A soft material for chromium speciation in water samples using a chemiluminescence automatic system

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Materials Science

Background:

• Chromium speciation is crucial for assessing water quality and environmental impact.
• Existing methods for chromium speciation can be complex and time-consuming.
• Novel sorbent materials are needed for efficient and accurate chromium analysis.

Purpose of the Study:

• To develop a new method for chromium speciation in natural waters.
• To utilize a novel soft material composed of multiwall carbon nanotubes and 1-butyl-3-methyl imidazolium chloride as a sorbent.
• To establish a fully automated flow-batch analysis system for quantifying Cr(VI) and Cr(III).

Main Methods:

• A multicommutated flow system with a minicolumn packed with the novel soft material was designed.
• The sorbent selectively retains Cr(VI) while allowing Cr(III) to pass.
• Chemiluminescence detection was employed, with Cr(III) acting as a catalyst and Cr(VI) as an oxidant in luminol reactions.

Main Results:

• The developed method demonstrated low limits of detection: 1.4 μg/L for Cr(VI) and 4.0 μg/L for Cr(III).
• High precision was achieved, with relative standard deviations of 3.8% for Cr(VI) and 7.0% for Cr(III).
• The method showed excellent performance in real water samples, with recoveries ranging from 95% to 107%.

Conclusions:

• The novel soft material and automated flow system provide an effective approach for chromium speciation in natural waters.
• This method offers a new analytical strategy, particularly the use of Cr(VI) as an oxidant in luminol chemiluminescence, which has not been previously reported.
• The results are comparable to those obtained using the inductive coupled plasma-optical emission spectrometry technique, validating the method's reliability.