Fabrication and characterization of rhodamine 6G entrapped sol–gel film test strip for virtually specific and sensitive sensing of nitrite

A test strip sensor was developed for nitrite by the entrapment of rhodamine 6G in sol–gel film. Evidence for successful fabrication of the test strip is provided by characterizations using UV–visible spectrophotometry (UV–vis), spectrofluorimetry, surface area analysis and scanning electron microscopy (SEM). The pink coloured sol–gel films turns orange on treatment with nitrite containing samples, acidified with sulphuric acid. Linear calibration graph (R2 = 0.9980) for nitrite was obtained in the range 40–120 ppb with a limit of detection of 7 ppb and this method is by far the most selective amongst the existing ones. The test strip also showed a reproducible result with RSD of 6% for 40 ppb of nitrite with response time of 10 min and 95% confidence limit for determinations of 40 ± 2 ppb of nitrite. A possible sensing mechanism is also proposed. The method was applied for the determination of nitrite in different types of environmental samples and the results obtained were in good correlation with those obtained by a standard method.