The formation of metal chelates with various ligands may lead to the production of fluorescent chelates or enhance the fluorescence of the chelating agent. This paper describes two sensitive, selective and computer-solved methods, namely, zero order (SF) and second-derivative synchronous spectrofluorimetry (SDSFS) for nano-quantitation of two carbapenems; meropenem (MP) and ertapenem (EP). The methods are based on the chelation of MP with Tb and EP with Zr in buffered organic medium at pH 4.0 to produce fluorescent chelates. In the zero order method, the relative synchronous fluorescence intensity is measured at 327.0 nm at Δλ = 70.0 and 100.0 nm for MP and EP, respectively. The second method utilizes a second-derivative technique to enhance the method selectivity and emphasize a stability-indicating approach. The peak amplitudes ( D) of the second-derivative synchronous spectra were estimated to be 333.06 and 330.06 nm for MP and EP, respectively. The proposed synchronous spectrofluorimetric methods were validated according to the International Conference on Harmonization (ICH) guidelines and applied successfully for the analysis of MP and EP in pure forms, pharmaceutical vials and in synthetic mixtures with different degradants of both drugs. Under optimum conditions, the mole-ratio method was applied and the co-ordination ratios of MP-Tb and EP-Zr chelates were found to be 1:1 and 1:3. The formation constants for the chelation complexes were evaluated using the Benesi-Hildebrand's equation; the free energy change (ΔG) was also calculated. The results indicated that EP-Zr was more stable than the MP-Tb chelate. Moreover, the developed methods were found to be selective and inexpensive for quantitative determination of both drugs in quality control laboratories at nano-levels.
An inexpensive stability−indicating anodic voltammetric method for rapid determination of two non‐classical β‐lactam antibiotics; Meropenem (MP) and Ertapenem (EP) has been developed and validated. The method was based on the enhancement of voltammetric response at a disposable graphite pencil electrode (GPE). Differential pulse voltammetric (DPV) method was developed for quantification of both drugs in B−R buffer solution (pH 2.0) at GPE. The GPE displayed very good voltammetric behavior with significant enhancement of the peak current compared to glassy carbon electrode (GCE). Stress stability studies were performed using 0.5 M of either HCl or NaOH and H2O2. Mass and infrared spectroscopy were used for identification of degradants and their pathways were illustrated. Under optimal conditions, the peak currents showed a linear dependence with drug concentrations. The achieved limits of detection (LOD) were 1.23, 2.07 and 1.50 μM for MP and two waves of EP, respectively. The developed voltammetric method was successfully applied for direct determination of MP and EP in drug substances, pharmaceutical vials and in presence of either their corresponding hydrolytic, oxidative‐degradants or interfering substances with no potential interferences. The differential pulse voltammograms were highly advantageous and applicable in QC laboratories for rapid, selective micro‐determination of MP and EP.
The present study concerns with investigation of the electrochemical activity of meropenem (MP) at ultra-trace graphite electrode (UTGE). The electrochemical measurements were performed in various buffer solutions in pH range (2.0-8.0). One irreversible anodic peak was observed in acidic medium. The effects of pH and scan rate on the peak current and potential were studied. The adsorption-controlled nature of MP peak was demonstrated. Therefore, it is directed to develop adsorptive stripping square wave voltammetric technique (AdS-SWV) for quantitative determination of MP in drug substance, pharmaceutical vials and in presence of interference substances. Under optimum experimental conditions, a linear dependence relationship was obtained over MP concentration range of 500.0-15000.0 nM. The limits of detection (LOD) and quantification (LOQ) were 160.0 and 470.0 nM respectively. Chemical safety is assessed at different aspects. Qualitative and quantitative metrics reveal excellent eco-friendly voltammetric method. In spite of high budget of UTGE; multiple merits of nano-sensitivity, selectivity, greenness evidence and high efficiency encourage wide application of our developed method in QC using UTGE in comparison to other chemically-modified electrodes.
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