Dear Heba,

Please provide more details on your problem; Like the step at which you are facing trouble.

Nevertheless,

*if precipitation occurs during preparation reagent solution, you should manage dissolving completely solid reagents before adding sulfuric acid;

*if it occurs during heating, manage maintaining temperature at 90 °C (avoid boiling);

*Also think about diluting your sample if precipitation occurs during mixing or heating at 90 °C.

The procedure we used in attached publication can be of help.

Regards!

@Pierre Nobossé

Thanks a lot for your response. The molybdate reagent usually seems disdolved but during the incubation at 95 ppt forms even in the control. I'll try reducing the incubation temperature to 90 as you recommended and see what's going on.

thanks again sir

Best Regards

Hello, reference method require 95*C 90min. I think nothing will happen is you use 90 instead 95*C. What really can happen you shuld perform your own validation).

Reference method attached.

Good luck!

@Karen A. Darbinyan

Thanks a lot for your answer and reference.

Hello @Heba

Another major recommendation is that the reagent solution should (or MUST) be freshly prepared.

Regards!