Downward peaks

[HW Mueller]

Peeking in from vacation:
Srinivas, what´s a UV quencher?

[Srinivas SK]

UV-quenching is used widely in TLC, to detect compounds that do not fluoresce under UV. Done with a fluorescent TLC plate containing small amounts of fluorescein. Under UV , a UV quenching compound would show up as a dark band against a fluorescent green background. Such a compound may show up as a negative peak in an HPLC analysis with UV detection.