A novel, simple, sensitive and selective spectrofluorimetric method was developed for the determination of trace amounts of chlorzoxazone and Ibuprofen in pharmaceutical tablets using optical sensor Eu-Tetracycline HCl doped in sol-gel matrix. The chlorzoxazone or Ibuprofen can remarkably enhance the luminescence intensity of Eu-Tetracycline HCl complex doped in a sol-gel matrix in dimethylformamide (DMF) at pH 9.7 and 6.3, respectively, λ(ex) = 400 nm. The enhancing of luminescence intensity peak of Eu-Tetracycline HCl complex at 617 nm is proportional to the concentration of chlorzoxazone or Ibuprofen a result that suggested profitable application as a simple optical sensor for chlorzoxazone or Ibuprofen assessment. The dynamic ranges found for the determination of chlorzoxazone and Ibuprofen concentration are 5 × 10(-9)-1 × 10(-4) and 1 × 10(-8)-7 × 10(-5) mol L(-1), and the limit of detection (LOD) and quantitation limit of detection (LOQ) are 3.1 × 10(-10), 9.6 × 10(-10) and 5.6 × 10(-10), 1.7 × 10(-9) mol L(-1), respectively.

A simple and sensitive spectrofluorimetric method for determination of trace amount of doxycycline hydrochloride (DC) in pharmaceutical tablets and serum samples was developed. In ammonia buffer solution of pH 8.9 the doxycycline hydrochloride can remarkably enhance the luminescence intensity of the Sm(3+) ion in Sm(3+)- DC complex at λ(ex)=400 nm. The produced luminescence intensity of Sm(3+)- DC complex in DMSO is in proportion to the concentration of DC and used as optical sensor for its determination. The dynamic range for the determination of DC is 1 × 10(-8)-5 × 10(-6) mol L(-1) and in case of quantum yield calculations is 7 × 10(-9)-5 × 10(-6) mol L(-1) with detection limit of 6.5 × 10(-10) mol L(-1). The enhancement mechanism of the luminescence intensity in the Sm(3+)- DC system has been also discussed. A comparison with other spectrofluorimetric methods for tetracycline derivatives in which Eu(3+) ion is used instead of Sm(3+) ion is also studied.

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