Recent Advances and Future Perspectives in Pharmaceutical Analysis

Enhancement of graphene oxide through β-cyclodextrin composite to sensitive analysis of an antidepressant: Sulpiride

In this study, the electrochemical behavior of sulpiride (SUL) was examined deeply by using pyrolytic graphite electrode modified with graphene oxide (GO) and β-cyclodextrin (β-CD). The developed nanosensor indicated considerable impact by significantly increasing the signal of SUL compared with the bare electrode. Cyclic voltammetry (CV), differential pulse voltammetry (DPV), and square wave voltammetry (SWV) methods were utilized to investigate the SUL electrochemical analysis in aqueous solutions. Under optimum experimental conditions, calibration plot for SUL with a limit of detection of 2.83 × 10−9 M was obtained at accumulation time of the 30 s using square wave adsorptive stripping voltammetric technique (AdSSWV) in the range of 1.0 × 10−7 to 5.0 × 10−5 M. The effects of accumulation potential, accumulation time, pH, scan rate, electrolyte, and interfering agents were studied to obtain the intensive peak signal of the analyte. The presented method is validated and successfully performed for the determination of the SUL tablet and capsule. The fabricated nanosensor was carried out for the detection of SUL in the urine. Excellent recoveries among 104.37, 103.82, and 101.95% were obtained for tablet and capsule forms and urine analysis.

Electrochemical Behavior and Square-Wave Stripping Voltammetric Determination of Roflumilast in Pharmaceutical Dosage Forms

BACKGROUND

Bronchial asthma and chronic obstructive pulmonary disease (COPD) are among the most common chronic diseases. Roflumilast is a novel, potent, selective, and long-acting phosphodiesterase 4 (PDE-4) inhibitor for the treatment of bronchial asthma and COPD. It has anti-inflammatory effects, and it has been shown to reduce exacerbations and improve pulmonary function in patients with COPD. Although there have been some other analytical methodologies reported for the determination of roflumilast in pharmaceutical dosage forms, there has not yet been any electrochemical methodology proposed for determination of this unique active pharmaceutical ingredient in its dosage forms.

OBJECTIVE

The aim of this study was to develop an easily applied, selective, sensitive, accurate, and precise square-wave stripping voltammetric (SWSV) method for the determination of roflumilast in its pharmaceutical dosage forms. In addition, the electrochemical behavior of roflumilast was investigated.

METHODS

The proposed method was based on electrochemical reduction of roflumilast at a hanging mercury drop electrode (HMDE) in 0.1 M K2HPO4 and 0.1 M Na2B4O7 (1:1, v/v) buffer at pH 5.0. Two reduction peaks were observed at -1150 mV and -1260 mV with 30 s of accumulation time and -850 mV of accumulation potential time versus Ag/AgCl reference electrode.

RESULTS

The highest peak current values with the best peak definition were observed at a frequency of 50 Hz, scan increment of 5 mV, and pulse amplitude 25 mV. The proposed method was validated by evaluating validation parameters such as linearity, sensitivity, repeatability, accuracy, precision, selectivity, recovery, robustness, and ruggedness. A good linear correlation (r=0.9948) was obtained between the electrochemical response of roflumilast and its concentration in the range of 0.74-3.05 μg mL-1 under the optimum conditions. The obtained accuracy results were between 2.04% and -2.04% while the relative standard deviation of the results was at least 2.78% for intraday and inter-day studies. The mean recovery for the real applications was 100.63% ± 0.52. The electrochemical behavior of roflumilast was investigated by cyclic voltammetry. The cyclic voltammogram of roflumilast exhibited two peaks and the reduction reaction was reversible.

CONCLUSION

This developed and validated SWSV method was applied successfully for the determination of roflumilast in tablet dosage form (Daxas®) to assess active roflumilast content. Since high- -performance liquid chromatography is a dominant technique in industry for quality control of active pharmaceutical ingredients, the finding in the present study demonstrated that square-wave stripping voltammetry could be easily utilized in routine applications to determine roflumilast content in its dosage forms.