Brazilian Journal of Analytical Chemistry - BRJAC - Brazilian Journal ...

determination o f C i p ro f l o x aC i n by s y n C h ro n o u s s C a n n i n g r o o m-temperature phosphorimetry
mum room-temperature phosphorescence of ciprofloxacin
induced by Th (IV) and induced by Cd (II) whose spectra
are indicated in Figure 4.
fi g u rE 4. Ci P r o f l o x a C i n r o o m-t E m P E ra t u rE PhosPhorEsCEnCE ExCitation
a n d Emission sPECtra in CEllulosE suBstratEs u n d E r t h E oPtimizEd C o n d it
i o n s u s i n g (a) CdCl 2 a n d (B) th(no 3 ) 4 .
3.3 ev a l u a t I o n o f I n t e r f e re n c e s f r o m m o x If l o x a c In a n d
g a t I f l o x a c I n In th e cIp r o f l o x a c In ph o s p h o re s c e n c e
An interference study was performed in order to evaluate
the influence of increasing concentrations of gatifloxacin
and moxifloxacin on the ciprofloxacin phosphorescence
induced by either Th(NO 3 ) 4 or CdCl 2 . In order to perform
such evaluation, phosphorescence from ciprofloxacin
(I CIP ) was compared to the ones observed from synthetic
mixtures containing ciprofloxacin and increasing concentrations
of either one of the other two fluorquinolones
(I (CIP + GAT) or I (CIP + MOX) ). Results in Table III indicate that
Parameter
when using Th (IV) and synchronous scanning with ∆λ
= 237 nm, the selective determination of ciprofloxacin
can be performed in samples containing either gatifloxacin
or moxifloxacin if the molar proportion of them does
not exceed two times the one of ciprofloxacin. For the
other mixtures, severe non-spectral interferences were
found as indicated by the I CIP /I (CIP + GAT) and I CIP /I (CIP + MOX)
values higher than the unit. However, such non-spectral
type of interference may be promptly corrected by using
analyte addition technique. In contrast, using Cd (II)
and synchronous scanning with ∆λ = 170 nm, non spectral
interferences are found even in samples containing
equimolar quantities of ciprofloxacin and the interferent
fluorquinolone (gatifloxacin or moxifloxacin).
Since up to 30% of the ingested quantity of fluorquinolones
is eliminated in urine in the original form,
a study to evaluate the potential detection of ciprofloxacin
in urine was performed. The results indicated
that urine matrix imposes non-spectral interferences
on the phosphorescence signal of ciprofloxacin, therefore,
cleaning up procedures to reduce protein content
of the biological sample were applied (protein
precipitation with methanol or ammonium sulfate),
however, such approaches did not solve the interference
problem. Interferences were promptly minimized
a ten-fold dilution of the sample using acetone/water
solvent system. The dilution of the sample is in part
compensated by the good detectability of the method.
Potential interferences from ciprofloxacin metabolites
were not evaluated due to the lack of standards.
3.4. an a l y t I c a l fI g u r e s of me r It
The analytical figures of merit for ciprofloxacin were
obtained under the experimental conditions optimized
indicated in Table II. In the presence of Th (IV) as phosphorescence
heavy atom inducer, the absolute limit of
detection (ALOD) of 9.6 ng was calculated while the
absolute limit of quantification (ALOQ) was 31.7 ng.
Using Cd (II) as the heavy atom inducer, the ALOD and
ALOQ were respectively 7.1 and 23.6 ng. ALOD and
ALOQ were calculated based on the following equations:
3s b m -1 V MM and 10s b m -1 V MM, where s b is
taBlE ii. oPtimizEd C o n d i t i o n s f o r thE d E t E r m i n a t i o n o f C iP ro f l o x a C i n u s i n g ssrtP.
CdCl 2
282\452 nm
Heavy atom salt
λ exc \λ em
Th(NO 3 ) 4
288\525 nm
∆λ 170 nm 247 nm
Buffer pH 10 Non buffered
Mass of salt on substratum 460 µg 600 µg
Mass of SDS on substratum 360 µg 360 µg
128 Br J Anal Chem