Employment of a natural deep eutectic solvent as a sustainable mobile phase additive for improving the isolation of four crucial cardiovascular drugs by micellar liquid chromatography

Highlights

• High performance of natural deep eutectic solvent in micellar liquid chromatography.

• Designing a green mobile phase composition for cardiovascular drug analysis.

• Excellent separation of cardiovascular drugs with the aid of natural deep eutectic solvent.

• Finding the best experimental conditions by using the experimental design strategy.

• Fast and affordable analysis of four crucial prescribed cardiovascular drugs.

Abstract

Modification of micellar liquid chromatography (MLC) with a natural deep eutectic solvent (NADES) and butanol was effectively performed for analysis of four crucial cardiovascular drugs namely aspirin, atorvastatin, metformin, and metoprolol. The multivariate software tools were employed for screening and optimizing the primary experimental parameters including sodium dodecyl sulphate concentration ([SDS]) as well as the volume percentages of NADES, butanol, and glacial acetic acid (GAC). By using the desirability function, the optimal framework of the mobile phase was obtained at volume ratio of 83:10:3.5:3.5, respectively, for SDS (0.09 mol L⁻¹), butanol, NADES, and GAC. Moreover, the curvature and effect plots were applied for evaluating the robustness of the procedure. At the optimal conditions, the drugs were excellently separated within a total analysis time of 12 min when the flow rate of the mobile phase was 1 mL min⁻¹. To certify the performance of the developed procedure, the Food and Drug Administration guidelines for bioanalytical analysis have been implemented. The designed MLC system was successfully utilized for the quantification of the drugs in urine and plasma samples.

Introduction

Cardiovascular diseases (CVDs) are introduced as a group of diseases that are attributable to the disorders of the heart and blood vessels [1]. These include coronary artery diseases, valvular heart disease, hypertensive disease, heart failure, stroke, cardiomyopathy, heart arrhythmia, etc. As stated by the World Health Organization, CVDs are the primary source of death [1]. However, about 90% of CVDs are preventable through treating the risk factors [2]. Diabetes, blood lipids, and high blood pressure are considered as the extremely important risk factors of CVDs [1]. Therefore, antihypertensive, anti-diabetic and lipid-lowering medications are ordinally prescribed along with cardiovascular drugs for treatment of CVDs [3]. Moreover, anti-diabetic drugs are widely used to minimize cardiovascular risk in patients with type 2 diabetes [4].

Metoprolol (MTP) is a kind of β-blocker that has been extensively used for the treatment of CVDs such as hypertension, heart failure and heart arrhythmia. It can reduce the high blood pressure level and decrease chest pain [5]. Aspirin, also named acetylsalicylic acid (ASA), is an anti-pain, anti-inflammatory and anti-platelet drug. It is effective for primary prevention of CVDs such as heart attacks, ischemic stroke, and unstable angina in people at high cardiovascular risk. Additionally, ASA has been recommended for the prevention of certain kinds of cancer, particularly bowel cancer [6]. Atorvastatin (ATV) is a lipid-lowering prescribed medication that has been extremely popular to regulate the blood pressure of people with hyperlipidemia disorders and CVDs [7]. Metformin (MTF) is an extensively prescribed anti-diabetic drug for reducing cardiovascular complications in patients with type 2 diabetes which is also valuable in the reduction of blood triglyceride and cholesterol. Furthermore, MTF displays worthwhile effects on decreasing cardiovascular risk and it is also advised as an anti-cancer drug [8]. Since these four medications are prescribed in the treatment of CVDs, their simultaneous separation and measurement are strongly demanded.

According to a literature review, reversed-phase high performance liquid chromatography (RP-HPLC) has been extensively considered as a good choice for quantification of MTP, ASA, ATV, and MTF, individually or simultaneously, along with other medications [[9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19]]. However, a few HPLC methods have been reported for the simultaneous measurement of each two of these drugs. The reported HPLC strategies involved traditional HPLC and micellar liquid chromatography (MLC). In the traditional HPLC tactic, organic solvents are widely employed as the mobile phase. Whereas, in the MLC technique, the aqueous solution of an eco-friendly surfactant is applied instead of unsafe and expensive organic solvents as the mobile phase [20]. Capability in simultaneous isolation of solutes with different polarities and charges, having high robustness and reproducibility, being affordable, and enhancing luminescence detection, are some of the other benefits of the MLC methodology [20]. However, possessing low peak efficiency is its drawback [21]. Applying a small amount of an organic solvent, e.g. butanol, as a modifier in the mobile phase can compensate this weakness [21]. Natural deep eutectic solvents (NADESs) have also been introduced as a unique green efficient modifier in the MLC systems [22,23].

Deep eutectic solvents (DESs) are a combination of two or three environmentally-friendly and biocompatible components with the potential to form intense intermolecular hydrogen bonds. This category of solvents has all the beneficial top features of conventional ionic liquids (ILs) such as non-flammability, non-volatility, excellent solubilization capacity, high chemical stability and recycling possibility. Nevertheless, DESs have some advantages over ILs including owning more convenient synthesis protocols without requiring refining step with hazardous organic solvents, being more cost-effective, possessing much lower toxicity levels, and having more biocompatibility. These great features have led to the widespread employment of DESs as green replacements to both organic solvents and ILs in various fields, especially in separation science [24].

The objective of this research was to develop an MLC mobile phase for rapid separation and analysis of MTP, ASA, ATV, and MTF in biological samples. The modification of the MLC system was performed through using choline chloride (ChCl)-ethylene glycol (EG)-based NADES and butanol. Up to now, this NADES has shown great efficiency in the modification of both traditional RP-HPLC and MLC systems for analysis of polar and non-polar species [22,23,25]. It should be remarked that to the best of our knowledge, there is not any report in literature for simultaneous determination of the aforementioned drugs.