Safranin O: Lot Variation in Performance as a Diazonium Base

Abstract

The performance of safranin O (C.I. 50240) as a diazonium base was tested on 24 lots with Biological Stain Commission certification dates ranging from 1931 to 1972. In general, recently certified lots performed better than the oldest lots, but good performance was obtained with lots certified in 1951-52. Dye content specified for certification tests did not correlate with performance as a diazo. Differences in average performance of samples from the 4 suppliers showed less variation than the variation shown by individual lots from some of the suppliers; moreover, these variations did not show a close correlation attributable to the age of the sample. Spectroscopy revealed a smaller group with λ = 530-532 nm and a larger one at 534, but there was no consistent variation in average performance as a diazo reagent attributable to the absorption maxima.