Dear,

Analysisi of mixed K and Na, or other alkaline metals interferes each other by ICP-OES. So you cannot measure potassium precisely with Na. I think better to use flame photometric detector or ion chromatography.

Could I answer adequately?

Best regards

Dear Richard,

when you are going to analyse these alkali metals, low recoveries can occur as there is the danger of spectral interferences. Usually, the spectral intensity of these elements is rather low. I strongly recommend to switch to a different spectral wavelength (even with a lower specific intensity) and check for recovery again. There are databases with spectral lines of all elements and their relative intensities, also warning of potentially interfering spectral 'neighbours'.

Kind regards

Dear,

for alkali elements, when using flame emission or atomic absorption you'll get better performance  than with ICP. Some people still analyze K or Na with "cold" plasma (i.e. 0.8 KW or less). With this settings, plasma works like a flame: signal is improved and background is weaker but you also need the addition of an ionisation buffer (i.e. CsCl) as with flame AAS. For spectral interférences,  766.5nm line risks to be interfered by Mg (considerably less with cold plasma) but 769.9nm, less sensitive, should be free.

Regards,

For the analysis of  alkali and alkali earth elements by ICP, matrix effect and ionisation interferences are problematic. Be sure that matrix matching calibration should be borne in mind. 

Regards,

Dear Richard:

It is very difficult to give a definite answer to your question without more details about what exactly you are doing, what you mean by poor recovery, how much?, what concentration levels you are using, what is the sample matrix, etc.. 

For example, do you get poor recovery with the multi-element standard, relative to single a element standard of K, or the poor recovery in a real sample?

Do you get similar recoveries/suppression from two different wavelengths of K ? 

One good way of trouble shooting for this problem, may be to do a standard addition and see whether it is due to matrix suppression or some spectral interferences, etc..

We can help you better with more specific suggestions, if we can understand your problem better.

Best wishes,

Nimal

Are you sure that you are using a right concentration of K in the standard? If you mix the standard of P and K, you have to consider the concentration of K (as a counter ion for PO4) in the initial P standard.