Use of Fluorescent Layers and Indicators

The indicators mentioned do not usually interfere with the quantitative evaluation after extraction. They are however dissolved to some extent by acid extraction agents and may then interfere in certain analytical methods of determination, e. g., polarography [489]. 

Spraying with solutions of organic fluorescent indicators or mixing such indicators into the adsorbent, is often impracticable. These substances are soluble in solvents of polarity appropriate for development and elution. They have however been used with success in exceptional cases. 

Thus lipid spots have been sprayed with rhodamine 6G solutions before gas chromatographic evaluation [475]. Steroids and insecticides [722] and oestrenols [217] could be localised before quantitative evaluation, on layers to which pyrene  

zinc silicate and zinc cadmium sulphide (Firm 108), calcium halophos-phate N 83 white, WQ, GQ or TQ (Firm 147) Ijeuchtstoff ZS-Super (Firm 118). 

Sodium salts of 3-hydroxypyrene-5,8,10-trisulphonic acid and of 3,5-dihydro-xyp3rrene-8,10-disulphonic acid (Firm 55). 

---