Improved solid-phase spectrometry for the microdetermination of total and dissolved phosphate

Area of Science:

• Analytical Chemistry
• Environmental Science
• Spectroscopy

Background:

• Accurate determination of phosphate in water is vital for environmental monitoring.
• Existing spectrophotometric methods for trace phosphate analysis often lack sensitivity or require extensive preconcentration.
• Solid-phase spectrophotometry offers potential for improved sensitivity and reduced sample manipulation.

Purpose of the Study:

• To enhance solid-phase spectrophotometry for the accurate determination of total and dissolved phosphate in water.
• To achieve high sensitivity for sub-microgram per cubic decimeter levels of phosphate-P.
• To develop a method suitable for direct analysis of trace phosphate in environmental water samples.

Main Methods:

• Concentration of molybdenum blue species using Sephadex G-25 gel beads.
• Spectrophotometric measurement at 836 nm and 450 nm, utilizing absorbance difference (ΔA) to minimize packing errors.
• Direct determination of trace phosphate in water samples without preconcentration steps.

Main Results:

• Achieved over 100-fold increase in sensitivity compared to solution methods for a 20 cm³ sample.
• Established a detection limit as low as 0.1 µg dm⁻³ for phosphate-P.
• Successfully determined trace levels of phosphate in small stream water samples.

Conclusions:

• The improved solid-phase spectrophotometry method provides a highly sensitive and accurate approach for trace phosphate determination.
• The method eliminates the need for preconcentration, simplifying analysis of environmental water samples.
• This technique is valuable for monitoring water quality and assessing phosphate pollution.