Determination of phosphate in urine by sequential injection analysis

Area of Science:

• Analytical Chemistry
• Clinical Chemistry
• Environmental Chemistry

Background:

• Accurate phosphate determination in urine is crucial for diagnosing various metabolic disorders and assessing kidney function.
• Existing methods may suffer from interferences or require complex procedures, necessitating simpler and more robust analytical approaches.

Purpose of the Study:

• To present and compare two novel, simple turbidimetric methods for quantifying phosphate in urine.
• To evaluate the analytical performance and identify potential interferences for each method.
• To offer greener alternatives for phosphate analysis in clinical and environmental settings.

Main Methods:

• Method 1: Determination of phosphate based on calcium phosphate crystallization.
• Method 2: Determination of phosphate based on its inhibitory effect on calcium carbonate crystallization.
• Interference from high calcium concentrations in Method 1 was resolved using a cation exchange resin.

Main Results:

• Calcium phosphate method: linear range 0.2-1.5 g L⁻¹, limit of detection (LOD) 14 mg L⁻¹, relative standard deviation (RSD) 1.1-2.0%.
• Inhibitory method: linear range 0.1-1.8 mg L⁻¹, LOD 0.01 mg L⁻¹, RSD 0.97-1.90%.
• The inhibitory method demonstrated higher sensitivity and a broader linear range compared to the calcium phosphate method.

Conclusions:

• Both turbidimetric methods provide simple and efficient means for urine phosphate determination.
• The inhibitory method is more sensitive and robust, especially when high calcium levels are present.
• The developed methods utilize low-toxicity reagents, aligning with the principles of Green Analytical Chemistry.