Chemistry Reference
In-Depth Information
The combination of derivative and SFS was first suggested by John and Soutar [36] as a mean of improving
the selectivity of analytical methods. The advantages as well as the limitations of this method have been the
topic of several reports [37,38]. The applicability of derivative synchronous fluorescence has been shown in the
determination of mixtures [39-41], some of which could only be satisfactorily resolved by time-consuming or
expensive techniques. Recent development of this technique has been reviewed by Patra and Mishra [42].
Specificity is a particular problem in the determination of fluorescent drugs [43]. Derivative SFS
technique has been used to develop simple, rapid and sensitive spectrofluorimetric methods for the
simultaneous determination of drugs and nowadays this technique is the most widely used in pharmaceutical
analysis of several mixtures in their co-formulated dosage forms and biological fluids. Because of the need
to monitor the drug level in human fluids, a variety of methods was developed for the quantitative
estimation; these methods are not free from disadvantages [44]. The biochemical assays are faster, more
specific and generally more sensitive than microbiological techniques. However, they require the use of
radioactive isotopes and in addition, they require expensive reagents and sophisticated equipment. Several
chromatographic methods have been also reported for the assay of the drug. These methods offer a high
degree of specificity, but most of these are time consuming, requiring sample pretreatment prior to the
measurement, different internal standards, when applied to serum or urine, and the use of organic solvents.
These drawbacks, in addition to the instrumental limitations, preclude their use in routine clinical analysis
and in Green Analytical Chemistry.
The second-derivative constant-wavelength SFS technique is the most frequently used for the simultaneous
determination of drugs. The suitability of this technique has been widely shown since the 1980s, for example,
for the simultaneous determination of epinephrine and norepinephrine in urine, with analytical recovery
about 94
for norepinephrine [45]. First and second derivative SFS was employed
in the determination of the alkaloid berberine [46]. By using second-derivative SFS, the simple resolution of
the anti-coagulant rodenticides, warfarin and bromadiolone, in the presence of
%
for epinephrine and 91
%
-cyclodextrin was
accomplished through a differential effect on the fluorescence intensity of these compounds; mixtures of
warfarin and bromadiolone in the ratios 4:1 and 1:10 were satisfactorily resolved [47]. Also, the simultaneous
determination of nonsteroidal anti-inflammatory drugs [48] and of salicylic acid and its derivatives or its
metabolites in human serum [49,50], urine [51] and aspirin formulations [52] has been reported. Lianidou
et al
. [53] reported an improved spectrofluorimetric method for the simultaneous determination of diflunisal
and salicylic acid in serum and urine samples not requiring the use of organic solvents. The method was based
on the formation of ternary Tb-EDTA-Diflunisal and Tb-EDTA-salicylic acid complexes and second
derivative SFS technique, allowing the simultaneous determination in a single scan, and without removal of
proteins. In the last decade, second-derivative constant-wavelength SFS has been utilized for the determination
of different drugs mixtures in their co formulated dosage forms and biological fluids, such as oxytetracycline
in medical premixes and feeds [54], cinnarizine and domperidone in pharmaceutical preparations and
biological fluids [55], fluphenazine hydrochloride and nortriptyline hydrochloride in pharmaceutical
preparations [56], sulpiride and its alkaline degradation product [57].
This derivative technique has been also used to analyse mixture of several hydrocarbon compounds.
Lloyd [58], made evident the enhancement of relatively minor spectral features by second-derivative
synchronous fluorimetry comparing the results obtained for a motor oil by direct and derivative SFS.
Vo-Dinh [59] employed this technique to analyse a synthetic mixture of several aromatic compounds. Later,
it was applied to an extract from an atmospheric sample (collected in a workplace environment) which had
previously been analysed by direct synchronous fluorimetry [60]. The second-derivative peaks were narrower
than those found by direct synchronous scanning. Benzo(a)pyrene (in smoke-flavour agents) has also been
determined by second-derivative, constant-wavelength SFS [61]. Similar methods have been reported for the
determination of PAH pollutants in drinking water [62,63]: even in methods capable of determining 11 PAHs
[64] in a mixture of 18.
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