Why in news?
Researchers at Bengaluru’s Raman Research Institute (RRI) have developed a simple technique using the “coffee‑stain effect” to detect harmful dyes such as Rhodamine B in food and water. The method promises affordable, sensitive testing for contaminants.
Background
Rhodamine B is a synthetic xanthene dye that produces a bright pink colour. It is widely used in textiles, cosmetics and scientific research but is banned as a food additive and tightly regulated in cosmetics. Studies show that exposure can cause DNA damage, mutations and tumour formation in animals. Detecting trace amounts in food and drink is therefore critical for public health and safety.
The coffee‑stain detection technique
- Nanorod rings: Scientists mixed gold nanorods into water. When a drop of this mixture dries on a surface, it forms a ring pattern due to the coffee‑stain effect. These rings create “hotspots” that amplify Raman signals.
- SERS detection: Using surface‑enhanced Raman spectroscopy (SERS), the researchers detected Rhodamine B at concentrations down to parts per trillion. The gold nanorod ring acts as a sensor, enhancing the Raman signal of the dye molecules.
- Portability: The technique can be miniaturised into portable kits for on‑site testing of food products, milk and water samples, offering rapid and cost‑effective screening.
Health impacts of Rhodamine B
- Toxicity: Animal studies link Rhodamine B exposure to DNA damage, cell mutations and tumours. Even low doses can have carcinogenic effects over time.
- Regulatory status: Because of its toxicity, Rhodamine B is banned in food, restricted in cosmetics and must be handled with caution in research labs.
Conclusion
The new coffee‑stain technique provides a promising tool for detecting banned dyes like Rhodamine B at very low levels. By combining nanotechnology with simple drying effects, scientists can create portable sensors that enhance food safety and protect public health.
Source: Business Standard · Oncology resource