Dear collegues . I am working to determnate nitrite in Salvia officinalis and Lavender. with Iso 6634-1984. In one of the samples i have difficultiues because the colour doesnt develop. That is somethink that inhibit the the appareance of the rose colour.In the others samples with lower concentration of the nitrite the colour is developed very good., in this samples with highter concentration the colour is disguise. I have applied the ISO 6634-1984 . Is there anybody that works in this field that can help my understanding this problem?