COMBINED USE OF IONIC LIQUID AND HYDROXYPROPYL-b-CYCLODEXTRIN FOR ENANTIOSEPARATION
413
of 10 model compounds. Following the addition of IL to BGE
containing HP-b-CD, the resolutions of all the analytes were im-
proved significantly. The possible mechanisms involved were
discussed and the results proved that there was a synergistic
effect between HP-b-CD and IL and that the cationic part of IL
played an important role in the increased resolution. Finally,
the developed method was validated and found to be sensitive
and efficient for enantiomeric purity determination of ofloxacin.
It allowed the determination of 0.2% R-ofloxacin in the presence
of a large amount of the S-form.
LITERATURE CITED
Fig. 3. Electropherograms of ofloxacin enantiomers (A: 0.2% R-ofloxacin in
S-ofloxacin standard solution; B: S-ofloxacin bulk samples) (BGE: 40 mM HP-
b-CD, 50 mM NaH2PO4-H3PO4, pH 2.75, and 30 mM [Emim][L-lactate]).
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10:1, respectively. The results for R-ofloxacin were deter-
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Precision and stability. Since the electropherogram of the
S-ofloxacin bulk sample did not show any R-enantiomer impu-
rity, a known quantity of the R-enantiomer (1.60 mg ꢁ ml–1) was
added to the S-ofloxacin bulk sample (800.00 mg ꢁ ml–1) to pre-
pare a simulated sample (corresponding to 0.2%) for validation
of the precision and stability. To validate the precision of
the proposed method, both repeatability and intermediate
precision were investigated. Repeatability was studied by
performing sequentially a series of six injections of simulated
samples. The RSD values were 1.8% and 4.2% for the migration
time and peak area, respectively. Intermediate precision was
determined by analyzing the simulated samples by repeating
the experiments on three successive days. The RSD values
were 4.2% and 5.4% for the migration time and peak area,
respectively. The RSD values for both repeatability and inter-
mediate precision were below the acceptable maximum value
of 10%, illustrating the good precision of the developed method.
The stability of the simulated sample was analyzed at 0 h, 2 h,
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was 4.1% (RSD) which proved that the R-ofloxacin solution
was stable over a 12 h period.
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Accuracy. Recovery tests were carried out to investigate the
accuracy of the proposed method by standard addition of a
reference (adding a known concentration of R-ofloxacin solu-
tion to the S-ofloxacin bulk sample solution to obtain a final
solution containing 1.60 mg ꢁ ml–1 R-ofloxacin, corresponding
to an impurity content of 0.2%). Six samples were prepared.
The recoveries of R-ofloxacin were 97.9, 97.2, 104.6, 105.5,
99.7, and 102.9 %, respectively, with an RSD value of 3.5%.
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The method was used to determine the amount of chiral impu-
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(Fig. 3B). The result was then compared with that of a standard
solution containing 800.00 mgꢁ ml–1 S-ofloxacin and 1.60 mgꢁ ml–1
R-ofloxacin (with an impurity content of 0.2%, Fig. 3A). It was
clear that the concentration of the chiral impurity in S-ofloxacin
bulk samples was well below 0.2%.
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CONCLUSION
A CE method employing a dual system of HP-b-CD and
[EMIm][L-lactate] has been developed for the enantioseparation
Chirality DOI 10.1002/chir