Eco-friendly estimation of isosorbide dinitrate and hydralazine hydrochloride using Green Analytical Quality by Design-based UPLC Method

Abstract

Isosorbide dinitrate (ISD) and hydralazine hydrochloride (HDZ) are critical drugs for the treatment of heart failure. Currently, no available analytical method for the determination of ISD and HDZ exists as per the literature that combines UPLC and Green Analytical Quality by Design, which is critical for designing a method that is sustainable for long-term use. This study proposes an eco-friendly determination of isosorbide dinitrate (ISD) and hydralazine hydrochloride (HDZ) using a Green Analytical Quality by Design-based UPLC Method. The developed technique is capable of separating ISD and HDZ, as well as their degradation products, using a Phenomenex C18 (50 × 2.1 mm, 2 μm) column containing ethanol and 0.1% trifluoroacetic acid (60 : 40% v/v) at a flow rate of 0.5 mL min^-1. This technique was validated and established a linearity range of 10-60 μg mL^-1 and 18.75-112.5 μg mL^-1, with R ² of 0.9998 and 0.9992 for ISD and HDZ, respectively along with accuracy, reproducibility, and selectivity. The new approach was further evaluated using five different assessment techniques such as National Environmental Methods Index, Analytical Eco-Scale, Green Analytical Procedure Index, Analytical Method Greenness Score, and Analytical GREEnness Metrics, and was determined to be environmentally benign. Based on these results, we have concluded that the developed UPLC technique with the combined approach of Green Analytical Quality by Design for determining stability might benefit in the creation of novel pharmaceutical products such as isosorbide dinitrate and hydralazine.

Fig. 1. Structure of isosorbide dinitrate (a) and hydralazine (b).

Fig. 2. Chromatograms of ISD and HDZ in the Kinetex phenyl hexyl column with ethanol and 0.1% trifluoro acetic acid (60 : 40 v/v) (a), and Phenomenex C18 column with ethanol and 0.1% trifluoro acetic acid (60 : 40 v/v) (b).

Fig. 3. Risk assessment of the proposed method by the Ishikawa fishbone diagram.

Fig. 4. Contour plots for the optimized method: (a) interaction of ethanol and the flow rate; (b) interaction between ethanol and temperature; and (c) interaction between the flow rate and temperature.

Fig. 5. Desirability contour plots for the optimized method: (a) interaction of ethanol and the flow rate; (b) interaction between ethanol and temperature; and (c) interaction between the flow rate and temperature.

Fig. 6. Overlay plots for the optimized method: (a) interaction of ethanol and the flow rate; (b) interaction between ethanol and temperature; and (c) interaction between the flow rate and temperature.

Fig. 7. Peak purity for ISD (a), HDZ (b), and standard graph for ISD and HDZ (c).

Fig. 8. Linearity graphs for ISD (a), HDZ (b), and chromatographic overlay plot for ISD and HDZ in various linear concentrations.

Fig. 9. Forced degradation studies of ISD and HDZ in (a) 0.1 M HCl, (b) 0.1 M NaOH, (c) 3% H₂O₂, (d) photodegradation in UV light, and (e) control without any stress.

Fig. 10. UPLC chromatogram (a) and UV spectrum of ethanol after distillation using HPLC grade ethanol as a blank.

Fig. 11. Green assessment results for the proposed method: (a) NEMI, (b) GAPI, (c) AMGS, and (d) AGREE metrics.