[dastgir]

Dear All,

During the estimation of phosphate as "P2O5" by Ammo. Vanadomolybdate method using Thermo Scientific Spectrophotometer, the absoption shown by the sample is continuously changing.

The problem in the instrument is ruled out by the fact that estimation for other species such as
Chloride, SOX and NOX are not showing any such variability.

The sapmle is of Phopho gypsum.

Kind Regards,

Gulam Dastgir

[kevins]

Because of the sample contains gypsum ===> contains calcium which will react with the phosphate to form a insoluble calcium phosphate (I guess). Please try to remove the calcium in the sample preparation or digestion stage.