Differential Pulse Polarographic Study of Amoxicillin and Ciprofloxacin and its Determination in Pharmaceuticals

Keywords

Amoxicillin; Ciprofloxacin; DPP; Analysis.

Introduction

Antibiotics are a substance inhibits or kills the growth of bacteria [1] and belongs to a broader range of anti-vehicle microbiology group, used to treat infections caused by micro, including fungi and parasites organisms. The term "antibiotic" drafted by Waxman in 1942 to describe any substance produced by microorganisms counteracts the growth of other micro-organisms. Amoxicillin is an antibiotic of the penicillin group, it is one of the most commonly used antibiotics, addresses many of the bacterial infections by turning off the disease-causing bacteria growth, Figure below [2,3].

Several methods were use for the determination of amoxicillin in tablets or urine includes spectrophotometic [4-6], chromatography [7,8], LC/MS [9] and electrochemical methods [10]. Most of the reported methods undergo disadvantages, such as difficult procedure and expensive instruments requirement and low detection sensitivity.

Ciprofloxacin is antibacterial belongs to a family of largely effectual spectrum florokonyolon against the most Gram-negative and positive and is also effective against anaerobic bacteria and prevents the reproduction of DNA bacterial, Figure below [11,12].

A simple DPP method for the determination of ciprofloxacin hydrochloride and Tinidazole from tablets has been developed, these components produced waves at- 1.30 V and -0.38 V respectively in a solution of pH 6.5 [13].

Ciprofloxacin was determined individually by non-aqueous titration [14], UV-spectrophotometry and colorimetry [15-18], HPLC [19-24], capillary zone electrophoresis [25] Fluorescence Spectrodensitometry [26].

The purposes of this study were suggested and develop a simple and sensitive method for the qualitative and quantitative determination of amoxicillin and ciprofloxacin antibiotics in pure state and in commercial pharmaceuticals.

Materials and Methods

Apparatus

All measurements were conducted in a way differential pulse Polarographic, Using Polarography device 797VA Computrace-Metrohm, Herisau, Switzerland, The electrode assembly consist of the dropping mercury electrode, DME as working electrode, Ag/AgCl as reference electrode and a platinum auxiliary electrode, pH meter, four digit sensitive balance, Water bath, electric heater, Micropipette, Nitrogen gas with 99.999% purity, Glassware varied, Thermometer.

Materials

All the material and solvents used of high-purity (A.R. grade) purchased and obtained from Fluka and BDH and no further purification was need, water employed was de-ionized water, a standard samples for amoxicillin and ciprofloxacin supplied from in of Samarra drugs industries (SDI), Iraq, amoxicillin as Pulmoxyl, 500 mg and ciprofloxacin, 500mg commercially available from Julfar and ROX pharma Companies.

Preparation of samples

A 500 μg. ml-1 concentration standard solution of amoxicillin and ciprofloxacin drugs was prepared by dissolving the exact 25 mg weight of standard material in 50 ml water. Amoxicillin and ciprofloxacin in commercial pharmaceutical was also prepared as 500 μg. ml-1 concentrations based on the initial concentration of theirs active ingredient.

Analysis

Amoxicillin showed two peaks, the first one at applied potential -0.83V and the other at -0.25V, Figure-1, while the ciprofloxacin appears only one peak at the applied potential -1.41V, Figure-2 at the optimal experimental conditions. A 1–10.5 ml volume of the amoxicillin or ciprofloxacin solutions were analysis using Polarography device 797VA Computrace- Metrohm under the optimal experimental conditions found during this work. A standard calibration graph for amoxicillin and ciprofloxacin (Figure 3 and 4) in the concentration range 0.05 to 0.525 μg. ml-1 were prepared using the Method of Least Squares, M.L.S [27], and used to determine the amounts of amoxicillin or ciprofloxacin.

The regression equation was utilized for the calculation of unknown concentration in pharmaceuticals samples. The validity of the regression equation was testing by analysis laboratory made samples. Beers law was valid within the concentration range of amoxicillin or ciprofloxacin calculate.

General polarographic procedure

An a volume of amoxicillin or ciprofloxacin was transferred to a polarographic cell and diluted with de-ionized water, 2 ml of Britton-Robinson buffer was added at pH 7 for amoxicillin and pH 4 for ciprofloxacin with 0.5 ml of KCl as supporting electrolyte, the final cell volume with all other additions was equal to 20 ml, degassed with high purity nitrogen for 5 minutes to purge the oxygen. The polarograms were recorded at least twice from –0.0 to –1.8 mV and the mg amoxicillin or ciprofloxacin in the sample solutions were calculated from calibration plots.

Results and Discussion

The results show that the optimal analysis conditions for amoxicillin and ciprofloxacin was; the water as a best solvent at neutral medium, pH 7, while for ciprofloxacin was at acidic medium, pH 4, with Briton- Robinson buffer solution and 3M KCl as a supporting electrolyte also 4mm3 mercury drop size at 25°C. Tables 1 and 2.

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Table 1:

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Table 1.Optimal analytical conditions for Amoxicillin analysis.

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Table 2:

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Table 2. Optimal analytical conditions for ciprofloxacin analysis.

Amoxicillin showed two peaks, the first one at -0.83V while the second at -0.25V, Figure 1. It can be suggested a mechanism for the electrochemical reduction for those two peaks which show the reduction of carbonyl groups to hydroxyl, Figure 5.

While the ciprofloxacin appears only one peak at the applied potential -1.41V at the optimal conditions, Figure 2, this peak may be return to the reduction of the lone carbonyl to hydroxyl group, Figure 6.

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Figure1:

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Figure 1. Amoxicillin polarogram at special concentrations.

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Figure2:

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Figure 2. Ciprofloxacin polarogram at special concentrations.

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Figure3:

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Figure 3. Standard calibration graph for amoxicillin.

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Figure 4. Standard calibration graph for ciprofloxacin.

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Figure5:

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Figure 5. Suggested reduction mechanism for Amoxicillin reduction.

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Figure 6. Suggested reduction mechanism for ciprofloxacin.

Number of transferred electrons and the value of E½ (or Ep)

The actual number of transferred electrons in a reversible electrode process and the actual value of E½ (or Ep) was calculated using Heyrovsky–Ilkovic equation which explains the cathodes reduction wave as reversible process at 25°C [28].

This equation defines the relationship between diffusion current and applied potential for a reversible reaction involving the formation of a soluble product. Number of electrons (n) can be establish from the plot of log (i/id-i) against applied voltage (E) at set species concentrations. For a reversible process, (n) appear to be a correct number, whereas, an incomplete number for (n) represented an irreversible process. Number of required (n) for the reduction of amoxicillin and ciprofloxacin was calculated. A straight line obtained demonstrated the amoxicillin results, the actual first peak voltage Ep was -0.832V and 2 electrons was used whereas the second peak voltage Ep was -0.249V with 1 electron used, while the ciprofloxacin straight line obtained shows the actual peak voltage Ep was -1.38 V with 2 electrons required for the reduction, Figures -7, 8 and 9.

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Figure 7. Effect of E on the log i/id- i variation using Heyrovsky-Ilkovic equation at 3μg.ml-1 amoxicillin concentration, P1.

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Figure 8. Effect of E on the log i/id- i variation using Heyrovsky-Ilkovic equation at 3μg.ml-1 amoxicillin concentration, P2.

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Figure 9. Effect of E on the log i/id- i variation using Heyrovsky-Ilkovic equation at 3μg.ml-1 ciprofloxacin concentration.

Limit of detection and limit of quantification

The Limit of detection (LOD) and limit of quantification (LOQ) for the amoxicillin and ciprofloxacin was calculated using signal to noise ratio (S/N) of 3.3 and 10 respectively [27], it was found equal to 0.04 and 0.12 μg. ml-1 for amoxicillin and 0.02 and 0.06, μg. ml-1 for ciprofloxacin respectively.

Accuracy and Precision

The accuracy and precision of the method for the determination of amoxicillin and ciprofloxacin was tested. A 60 μg.ml-1 synthetic amoxicillin and ciprofloxacin samples was prepared and analysis, the results shows absolute errors between -0.02 to 0.08 and relative errors ranging from -0.03 to 0.13 % with 0.08 SD and %RSD not exceed ± 0.13 for amoxicillin, Table-3.

While ciprofloxacin analysis results shows absolute errors between -0.04 to 0.03 and relative errors within the range of - 0.07 to 0.05% with 0.26 SD and %RSD no more than 0.4, Table-4.

The developed DPP method was utilized for the determination of amoxicillin and ciprofloxacin in commercial pharmaceuticals, the results shows that the actual amoxicillin amounts in pulmoxyl capsules, 500mg in the range 498.1 – 498.7 mg which is actually equal to the amount installed in the original product, where’s ciprofloxacin amounts in ciprofloxacin 500 drug, shows their amounts between 488.72 – 489.83 mg which is negligible less than the amount installed in the original product, Tables-5 and 6.

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Table 3:

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Table 3. Analysis of synthetic made amoxicillin sample.

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Table 4:

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Table 4. Analysis of synthetic made ciprofloxacin sample.

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Table 5:

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Table 5. Analysis of commercial pharmaceuticals amoxicillin.

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Table 6. Analysis of commercial pharmaceuticals ciprofloxacin.

Conclusion

In the practical applications of this method several advantage found, first; using DPP which give sensitive and selective determination of these antibiotics, second, the developed methods proved to be rapid since the analysis of each sample required few minutes.