ZAF corrected spectral interference vs count interference

[Ben Buse]

Hi,

Can anyone explain the following. I'm measuring S and correcting for Mo interference. So I have a high purity 316H steel (16.9 Wt. % Cr; 2.25 wt % Mo; 11.9 wt % Ni and 66.73 wt % Fe) - which I assume has no sulphur (datasheet <0.002 wt %).

I use 316H as the interference standard, specify the interfere in standard assignments, when I click analyse the sulphur content goes from 400 ppm (without interference correction) to 60 ppm with interference correction. Now why does it not go to 0 ppm? Now I've also analysed the 316H standard as an unknown and get a similar number.


If I use the "old" count method ratio of counts on S Ka to counts on Mo Ka for 316H (assumed blank). Use this ratio*measured Mo Ka to correct the unknown 316H data - I get 0, 10, 10, 20 ppm for the different spectrometers. (I'm measuring S on 4 spectrometers),.

Thanks

Ben

[Probeman]

Hi,

Can anyone explain the following. I'm measuring S and correcting for Mo interference. So I have a high purity 316H steel (16.9 Wt. % Cr; 2.25 wt % Mo; 11.9 wt % Ni and 66.73 wt % Fe) - which I assume has no sulphur (datasheet <0.002 wt %).

I use 316H as the interference standard, specify the interfere in standard assignments, when I click analyse the sulphur content goes from 400 ppm (without interference correction) to 60 ppm with interference correction. Now why does it not go to 0 ppm? Now I've also analysed the 316H standard as an unknown and get a similar number.


If I use the "old" count method ratio of counts on S Ka to counts on Mo Ka for 316H (assumed blank). Use this ratio*measured Mo Ka to correct the unknown 316H data - I get 0, 10, 10, 20 ppm for the different spectrometers. (I'm measuring S on 4 spectrometers),.

Thanks

Ben

Hi Ben,
You get the same 60 PPM whether you use the aggregate feature or not?   What are you using as an interference standard?

Could there be another element interfering with S Ka?     Have you tried analyzing S in say pure Mo?   Or against another simple Mo compound?  Say Mo oxide?
john

[Ben Buse]

Thanks, yes aggregate works fine - with/without similar number.

The interference standard is 316H

I don't think there is anything else interfering with sulphur & I'm struggling to understand why that would affect the interference correction for the interference standard and the unknown are the same material.

Trouble with using pure Mo or Mo oxide is the Mo peak is much wider and higher and therefore can't be used for the lower contents - although it might be worth testing it.

Ben