The phosphor elemental analysis was performed according to
the variation of Lowry and Lopez method of organic phosphorus determination method by Analytische Laboratorien Prof. Dr.
H. Malissa und G. Reuter Gmbh, Germany [49,50]. The main principle of the method is based on the photometric phosphorus
determination at = 830 nm by converting the phosphate into
phosphomolybdate followed by ascorbic acid reduction. The limit
of quantification is 2 g.