We are running calibration checks on our Varian 9050 absorbance detector. Recently we have been getting Low Lamp Intensity warnings prior to running the samples. Am I correct in assuming that a lowered intensity with the lamp set to detect at a wavelength of 360l that respsonses would be lower than expected? And if that assumption is correct does anyone have any guesses as to why I am seeing 120% response on average?

I do need to also mention that the same calibration check solution was verified at 100% recovery on a seperate system using the same analysis method.

G'day Tina,
My thoughts are that as the intensity of the lamp decreases, then so to does the sensitivity of the detection. At lower light intensities, there is "less" light than normal for the chromophore to adsorb. As such, larger variations may be seen with repeated measurements of the same chromaphore at the same concentration. This may not lead to a decrease in actual detector response, but a lesser degree of accuracy. Your measurement of 120% perhaps confirms this.
In addition, as a lamp ages, the noise becomes greater in it's emission spectrum, and the chance that you are recording noise plus signal may also lead to a 120% response.

Hope that's of some assistance in the least.

regards
Greg

Greg,
Thank you very much! I think that you have helped solve the problem! n I really appreciate your assitance.

Tina