Thread-based platform for nitrite detection based on a modified Griess assay

A new thread-based platform was developed for colorimetric detection of nitrite based on a modified Griess assay. Cellulose thread was functionalized with a p-aminobenzoyl group and impregnated with chromotropic acid as a coupling reagent. The reactions including diazotization and coupling reaction occurred along the length of the thread and a pink colored band was produced in the presence of nitrite. The band length was proportional to the nitrite concentration. The chemically modified thread allowed sequential sample introduction due to an abundant content of the starting reagent on the thread surface. As a result, this thread platform provided detection of low-level nitrite and ease of determination via length measurements. The platform could be used to detect nitrite in a range from 50 to 1,000 µM with the lowest detectable concentration of 50 µM. It was successfully used to detect nitrite in drinking water, runoff from a field, and sausage.