1：Experimental Design and Method Selection:

The method was conducted in three stages: preparation, testing, and data processing. Preparation involved making standard and reagent solutions. Testing involved analyzing phosphorus standard and P2O5 samples from inorganic fertilizer for linearity, precision, accuracy, limit of detection, and limit of quantitation. Data processing involved statistical analysis of results against standard method requirements.

2：Sample Selection and Data Sources:

Inorganic fertilizer samples were used, with phosphorus standard solutions prepared from KH2PO

3：List of Experimental Equipment and Materials:

Volumetric glass, analytical balance, magnetic stirrer, hot plate, filter paper, and spectrophotometer UV-Visible (Agilent Technology Carry 60). Reagents included KH2PO4, HClO4, HNO3, NH4VO3, (NH4)5.Mo7O24.4H2O, and distilled water.

4：0). Reagents included KH2PO4, HClO4, HNO3, NH4VO3, (NH4)Mo7O4H2O, and distilled water. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: Sample preparation involved destruction with HClO4 and HNO3, heating, and filtration. Standard solutions were prepared and measured at λ = 420 nm. Precision and accuracy tests were conducted with repeated measurements and spike recovery tests, respectively.

5：Data Analysis Methods:

Statistical analysis included calculation of coefficient determination (R2), precision (% RSD), accuracy (% recovery), LOD, and LOQ.