Nondestructive with fluorescent reagents

Nitrous fiunes reagent 225, 226 Nondestructive detection 42 ff -with fluorescent reagents 44 -with iodine 46 -with pH-indicator 45 Noradrenaline 76, 240, 393 — 396 Norephedrine 76 Norfenefnne 76 Norfenfluramine derivatives 45 1 l-Nor-d -THC-9-carboxy lie acid 289,292 Novonal 339 Nucleosides 364... 

A detailed discussion of fluorescence quenching, fluorescence, and other non-destructive TLC detection methods such as the use of reagents giving reversible color reactions and various biological methods was published by Barrett (1974). Although visualization with UV light is nondestructive with most substances and, therefore, well suited for preparative purposes, rearrangement of structure can sometimes occur—for example, with some steroid and vitamin molecules. 

A number of useful chemical methods are available for detecting or quantifying lipid classes. In some cases, the specificity of the colours developed can be used to help with identifications. Also when a nondestructive fluorescent reagent is used, lipids can be quantitated on the plates by a scanning fluorimeter - though, because different lipids have different fluorescence values, calibration curves must be made. 

In Chapter 7, approaches for visualization of zones in chromatograms are discussed, including use of nondestructive and destructive dyeing reagents, fluorescence quenching on layers with a fluorescent indicator, and densitometry. In Chapter 8, additional detection methods, such as those used for biologically active and radioactive zones, as well as the recovery of separated, detected zones by scraping and elution techniques are covered. 

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