Trace level of Na in Zn

[Les Moore]

Hi,

We have trace level Na in our Al-Zn mixture and it often decides to leave the bath as vapour through refractories.  The Zn also does similar and we get clear evident Zn & Al presence in our refractories but .... the question has now been asked.  Just what does the Na do? 
There is some evidence that it facilitates the breakdown of SiC to Si, Al and C into some form of ultrafine ternary eutectic.
In tests:
If you have just straight liquid Zn zinc, the refractory is fine.
If you have Al & Zn, the refractory has minor problems and the rate of degradation is quite acceptable.
If you have Al & Zn and put a small aount of Na, the problems are dramatic.

So, how can I analyse trace levels of Na in the presence of major Zn?
The refratory is a mixture of large, medium and small (10um) SiC grains bonded together with small (<5um) Al2O3 and the metallic penetration between the grains is ~200nm.

All simple answers will be rewarded with a beer. 

[Probeman]

So, how can I analyse trace levels of Na in the presence of major Zn?
The refratory is a mixture of large, medium and small (10um) SiC grains bonded together with small (<5um) Al2O3 and the metallic penetration between the grains is ~200nm.

All simple answers will be rewarded with a beer. 

Hi Les,
The simple answer is to use my quantitative interference correction. It works well for trace  Na in Zn.
john