Use of other Colour Reagents

Other colour tests which do not interfere in the subsequent quantitative determination, can be of only limited application. An example is with organic phosphorus compoimds, where the substance can be ignited and determined through its phosphorus content [166, 258]. Glycolipoid fractions have been localised with ammoniacal bromothymol blue indicator and then, after extraction, evaluated with anthrone/sul-phuric acid [324]. 17-Hydroxycorticosteroids have been sprayed with blue tetrazolium and then determined with phenylhydrazine/sulphuric acid [11] the steroids partly reacted with the identification reagent which led to difficulties. 

If the separated yet colourless substances can be converted with suitable spray reagents into coloured compounds, these may perhaps be determined directly after elution by a photometric method the scope of this method is discussed on p. 154. 

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