Voltammetric behavior of erythromycin ethylsuccinate at a renewable silver-amalgam film electrode and its determination in urine and in a pharmaceutical preparation

Abstract

Voltammetric behavior of erythromycin ethylsuccinate at a renewable silver-amalgam film electrode and its determination in urine and in a pharmaceutical preparation, Electrochimica Acta http://dx.2 Graphical abstract 3 Highlights  Voltammetric characterization of erythromycin ethylsuccinate (EES) on Hg(Ag)FE  Trace level determination of EES by electroreduction based SWV and SW-AdSV methods  Protonation of the tertiary amino group supports the adsorption of EES on Hg(Ag)FE  1 H NMR confirms chemical shifting of tertiary amine methyl proton signals with pH  Comparative HPLC-DAD measurements were performed for the validation of the methods 4 AbstractErythromycin, a macrolide antibiotic, has similar antimicrobial spectrum to penicillin and it is widely used, especially in the treatment of patients who are allergic to penicillin.In this work, the application of a renewable silver-amalgam film electrode (Hg (Ag)FE) for the characterization and determination of erythromycin ethylsuccinate (EES), a widely used esterified form of this antibiotic, by means of cyclic voltammetry (CV) and square wave voltammetry (SWV) is presented. In the aqueous Britton-Robinson buffer (pH 5.0-9.0) that served as the supporting electrolyte, one reduction peak of EES was observed in the investigated potential range between -0.75 V and -1.80 V vs SCE, with peak potential maxima ranging from -1.59 V to -1.70 V, which strongly depended on the applied pH, as did the peak shape. For the analytical purposes the pH of 7.0 was selected, since in this electrolyte the EES peak was well-shaped and separated from the background current of the supporting electrolyte in both cases; in the direct cathodic SWV and in the case of square wave adsorptive stripping voltammetry (SW-AdSV). It was established, by the Ep-pH correlation, that protons strongly influenced the electrochemical reduction of EES. The CVs recorded between 0.025 -0.50 V s -1 at pH 7.0 confirmed that the electrode reaction is adsorption-controlled. Based on the series of 1 H NMR measurements it is proved that the tertiary amino group of EES is mainly in its protonated form at pH 7.0 which may lead, at appropriate accumulation potential and time, to the favored adsorption of the target ionic form of the analyte improving on such way the sensitivity of the SW-AdSV method.The optimized procedures resulted in stable SWV responses with good linear correlation in the EES concentration range from 4.53 to 29.8 µg mL -1 (LOD = 1.36 µg mL -1 ), and from 0.69 µg mL -1 to 2.44 µg mL -1 (LOD 0.21 µg mL -1 ) in the case of optimized SWAdSV. The relative standard deviation is below 1.5%. The reliability of the elaborated procedures and thus the accuracy of the obtained results were validated by comparing them with those obtained by means of HPLC-DAD measurements. The direct cathodic SWV method was successfully applied for the determination of EES in the pharmaceutical preparation Eritromicin ® , while SW-AdSV was applied in the case of the spiked urine sample.In both cases, the standard addition meth...

Voltammetric behavior and determination of the macrolide antibiotics azithromycin, clarithromycin and roxithromycin at a renewable silver – amalgam film electrode

“…Before use, the surface of the Hg(Ag)FE was chemically cleaned in a 2% HNO 3 solution for about 5 min and then covered with a new amalgam film by immersing it in the internal amalgam pool of the electrode [47,48]. The Hg(Ag)FE required electrochemical activation before initial measurements in the chosen supporting electrolyte by cycling the potential in the range from À0.20 to À1.60 V over the course of around 20 cycles [35,41,47]. Furthermore, in every set of measurements, subsequent voltammetric curves were recorded for a renewed electrode surface, which was achieved by simply dipping the silver amalgam wire into the amalgam pool.…”

“…As a follow-up to the afore-mentioned research related to EES [35], in the presented work the voltammetric behavior of AZI, ROX and CLA at the Hg(Ag)FE was investigated by means of optimized direct square wave voltammetric (SWV) and cyclic voltammetric (CV) measurements. The influence of the pH of the supporting electrolyte on the generation of the reduction signals in the case of all three macrolides was studied in the pH range from 4.0 to 11.9.…”

“…The ability to easily and quickly refresh the electrode surface before each measurement allows the Hg(Ag)FE to be applied in adsorptive stripping measurements [39], as in the case of EES [35], doxorubicin [41], closantel [42] and chlornitrofen [54]. When considering the structure of EES and its affinity to the Hg (Ag)FE under optimized measurement conditions [35] and the three semi-synthetic macrolide antibiotic target analytes, it can be noted that -beside of different possible electroactive centers -all of them are amines, with pK a values between 8.1 and 9.5 (for more details see Table 1) [55][56][57][58][59][60][61][62][63][64][65][66][67][68].…”

“…Recently, a renewable silver-amalgam film electrode (Hg(Ag)FE) was applied to study the reduction of EES, the analytical signal of which appeared in a fairly negative potential range, and a trace-level adsorptive stripping voltammetric method was used to determine its concentration in a selected pharmaceutical preparation and in a spiked urine sample [35]. It is well-known that the Hg(Ag)FE is a relatively new type of amalgam-based electrodes [36][37][38][39], and provides an alternative to the hanging mercury drop electrode due to their similar electrochemical characteristics [40]; the Hg(Ag)FE enables the determination of a wide range of analytes, including different organic compounds [35,[41][42][43][44][45][46][47][48][49][50][51][52][53][54]. For example, it was used for the determination of the levels of some medications, such as EES [35], doxorubicin [41], closantel [42], moroxydine [43], ambazone [44], proguanil [45], prednisolone [46] in spiked urine samples [35,41,[43][44][45] and in pharmaceutical preparation [35,42,[44][45][46].…”

“…Voltammetric measurements are suitable for the characterization and/or determination of selected macrolide antibiotics either in the case of their oxidation [26][27][28][29][30][31] or reduction [32][33][34][35]. As far as oxidation is concerned, one oxidative peak was recorded for AZI at a carbon paste electrode [26], glassy carbon electrode [27], and polycrystalline gold electrode; the behavior of CLA was similar in the case of the polycrystalline gold electrode [28].…”