Lanthanide-DNA probe for spectrofluorimetric determination of some 6-fluoroquinolones in eye-ear pharmaceutical preparations

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© 2019 Elsevier B.V. A sensitive, accurate and precise spectrofluorimetric method was established for the quantification of ciprofloxacin HCl and norfloxacin drugs. The spectrofluorimetric method has involved the development of a ternary complex between the investigated drugs and Tb3+ in presence of Calf thymus DNA which was used as a fluorescence enhancing agent causing reduction in the non-radiative energy loss produced by O[sbnd]H vibration of H2O in the original Tb3+–drug complex. Thus, the fluorescence of the system (Tb3+–drug–DNA) at ʎem of 545 nm for ʎex of 272 nm was enhanced. Investigation of all the conditions that could affect the reaction as well as the formed complexes' spectral properties was performed. Upon utilization of the optimum reaction conditions; the spectrofluorimetric method was highly sensitive and showed linearity over the concentration range of 40–700 ng/mL for both ciprofloxacin and norfloxacin with a correlation coefficient of 0.9998 and 0.9997, respectively. The limit of detection was 12.56 ng/mL and 11.44 ng/mL, while the limit of quantification was 38.06 ng/mL and 34.66 ng/mL for ciprofloxacin and norfloxacin, respectively. The developed method was effectively utilized for the estimation of the studied drugs in eye-ear pharmaceutical dosage forms. The achieved results were compared statistically with those of the pharmacopoeial method where no significant difference was perceived concerning both accuracy and precision.

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