Seesuan et al. (2025) develop a colorimetric sensor for hexavalent chromium (Cr(VI)) detection using a deep eutectic solvent (DES)/EDTA system as both the extraction and chromogenic medium. The method is validated in water and soil matrices.
Key numbers
LOD: 0.056 mM Cr(VI), equivalent to approximately 2.9 mg/L (2,900 µg/L = 2,900 ppb) in the measured solution after extraction. This LOD is high relative to food or drinking water regulatory levels for Cr(VI). The WHO guideline for total chromium in drinking water is 50 µg/L; the LOD of ~2,900 µg/L means this sensor is appropriate only for grossly contaminated matrices (industrial wastewater, heavily polluted soil), not for regulatory compliance.
Validated in: water and soil. No food matrix validation.
Note: This sensor specifically targets Cr(VI), which is the HMT&C-relevant chromium species. Total chromium must never be substituted for Cr(VI).
Methods (brief)
DES/EDTA-based chromogenic complexation for Cr(VI). Visual colorimetric readout. Environmental matrices only. LOD inadequate for food or drinking water compliance testing but potentially useful for hot-spot industrial contamination screening.
Implications
Testing: LOD of ~2,900 ppb Cr(VI) in solution limits applicability to heavily contaminated environmental scenarios. Of marginal relevance to food testing. The wiki should note this as an illustration of the challenge of achieving food-relevant LODs with simple colorimetric approaches for Cr(VI).