Jan

On 23 Jan 2002, at 15:38, Jan Vermeulen wrote:

> My name is Jan and I work with a PDZ-europe system ANCA-GSL.
> I have a question: I have measured some (NH4)2SO4 and KNO3 that we have
> bought 2 years ago. My question is: can it be that the delta value of
> these bottles changes in function of the time??
> I have got a change from -9.005 to -4.46247 for KNO3 and a change
> from -7.52 to 1.137086 for (NH4)SO4. The first ones where measured at
> 07/06/2000 and the second ones at 17/01/2002.
> These are not standards, I have bought them with Merck Eurolab.

I would be surprised if they changed that quickly. In a similar line
we did not observe a change over three years with shelf reagents.

Two points come to mind:

1) Did you get the same efficiency of combustion of the N in boh
runs?

2) Did you have enough N to be in the linear range of response?

Yours

Andrew Johnston


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