was distinguishing between the shorter UV and the safer longer UV wavlenghs used, though for some reason I had 450nm in my head! but that likely me getting it mixed up. The type of FGP being used has to use the longer UV or the organism is killed off, the longer wavelengh is just enough to excite the protein and fluoresce, the plasmids for coding the FGP are inserted manually into the bacteria, population growth is then estimated using reflected UV in a special chamber.
We did use quatz curvettes but now have funny little plastic chambers with a window in them on the main tri port take off lines. The led packet says 420nm! Which i know is wrong!! So must be 400nm, these are a rough test before we buy the high quality Leds.
So from what your saying we simply use a known blank to 'zero' the reading each time we do a run, that seems like a reasonable idea then. My concern was them drifting off while being used, i have a UV/Vis spectrometer thats getting on, the white Deuterium bulb does drift over time and costs alot to replace, again though these are intended to be zeroed for each sample, the UV leds sound like its only needed each run and not each sample, that will save alot of time.
The shorter wave UV gives you 'arc eye' if you look at it long enough, ive had it a couple of times and its really painful!