Trace analysis by molecular spectroscopy.
This thesis describes new analytical methods for trace or ultra-trace
analysis by molecular absorption and emission spectroscopy. The initial
part of the thesis is devoted to an introduction to molecular
electromagnetic absorption spectroscopy and molecular fluorescence.
The principles, advantages and limitations of spectrophotometric and
fluorimetric measurement are discussed. The concepts of enzymes and
their applications in analytical chemistry are also expounded.
Two organic compounds, 5-( 4-arsonophenylazo )-8-(p-toluenesulfonamido)quinoline
(APTSQ) and 5-(p-methoxyphenylazo)-8-(p-toluenesulfonamido)
quinoline (MPTSQ), have been synthesised and used as new
chromogenic anellor f1uorogenic reagents. Five specific, highly sensitive,
simple, precise and inexpensive novel analytical methods have been
(1) A spectrophotometric method is described for the determination of
cobalt. The maximum absorbance is at 582 nm with a molar absorptivity of
1.18 x 1 as I mor' cm-1
. Beer's law is obeyed for cobalt concentrations in the
range 0-0.5 J.l.g mr'.
(2) A fluorimetric method for the determination of cobalt is proposed.
The fluorescence intensity is measured at Aex 287 nm and Aem 376 nm.
The response is linear up to 25 ng mr' and the detection limit is 0.002 ng
mr'. The mechanism of the fluorescence reaction has been investigated.
(3) A flu~ri~etric method is proposed for the d~ter~i~~tion of H202.
The response IS linear up to 12.2 ng mr H:t>2. The detection limit IS 0.16 ng mr'.
(4) An enzymatic assay for glucose by spectrofluorimetry is described.
The fluorescence intensity is proportional to the concentration of glucose
up t0180 ng mr'. A detection limit of 5.4 ng mr' was obtained and allowed
the determination of glucose in an extremely small amount of serum
(O.5J.1.I) and urine (1 J.l.1).
(5) A fluorimetric method for the determination of iron is proposed,
based on the reaction between iron(III) and MPTSQ in the presence of
cetyltrimethylammonium bromide. The fluorescence intenSity (Aex=317
nm, A.em=534 nm) is linear up to 170 ng mr' with a detection limit of 0.12
n9 mr'. An investigation of the mechanism of the fluorescence reaction
has been made.
The applications of the proposed methods for the determination of the
concerned analytes at low levels in biological, environmental,
pharmaceutical or beverage samples are also reported.