ChromiSense: A colourimetric lab-on-a-disc sensor for chromium speciation in water

Area of Science:

• Analytical Chemistry
• Environmental Science
• Microfluidics

Background:

• Chromium speciation in water is crucial for environmental monitoring.
• Existing methods for chromium analysis can be time-consuming and require laboratory settings.

Purpose of the Study:

• To develop a centrifugal microfluidic device for the quantitative analysis of chromium (III) and (VI) species in water.
• To enable rapid, low-cost, and on-site water quality assessment.

Main Methods:

• A colorimetric sensor system, ChromiSense, was developed on a disposable microfluidic disc.
• Centrifugal force was used to mix sample and reagents, initiating a colorimetric reaction.
• Chromium (III) was quantified using 2,6-pyridine dicarboxylic acid, and Chromium (VI) using 1,5-diphenyl carbazide (DPC).
• Absorbance was measured using a low-cost LED and photodiode optical detection system.

Main Results:

• The device achieved limits of detection (LOD) of 21 mgL⁻¹ for Cr(III) and 4 μgL⁻¹ for Cr(VI).
• Linear ranges were determined as 69-1000 mgL⁻¹ for Cr(III) and 14-1000 μgL⁻¹ for Cr(VI).
• Results showed good agreement with benchtop spectrophotometer measurements.

Conclusions:

• The ChromiSense device provides a simple, cost-effective solution for rapid on-site chromium speciation in water.
• Further integration with pre-concentration methods could enhance its suitability for diverse environmental samples.