Oxygen, solvents fluorescence detection

The mobile phase plays an important part in the fluorescence of a molecule. Unless chosen with care, the mobile phase can quench the fluorescence of the molecule of interest. Most of the non-halogen-containing solvents used in HPLC can be used with fluorescence detection. However, dissolved oxygen or other impurities in the eluent can cause quenching. The solvent polarity and the pH of the mobile phase can also affect the fluorescent process if they influence the charge status of the chromophore. For example, aniline fluoresces at pH 7 and at pH 12, but at pH 2, where it is cationic, it does not fluoresce. Table 3.5 shows wavelength selections for some common LC-fluorescence applications.30... 

A bubble in the detector s flow cell typically manifests itself as a spike which may hinder peak detection and integration. Dissolved oxygen poses special problems such as baseline shifts caused by the formation of ultraviolet (UV) absorbing 02-solvent complexes and diminished fluorescence response (quenching). 

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