Study Of Synchronous Fluorescence Spectrometry In The Determination Of Pharmaceutical And Its Application

The spectrofluorimetric method has been widely used in quantitative analysis because of its highly sensitivity, selectivity and reproducibility as well as its relatively low cost. However, problems of selectivity can occur in multicomponent analysis because of the overlap of the broadband spectra observed. Synchronous fluorescence spectroscopy has been found to have several advantages such as simple spectra, high selectivity and low interference etc. Because of its sharp, narrow spectrum, synchronous fluorescence spectroscopy serves as a very simple, effective method of obtaining data for quantitative determination in a single measurement. In addition, the combination of synchronous fluorimetry and derivatives is more advantageous than conventional spectrofluorimetry in terms of sensitivity, especially when applied to the determination of multi-component analysis.According to the scanning modes of monochromators, synchronous fluorescence spectroscopy is classified into constant-wavelength, constant-energy, variable-angle and matrix isopotential. At present, the constant-wavelength method is used most extensively.This thesis consists of a review and two research sections. The review describes the principle, speciality of the normal fluorescence spectra and synchronous fluorescence, and the application of constant-wavelength synchronous fluorescence spectrometry in drugs analysis in recent 10 years. The second section is focused on the study of highly sensitive synchronous fluorescence spectrometry for determination of some medicines. Firstly, in review of normal fluorescence spectra of human urine and many drugs, the spectra are greatly overlapping, such problem was resolved by using synchronous fluorometry. On the basis of this, piroxicam and clebopride have been determined by synchronous fluorometric method which shows good analytical results without any pre-separation steps. Secondly, based on the nature fluorescence of drugs, novel synchronous fluorometric methods have been developed for the simultaneous analysis of propranolol hydrochloride and flunarizine hydrochloride, bendazol and flunarizine hydrochloride, respectively. Finally, meloxicam and levodopa can react with Ce(IV) to produce stong fluorescent species, According to this, new fluorescence methods for determination of meloxicam and levodopa were established.In conclusion, the proposed methods have the advantages of simplicity, rapidity, precision and sensitivity. The main contents are as follows:1 A novel synchronous ?uorimetry method for the determination of piroxicam in human urine was described. The experiments indicate that piroxicam has little fluorescence, but the fluorescence intensity of system could be sensitized dramatically by reaction with oxidation after acidic degradation. The results show that piroxicam could be oxidized by potassium permanganate in polyphosphoric acid to yield strong fluorescent species. The combination of synchronous fluorescence atΔλof 70nm and first derivative technique provides good analytical results and permits the direct determination piroxicam in human urine. The fluorescence intensity of system was linearly proportional to the concentration of piroxicam in the concentration range of 4.0×10^-92.4×10^-6g/mL and the detection limit of 3.8×10^-9g/mL.2 A rapid, simple, accurate and selective synchronous ?uorimetry method for the determination of clebopride in human urine was described. The experiments indicate that clebopride has endogenous fluorophore, and the fluorescence intensity was enhanced remarkably when formaldehyde was added into the system. The maximum emission wavelengths of clebopride and the urine blank were at 358.0nm and 414.0nm, respectively. Because the emission spectra of clebopride and fluorescent substance of human urine were overlapped partially, clebopride could not be determined directly by normal fluorimetric method. In order to solve this problem, the synchronous spectrum, maintaining a constant difference ofΔλ=30nm between the emission and excitation wavelengths in Britton-Robinson buffer solution (pH 6.60), was selected as optimum to perform the determination. The background interference of human urine was eliminated effectively. Under the optimum conditions, the fluorescence intensity was linearly proportional to the concentration of clebopride in the range of 2.8×10^-54.0×10^-3g/L. The detection limit was 1.1×10^-5g/L. The proposed method has been applied to the determination of clebopride in human urines samples with the recoveries of 95.0¹03.8%.3 A direct method for the simultaneous determination of propranolol hydrochloride and flunarizine hydrochloride using synchronous fluorimetry was described. The maximum emission wavelengths of propranolol hydrochloride and flunarizine hydrochloride were at 354 and 320nm, respectively. Because the emission spectra of two drugs were overlapped partially, propanolol hydrochloride and flunarizine hydrochloride could not be determined directly by normal fluorimetric method. However, the synchronous fluorimetry could be used for determining both drugs simultaneously without separation procedure. The method involved measuring the natural fluorescence of these drugs atΔλ=50nm in the media of acetate buffer solution. The synchronous fluorescence concentration plots were rectilinear over range of 1.2×10^-62.8×10^-3g/L and 2.0×10^-53.6×10^-3g/L for propranolol hydrochloride and flunarizine hydrochloride, respectively with lower detection limits of 3.2×10^-7 and 6.8×10^-6g/L.4 Simple and sensitive second derivative synchronous fluorometric method was developed for the simultaneous determination of bendazol and flunarizine hydrochloride. The method was based upon measuring the synchronous fluorescence of both the studied drugs in Britton-Robinson buffer of pH 3.29 atΔλ=100nm. The peak amplitude was measured at 278nm (-) and 232nm(+) for bendazol and flunarizine hydrochloride, respectively. With the application of second-order synchronous fluorimetry advantage, the proposed method could be utilized for a simultaneous direct concentration determination of bendazol and flunarizine hydrochloride without pretreatment step. The different experimental parameters affecting the native fluorescence of the studied drugs were carefully studied and optimized. The synchronous fluorescence concentration plots were rectilinear over range of 1.2×10^-5～3.6×10^-3g/L and 1.2×10^-4～6.8×10^-3g/L for bendazol and flunarizine hydrochloride, respectively with lower detection limits of 4.3×10^-6g/L and 1.0×10^-4g/L.5 A novel and sensitive spectrofluorimetric method for the determination of meloxicam has been developed. The experiments indicated that meloxicam has little fluorescence signal by itself, but it could reduce cerium(IV) to cerium(III). Cerium(III) could emit characteristic fluorescence atλex=260nm andλem=362nm in sulfuric acid medium. Whenβ-cyclodextrin (β-CD) was added into the system, the fluorescence intensity could be enhanced greatly. Based on this meloxicam-cerium(IV)-β-CD fluorescence system, a new fluorescent method was established for the indirect determination of meloxicam. Under optimal experimental conditions, the linear range was 8.0×10^-103.2×10^-7g/mL, the detection limit was 3.5×10ˉ10g/mL. It has been used for the determination of meloxicam in tablets and human urines with satisfactory results.6 The fluorescence characteristic of levodopa with cerium(IV) in alkalic medium has been studied. The experiments show that levodopa had endogenous fluorophore, but the fluorescence signal was weaker. The fluorescence intensity could be sensitized strongly by the reaction with cerium(IV) in the buffer solution of Britton-Robinson with pH 9.15. Based on this, a new simple, rapid and sensitive fluorescence method for the determination of levodopa has been developed. The linear relationship of fluorescence intensity and levodopa concentration was in the range of 0.08³.6μg/mL. The detection limit was 0.018μg/mL.