Simultaneous determination of phosphite and phosphate in fertilizers by Raman spectroscopy

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Agricultural Science

Background:

• Raman spectroscopy is a powerful tool for identifying phosphorus oxyanions.
• Simultaneous determination of phosphite and phosphate in solutions remains challenging.
• Accurate analysis of phosphorus species is crucial for fertilizer quality control.

Purpose of the Study:

• To develop a Raman spectroscopy method for simultaneous determination of phosphate and phosphite in fertilizers.
• To optimize analytical conditions, including pH, for selective detection.
• To validate the method's accuracy, linearity, and sensitivity.

Main Methods:

• Raman spectroscopy was employed to analyze phosphate (PO4) and phosphite (PO3) in fertilizer samples.
• The influence of pH on spectral analysis was investigated, with optimal selectivity achieved at pH 10.0.
• External calibration was used, and results were compared with a spectrophotometric method.

Main Results:

• Selective detection of phosphate at 874 cm⁻¹ and phosphite at 2321 cm⁻¹ was achieved at pH 10.0.
• The method demonstrated a linear working range of 0.15%-6.20% (w/v) P with high regression coefficients (r > 0.9945).
• Low limits of detection (0.10% P for PO4, 0.05% P for PO3) and good recoveries (92-110%) were obtained.

Conclusions:

• Raman spectroscopy provides an accurate and selective method for simultaneous determination of phosphate and phosphite in fertilizers.
• The optimized method is suitable for routine analysis of phosphorus species in commercial fertilizers.
• The findings align with established spectrophotometric methods, validating the proposed Raman spectroscopy approach.