About the deuterium lamp life

[Tequila]

Dear members of this forum,

Yesterday I am working with sodium valproate, I am doing the dissolution test and I noticed that the height of the peak were the half I was obtained two months ago and I started to think the reasons of the reduction of this parameter.
Afther checking all the technique if I did or no an error, I started to suspect that the problem could be the age of the deuterium lamp the manufacturer recomend to change after 1000 hours of using.
I would like to know if the condition of the deuterium lamp could be or not or other reasons that could be the reduction of the height of the peak.
The height is the half of I obteined two months ago.
Thanks in advance for your help,

Diego Delmonte

[HW Mueller]

You don´t have a lamp test integrated in your detector?
Note that the Beer-Lambert Law relates concentration to a ratio, I/Io (light intensity with sample/light intensity without sample). The lamp intensity cancels, unless there is so little light that it can no longer be measured correctly (that´s ~ when lamp tests fail).

[Mark Tracy]

The most common symptoms of a worn out D2 lamp are excessive noise in the baseline and random spikes in the signal. Also difficulty in starting the lamp. Most lamps are rated for 2000 hours of operation, but sometimes will go three times that, or sometimes not. There should be an hour meter either attached to the lamp or computed by the detector. How many hours on your lamp?

[josebenjamin]

Dear Tequila,

It sounds unlikely that lamp age is the source of your problems. I am assuming you are doing HPLC with UV detection. test some other instrument conditions such as injection accuracy or sample preparation before going to the lamp.

Deuterium lamps are still a weak point in technology. Not all lamps are good, the lifetime is not uniform, and they are expensive (what else?). Your lamp may have a timer attached to it that will tell you the approximated time spent thus far, also, as mentioned in some other messages, many detectors have an energy test and will tell you when the level is too low to function properly.

Good Luck,


josebenjamin (guadalajara)

[John]

Tequila,

The signs of a dying D2 lamp are:
High noise.
Drifting baseline / bizarre features on plots.
Flat line (dead).

Areas should remain the same. One parameter you may have overlooked is a change in the signal output of your detector. On our Shimadzus, we have settings for the analogue output we use; either 1 AU/V, 0.5, 2 etc. This may very well explain your phenomenon.

Our D2 lamps have been known to last for a year, switched on 24/7. We record the 220nm power(ref) upon installation and change them when the energy gets below about 30% of installation power.
D2 lamps deteriorate by losing D2. This happens at a greater rate when the lamp is lit. It has been said that lamp life decreases by 40 hours when the lamp is cooled and reheated, so switching it off for a while when not in use does't usually help.

JW