Analytical Chemistry

(Chris Devlin) #1

fused aromatic systems, cf. biphenyl and fluorene (Figure 9.11(b)). Structures containing heteroatoms or
which are ionized may undergo rapid relaxation by intersystem crossing thereby reducing or inhibiting
fluorescence, e.g. pyridine, nitrobenzene and iodobenzene exhibit no fluorescence whereas aniline,
phenol and chlorobenzene all fluoresce.


Some examples of fluorescing species and their analytical uses are included in Table 9.5.


Table 9.5 Applications of quantitative visible and ultraviolet spectrometry
Element or compound determined Reagent Example of application
Absorptiometry
Fe o-phenanthroline natural waters, petroleum products
Cu neocuproine minerals, alloys
Mn oxidation to steels

Cr diphenylcarbazide alloys, minerals
Hg, Pb dithizone food products, fish

reduction to molybdenum blue fertilizer residues, soils
aspirin — analgesic preparations
cholesterol Liebermann–Burchard reaction body fluids
sulphonamides diazo derivatives drug preparations
DDT nitrated derivative soils, fish
Element or compound determined Fluorescent emission maximum
(nm)

Example of application

Fluorimetry
vitamin A 500 nm foodstuffs, vitamin tablets
LSD > 430 nm body fluids

amphetamine codeine, morphine
drug preparations and body fluids

PAH 320 – 550 nm environmental samples
amines and amino acids as
derivatized by ninhydrin, o-
phthaldehyde (OPA), dansyl
chloride or fluorescamine

440 – 550 nm pre-^ or post-column derivatization for HPLC
separations

Al as alizarin garnet red complex 580 nm water samples and soils

Cd as 2-(o-hydroxyphenyl) –
benzoxazole complex

— water samples and soils

B as benzoin complex 450 nm water samples and soils
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