Cyclic voltammetry and differential pulse voltammetry were used to explore the adsorption behavior of three antibacterial agents at a carbon paste electrode. The drugs were accumulated on a carbon paste electrode, and a well-defined oxidation peak was obtained in acetate buffer (pH 5.0). The adsorptive stripping response was evaluated as a function of some variables such as the scan rate, pH and accumulation time. A simple, precise, inexpensive and sensitive voltammetric method has been developed for the determination of the cited drugs (Lomefloxacin (LFX), Sparfloxacin hydrochloride (SFX), and Gatifloxacin (GFX)). A linear calibration was obtained from 2 x 10(-7) M to 4 x 10(-5) M for LFX, 2 x 10(-7) M to 6 x 10(-5) M for SFX, and GFX. The limits of detection (LOD) were 4.2 x 10(-7), 7 x 10(-7) and 6.6 x 10(-7) M, while the limits of quantification (LOQ) were 1.4 x 10(-6), 2.3 x 10(-6) and 2.2 x 10(-6) M for LFX, SFX, and GFX, respectively. The R. S. D. of five measurements at the 1 x 10(-6) M level were 0.4, 0.5 and 0.3 for LFX, SFX and GFX, respectively. The method was applied to the determination of LFX, SFX and GFX in dilute urine samples and dosage forms, and compared with the HPLC method.
Nifuroxazide, 4-hydroxybenzoic acid [(5-nitro-2-(furanyl)methylene]hydrazide (I), is used for the treatment of acute and chronic diarrhea, gastroenteritis, and colitis. The analytical methods used for the determination of nifuroxazide in dosage form include titrimetric 1 , complexometric 2 , ultraviolet spectrophotometric 3 , and high-performance liquid chromatography (HPLC).
3The plasma and urinary concentrations of nifuroxazide after absorption of the drug from the gastrointestinal tract were determined by HPLC with UV detection. 4,5 The plasma concentration of nifuroxazide was detected at a level of <10 ng/ml after chronic administration of a dose of 800 mg/d. 5 At present, only a few studies dealing with nifuroxazide polarographic behavior have been reported, and the authors seems to have encountered only two waves. [6][7][8] In our earlier work, four polarographic waves for nifuroxazide were reported and ascribed to a subsequent reduction of the nitro group and reduction fission of the hydrazono group.
9The main challenge in developing a procedure for the measurement of any drug substances is high sensitivity coupled with applications to real samples. Adsorptive stripping voltammetry has been effectively used for the determination of nanomolar or subnanomolar levels of several drugs. [10][11][12] The present work is concerned with the trace quantification of nifuroxazide using differential-pulse cathodic stripping voltammetry. The adsorption of nifuroxazide onto a hanging mercury drop electrode can be used as an effective preconcentration step before a voltammetric measurement. In this way, a highly sensitive measurement of this drug at the low level (ng/ml) found in serum after therapeutic doses of nifuroxazide can be achieved. Such techniques for measurement of serum concentrations of nitrofurans are necessary in order to evaluate and avoid toxic concentrations of such drugs.
Experimental
ReagentsA stock solution (1×10 -4 M) of nifuroxazide (Lab. Roques, France) was freshly prepared in pure methanol and stored at 4˚C in the dark. A series of standard solutions was then prepared daily by dilution with methanol of the stock solution. Britton-Robinson, acetate and phosphate buffers were used as supporting electrolytes. All of the reagents used were of analytical-reagent grade. Deionized double distilled water was used throughout the work.
ApparatusA PAR polarographic analyzer (Model 264A) coupled with a PAR 303A static mercury drop electrode and a PAR305 stirrer were used. The voltammograms were recorded on an EG&G Princeton Applied Research (Model RE0091) X-Y recorder. All of the potentials were referred to a Ag/AgCl reference elec- Control and Research, P.O, 29 Cairo, Egypt The adsorption behavior of nifuroxazide on a hanging mercury drop electrode (HMDE) was critically examined using cyclic voltammetry and differential pulse techniques. The effect of different parameters on the accumulation behavior of the adsorbed species was tested. Thus, a sensitive stripping voltammetry procedure for the determina...
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