d. Measurement

	- *Create a calibration curve using known concentrations of phosphate standards treated with the same reagents and procedure.*
	- *Use the calibration curve to determine the concentration of DRP in the sample based on its absorbance value.*
	- *Include blank samples (water without phosphate) and perform replicate measurements to ensure accuracy.*
	- *Regularly calibrate the spectrophotometer using standard solutions.*
	- *Express the results in units of phosphorus concentration, such as mg/L or <sup>μ</sup>g/L.*
