[dbry]

I am having trouble with Na testing on AA.  The testing has been going great and then all of a sudden when running the standards, I am seeing alot of noise and the last two standards are going over the absorbance.  I received a new lamp, but the same thing happened with it. I am getting a same company lamp as the machine, but I could use any help.

[marquis]

Check and see if your AA can also do atomic emission(AE).  Most AA's can be set up to do it.  And it doesn't take a lamp.  You measure the amount of light emitted at the sodium wavelength.  AE is sensitive to elements like sodium.

As for the AA problem, my first guess would be an old sodium lamp.  As the lamp gets old, the noise increases.  You can increase the lamp current.  This will increase the energy of the sodium line.  It will also kill your lamp sooner.  Also, check your sodium lamp.  Many of them have a running time meter on the leads.  It will let you know how long the lamp has been used.  This can help tell you if it is a lamp problem.