A new colorimetric test for detection of hydroxyl groups in solid-phase synthesis

A new colorimetric test (methyl red-DIC test) for monitoring the presence of hydroxyl groups on resins for use in solid-phase synthesis was developed. The resin became orange-red when the carboxyl group of methyl red formed ester linkages with the resin’s hydroxyl groups. This new test can be used not only for qualitative analysis but also quantitative analysis by using pictures of the relationship between color depth and hydroxy loading rates.