Sequential injection analysis for Cr(VI) and Cr(III) with renewable surface reflection spectrophotometry.

Area of Science:

• Analytical Chemistry
• Spectrophotometry

Background:

• Chromium speciation is crucial for environmental and health assessments.
• Existing methods for chromium determination can be complex and time-consuming.

Purpose of the Study:

• To develop a highly sensitive and rapid method for simultaneous determination of chromium(III) and chromium(VI).
• To utilize the chromogenic reaction of chromium(VI) with 1,5-diphenylcarbohydrazide (DPC) on Polysorb C-18 beads.

Main Methods:

• Sequential Injection Renewable Surface Technique (SI-RST) combined with reflect spectrophotometry.
• Utilized the reaction of Cr(VI) with DPC on Polysorb C-18 beads.
• Cr(III) was determined after oxidation to Cr(VI) using ammonium persulfate ((NH4)2S2O8).

Main Results:

• Achieved a detection limit of 2.4 µg/L for Cr(VI) within a linear range of 0.02–0.5 mg/L.
• Demonstrated high precision (1.3% RSD for Cr(VI), 2.5% RSD for Cr(III)) and a throughput of 53 samples/hour.
• Validated for simultaneous determination in water samples with an error less than 3% and average Cr(III) recovery of 99.1%.

Conclusions:

• The proposed SI-RST reflect spectrophotometric method offers a sensitive, precise, and rapid approach for chromium speciation.
• This method is suitable for the simultaneous determination of Cr(III) and Cr(VI) in environmental water samples.