Greening pharmaceutical applications of liquid chromatography through using propylene carbonate–ethanol mixtures instead of acetonitrile as organic modifier in the mobile phases

Greener and Whiter Analytical Chemistry Using Cyrene as a More Sustainable and Eco-Friendlier Mobile Phase Constituent in Chromatography

Cyrene (dihydrolevoglucosenone) was evaluated for the first time as a potential sustainable mobile phase solvent in reversed-phase chromatography. As a benign biodegradable solvent, Cyrene is an attractive replacement to classical non-green organic chromatographic solvents such as acetonitrile and a modifier, co-eluent to known green solvents such as ethanol. Compared to ethanol, Cyrene is less toxic, non-flammable, biobased, biodegradable, and a cheaper solvent. A fire safety spider chart was generated to compare the properties of Cyrene to ethanol and show its superiority as a greener solvent. Cyrene's behavior, advantages, and drawbacks in reversed-phase chromatography, including the cut-off value of 350 nm, elution power, selectivity, and effect on the column, were investigated using a model drug mixture of moxifloxacin and metronidazole. A monolithic C18 (100 × 4.6 mm) column was used as a stationary phase. Different ratios of Cyrene: ethanol with an aqueous portion of sodium acetate buffer mobile phases were tested. A mobile phase consisting of Cyrene: ethanol: 0.1 M sodium acetate buffer pH 4.25 (8:13:79, v/v/v) was selected as the most suitable mobile phase system for separating and simultaneously determining metronidazole and moxifloxacin. The greenness and whiteness of the method were evaluated using the qualitative green assessment tool AGREE and the white analytical chemistry assessment tool RGB12. Further potentials of Cyrene as a solvent or modifier in normal phase chromatography, liquid chromatography-mass spectrometry, and supercritical fluid chromatography are discussed.

Reaction of the Phytochemistry Community to Green Chemistry: Insights Obtained Since 1990

This review article aims to study how phytochemists have reacted to green chemistry insights since 1990, the year when the U.S. Environmental Protection Agency launched the "Pollution Prevention Act". For each year in the period 1990 to 2019, three highly cited phytochemistry papers that provided enough information about the experimental procedures utilized were sampled. The "greenness" of these procedures was assessed, particularly for the use of solvents. The highly hazardous diethyl ether, benzene, and carbon tetrachloride did not appear in the papers sampled after 2010. Advances in terms of sustainability were observed mainly in the extraction stage. Similar progress was not observed in purification procedures, where chloroform, dichloromethane, and hexane regularly have been employed. Since replacing such solvents in purification procedures should be a major goal, potential alternative approaches are discussed. Moreover, some current initiatives toward a more sustainable phytochemical research considering aspects other than only solvents are highlighted. Although some advances have been achieved, it is believed that natural products chemists can play a major role in developing a novel ecological paradigm in chemistry. To contribute to this objective, six principles for performing natural products chemistry consistent with the guidelines of green chemistry are proposed.

Combining environmental, health, and safety features with a conductor like Screening Model for selecting green solvents for antibiotic analyses

Extraction and chromatographic techniques for analyzing pharmaceutically active compounds necessitate large quantities of organic solvents, resulting in a high volume of hazardous waste. The concept of green solvents focuses on protecting the environment by reducing or even eliminating the use of toxic solvents. The main objective of this critical review article is to build a framework for choosing green solvents for antibiotic analyses. The article briefly discusses the chemical properties of ciprofloxacin, sulfamethoxazole, tetracycline, and trimethoprim, and the current state of methodologies for their analyses in water and wastewater. It evaluates the greenness of solvents used for antibiotic analyses and includes insights on the comparison between conventional and green solvents for the analyses. An economic and environmental health and safety analysis combined with a Conductor-like Screening Model for Real Solvent (COSMO-RS) molecular simulation technique for predicting extraction efficiency was used in the evaluation. Methyl acetate and propylene carbonate tied for the greenest solvents from an environmental and economic perspective, whereas the COSMO-RS approach suggests dimethyl sulfoxide (DMSO) as the most suitable candidate. Although DMSO ranked third environmentally and economically, after methyl acetate and propylene carbonate, it would be an ideal replacement of hazardous solvents if it could be manufactured at a lower cost. DMSO showed the highest extraction capacity, as it can interact with antibiotics through hydrophobic interaction and hydrogen bonding. This article can be used as a green solvent selection guide for developing sustainable processes for antibiotic analyses.

Green comprehensive two-dimensional liquid chromatography (LC × LC) for the analysis of phenolic compounds in grape juices and wine

Grape juices and wines are rich in numerous groups of polyphenolic compounds which require a dedicated separation technique for such complex samples. LC × LC is considered the best technique for the analysis of such samples as it can achieve better resolution and higher peak capacity compared to 1D LC. The ever-growing demand for protecting the environment necessitates reducing or eliminating hazardous solvents to improve the environmental friendliness of analytical procedures. In this study, propylene carbonate was used as an eco-friendly mobile phase component in comprehensive two-dimensional liquid chromatography to analyze phenolic compounds in grape juices and a dealcoholized wine sample. Novel green RPLC × RPLC-DAD and RPLC × RPLC-MS methods were developed for the first time to identify phenolic compounds in five samples (two red grape juice samples, two white grape juice samples, and one dealcoholized wine sample). Four different RPLC × RPLC systems were developed; three systems were connected to a diode array detector (RPLC × RPLC-DAD), while the fourth system was connected to DAD and MS detectors (RPLC × RPLC-DAD-ESI-MS). Solvent X (propylene carbonate:ethanol, 60:40) was adopted as a green organic modifier in the first dimension (¹D) and methanol in the second dimension (²D). The practical peak capacity and the surface coverage were calculated as metrics to measure the separation performance of all proposed systems. The orthogonality values for the setups ranged from 0.64 to 0.92 when calculated by the convex hull method, and from 0.54 to 0.80 when calculated by the asterisk equations method. The practical peak capacity production rate ranged from 14.58 to 22.52 peaks/min. The results revealed that the phenolic compounds were separated efficiently with good coverage of the 2D separation space and high peak capacity. A total of 70 phenolic compounds were detected based on MS data and information from the literature.

Assessment of greenness for the determination of voriconazole in reported analytical methods

Analytical research with adverse environmental impact has caused a severe rise in concern about the ecological consequences of its strategies, most notably the use and emission of harmful solvents/reagents into the atmosphere. Nowadays, industries are searching for the best reproducible methods. Voriconazole is a second-generation azole derivative used effectively in the treatment of Candida and Aspergillus species infections and oropharyngeal candidiasis in AIDS patients. Recently it has become the drug of choice in treating mucormycosis in several countries, which raises the need for production in large quantities. The present review deals with various recent important analytical techniques used to estimate voriconazole and its combination in pharmaceutical formulations and biological fluids. The methods show their own unique way of analyzing voriconazole in different matrices with excellent linearity, detection, and quantification limits. Additionally, this article deals with methods and solvents analyzed for their impact on the environment. This is followed by estimating the degree of greenness of the methods using various available assessment tools like analytical eco-scale, national environmental method index, green analytical procedure index, and AGREE metrics to confirm the environmental impact. The scores obtained with the evaluation tools depict the quantum of greenness for the reported methods and provide an ideal approach adopted for VOR estimation. Very few methods are eco-friendly, which shows that there is a need for the budding analyst to develop methods based on green analytical principles to protect the environment.

Development of a Simple High-Performance Liquid Chromatography-Based Method to Quantify Synergistic Compounds and Their Composition in Dried Leaf Extracts of Piper Sarmentosum Roxb

There is a growing demand to enhance pharmaceutical and food safety using synergistic compounds from Piper sarmentosum Roxb., such as polyphenols and water-soluble vitamins. However, information on standardized analytical methods to identify and quantify these compounds of interest is limited. A reversed-phase high-performance liquid chromatography with diode-array detection (HPLC-DAD)-based method was developed to simultaneously detect and quantify the amounts of tannin, flavonoid, cinnamic acid, essential oil, and vitamins extracted from P. sarmentosum leaves using methanol, chloroform, and hexane. Commercially and non-commercially-cultivated P. sarmentosum leaves were subjected to seven different drying treatments (shade; sun; air oven at 40 °C, 60 °C, 80 °C, and 100 °C; and freeze-drying) for three consecutive months. Most compounds were detected most efficiently at a detection wavelength of 272 nm. The developed method displayed good detection limits (LOD, 0.026–0.789 µg/mL; LOQ, 0.078–2.392 µg/mL), linearity (R2 > 0.999), precision (%RSD, <1.00), and excellent accuracy (96–102%). All P. sarmentosum leaf extracts were simultaneously tested and analytically compared without time-consuming fractionation. Methanolic plant extracts showed better peak area and retention time splits compared to chloroformic and hexanoic extracts. Differences in synergistic compound composition were dependent on the type of drying treatment but not on cultivation site and time of sampling. Flavonoid was identified as the dominant phytochemical component in P. sarmentosum leaves, followed by the essential oil, cinnamic acid, ascorbic acid, and tannin. Overall, we present a simple and reproducible chromatographic method that can be applied to identify different plant compounds.

Greening Reversed-Phase Liquid Chromatography Methods Using Alternative Solvents for Pharmaceutical Analysis

The greening of analytical methods has gained increasing interest in the field of pharmaceutical analysis to reduce environmental impacts and improve the health safety of analysts. Reversed-phase high-performance liquid chromatography (RP-HPLC) is the most widely used analytical technique involved in pharmaceutical drug development and manufacturing, such as the quality control of bulk drugs and pharmaceutical formulations, as well as the analysis of drugs in biological samples. However, RP-HPLC methods commonly use large amounts of organic solvents and generate high quantities of waste to be disposed, leading to some issues in terms of ecological impact and operator safety. In this context, greening HPLC methods is becoming highly desirable. One strategy to reduce the impact of hazardous solvents is to replace classically used organic solvents (i.e., acetonitrile and methanol) with greener ones. So far, ethanol has been the most often used alternative organic solvent. Others strategies have followed, such as the use of totally aqueous mobile phases, micellar liquid chromatography, and ionic liquids. These approaches have been well developed, as they do not require equipment investments and are rather economical. This review describes and critically discusses the recent advances in greening RP-HPLC methods dedicated to pharmaceutical analysis based on the use of alternative solvents.

New approach for determination of the degradation products of fenspiride hydrochloride found in oral liquid formulations

Fenspiride hydrochloride (FNS) is used in treating chronic inflammatory diseases, most commonly as a liquid oral solution. FNS produces degradation products along with fenspiride N-oxide (FNO) and 1-phenylethyl-4-hydroxy-4-aminomethyl piperidine hydrochloride (PHAP). We aimed to develop and validate a chromatographic method in order to identify the main degradation products in the presence of other compounds from a liquid preparation. The method used a dual gradient using two buffer solutions: the first with pH 4.5 (buffer 1, pH 4.5-MeOH 90:10%, v/v) and the second with pH 2.9 (buffer 2, pH 2.9-acetronitrile-methanol, 65:15:10%, v/v/v). As mentioned, there was a modification of the organic mixture, starting with 10% methanol and ending with a mixture of acetonitrile-methanol (15:10%, v/v). The flow-rate was 1.5 mL/min. According to the elution program, experimental conditions started with 100% solution S1, which decreased to 0% and, simultaneously, solution S2 increased to 100% during the first 10 min and was maintained for a further 5 min. After 15 min, initial conditions were re-established. The linearity interval was 0.5-2 μg/mL and the minimum correlation coefficient was 0.999. The recovery factor was 100.47-103.17% and the limit of quantification was 0.19-0.332 μg/mL. Intra-day maximum precision was 4.08% for FNS and 2.65% for PHAP. This double-gradient mobile phase produced good specificity in relation to the degradation products of FNS and other constituents of the oral liquid formulation. Forced degradation studies revealed other related substances that were confirmed in mass balance analyses. Degradation products were confirmed in acidic, basic and oxidative media.

Ethyl lactate as a greener alternative to acetonitrile in RPLC: a realistic appraisal

Appropriate substitution of acetonitrile (ACN) in mobile phases for reversed-phase liquid chromatography (RPLC) by low toxicity, ecologically friendly alternative solvents emerges as a greener approach in separation sciences. Ethyl lactate is considered as a green solvent in organic synthesis, industrial extraction processes and many other applicative fields. Its ability to substitute ACN in mobile phases for RPLC applications was barely investigated. The feasibility of such a replacement was tested for the separation of the mixture of 16 polycyclic aromatic hydrocarbons listed by the Environmental Protection Agency. The analytical approach was found to be achievable, with some compromises in terms of elution order, peak efficiency and UV detectability. Thermodynamic aspects of the chromatographic process were also comparatively assessed. Correlations between the elution order and some molecular descriptors were also discussed.

Application and validation of an eco-friendly TLC-densitometric method for simultaneous determination of co-formulated antihypertensive agents

Application and validation of eco-friendly TLC-densitometric method for simultaneous determination of co-formulated antihypertensive agents.

Alternative sample diluents in bioanalytical LC–MS

The problem of sample diluent in bioanalytical LC–MS is reviewed with a special focus on large-volume injections and non-miscible solvents with mobile phase components. These issues are related to the sample preparation approach, which in many instances provides the sample diluent before injecting this into the chromatographic column. The sample volume influences the quantitation limit of the chromatographic method, while its nature may influence the retention process of the injected analytes. The literature reports a few papers that are focused on alternative sample diluents in bioanalytical LC–MS that are generally non-miscible with mobile phase. The principle of this approach and some of its current bioanalytical applications from literature are discussed. However, more applications and more publications from HPLC users and vendors are expected in this field, which could prove its analytical importance and potential in bioanalysis.