Ionic liquids as superior solvents for headspace gas chromatography of residual solvents with very low vapor pressure, relevant for pharmaceutical final dosage forms

Thermodynamic characterization of interactions between environmental contaminants and room temperature ionic liquids using static headspace gas chromatography with vacuum ultraviolet detection

Understanding the thermodynamic interactions between an analyte and the sample phase is of paramount importance when choosing a co-solvent in headspace analysis. A sample phase - gas phase equilibrium partition coefficient (Kp) is used fundamentally to describe the distribution of the analyte between the two phases. Kp determinations by headspace gas chromatography (HS-GC) were acquired by two methods: vapor phase calibration (VPC) and phase ratio variation (PRV). Here, we demonstrated a pressurized - loop headspace system in conjunction with gas chromatography vacuum ultraviolet detection (HS-GC-VUV) to directly calculate the concentration of analytes in the gas phase from room temperature ionic liquids (RTILs) sample phases, using pseudo-absolute quantification (PAQ). PAQ, an attribute of VUV detection, allowed for quick determination of Kp and other thermodynamic properties, such as enthalpy (ΔH) and entropy (ΔS) of the system through the use of van't Hoff plots in the temperature range of 70-110 °C. The Kp determinations by PAQ were comparable to those obtained using the VPC method with percent difference ranging from ≤ 1-33%. Kp determinations were made for analytes (cyclohexane, benzene, octane, toluene, chlorobenzene, ethylbenzene, m-,p-, and o-xylene) at the varying temperatures (70-110 °C) using different RTILs (1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][ESO₄]), 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][DEP]), and tris(2-hydroxyethyl)methylammonium methylsulfate ([MTEOA][MeOSO₃])) and (1-ethyl-3-methylimidazolium bis(trisfluoromethanesulfonyl)imide ([EMIM] [NTF₂])). The results from the van't Hoff analysis revealed that [EMIM] cation-based RTILs exhibit strong solute-solvent interactions with analytes that have π- electrons.

Occurrence, detection and ecotoxicity studies of selected pharmaceuticals in aqueous ecosystems- a systematic appraisal

Pharmaceutical compounds (PCs) have globally emerged as a significant group of environmental contaminants due to the constant detection of their residues in the environment. The main scope of this review is to fill the void of information on the knowledge on the African occurrence of selected PCs in environmental matrices in comparison with those outside Africa and their respective toxic actions on both aquatic and non-aquatic biota through ecotoxicity bioassays. To achieve this objective, the study focused on commonly used and detected pharmaceutical drugs (residues). Based on the conducted literature survey, Africa has the highest levels of ciprofloxacin, sulfamethoxazole, lamivudine, acetaminophen, and diclofenac while Europe has the lowest of all these PC residues in her physical environments. For ecotoxicity bioassays, the few data available are mostly on individual groups of pharmaceuticals whereas there is sparsely available data on their combined forms.

Simultaneous Determination of Nine Residual Solvents in Sorafenib Tosylate by Gas Chromatography

BACKGROUND

Direct injection gas chromatography is convenient and quick. The residual solvent with a higher boiling point can be measured by using direct inhection gas chromatography. This method could be developed for residual solvents analysis of sorafenible tosylate.

OBJECTIVE

In the present investigation, the injection method was developed and validated for the detection and quantification of residual solvents in sorafenib tosylate.

METHOD

The nine kinds of residual solvents were separated using direct injection gas chromatographic technology, and a quantitative analysis was performed. Analytical performance of the proposed injection method was validated as per the defined guidelines with respect to linearity, accuracy, precision, robustness, and specificity.

RESULTS

Under the optimized conditions, simultaneous separation and determination of nine kinds of residual solvents, including methanol, acetonitrile, ethyl acetate, tetrahydrofuran, chlorobenzene, toluene, acetone, dichloromethane, and N, N-dimethylformamide were carried out using a DB-WAXETR polyethylene glycol Inertap Pure-WAX column (30 m × 0. 32 mm × 0.25 µm) for separation. The calibration plot was found to be linear, accurate, precise, robust, and specific for direct injection gas chromatography. The residual solvents in sorafenib tosylate were quantified by the developed method.

CONCLUSIONS

The present method was successfully applied for analysis of residual solvents in sorafenib tosylate. Similarly, the method can be used for quality control and stability testing of other medicines.

HIGHLIGHTS

A validated GC assay for the combined analysis of the nine solutions which offered a reference method for the detection of residual solvents in other medicines.

Application of On-Line Sorbentless Cryogenic Needle Trap Extraction Coupled with GC-FID for Analysis of Some Organic Volatile Impurities in Solid Pharmaceuticals

An automated sorbentless cryogenic needle trap device (ASCNTD) was developed for the extraction of organic volatile impurities (OVIs) from solid pharmaceuticals prior to their determination by gas chromatography (GC). In this method, a new set up was designed and used to extraction of several OVIs from ceftazidime, ceftriaxone sodium and amoxicillin. For this purpose, a proper amount of the sample was transferred into the extraction vessel. The sample headspace components were started to circulate through a needle with a flow rate of 20 mL min-1. The OVIs were trapped on the inner surface of a needle placed on top of the sample by flowing liquid nitrogen. After a predetermined time, the coiled nichrome resistance wire placed into the hollow ceramic rod was heated and the trapped analytes were desorbed and swept into the GC capillary column using the carrier gas. The effective parameters such as volume of the sample vial, headspace flow rate, extraction temperature and time, and desorption conditions have been investigated. Qualification studies reveal that pyridine (as a degradation product of ceftazidime), methylene chloride, diethylamine, triethylamine, isopropyl alcohol and n-butyl acetate are the main impurities in the studied pharmaceuticals. Detected OVIs were quantitated using external standard method. The obtained relative standard deviation values were <8%, and the limits of detection (LOD) for the detected OVIs were in the range of 1-34 ng g-1.

Determination of physicochemical properties of ionic liquids by gas chromatography

Over the years room temperature ionic liquids have gained attention as solvents with favorable environmental and technical features. Both chromatographic and conventional methods afford suitable tools for the study of their physicochemical properties. Use of gas chromatography compared to conventional methods for the measurement of physicochemical properties of ionic liquids have several advantages; very low sample concentrations, high accuracy, faster measurements, use of wider temperature range and the possibility to determine physicochemical properties of impure samples. Also, general purpose gas chromatography instruments are widely available in most laboratories thus alleviating the need to purchase more specific instruments for less common physiochemical measurements. Some of the main types of physicochemical properties of ionic liquids accessible using gas chromatography include gas-liquid partition constants, infinite dilution activity coefficients, partial molar quantities, solubility parameters, system constants of the solvation parameter model, thermal stability, transport properties, and catalytic and other surface properties.

The Influence of Ionic Liquids on the Effectiveness of Analytical Methods Used in the Monitoring of Human and Veterinary Pharmaceuticals in Biological and Environmental Samples-Trends and Perspectives

Recent years have seen the increased utilization of ionic liquids (ILs) in the development and optimization of analytical methods. Their unique and eco-friendly properties and the ability to modify their structure allows them to be useful both at the sample preparation stage and at the separation stage of the analytes. The use of ILs for the analysis of pharmaceuticals seems particularly interesting because of their systematic delivery to the environment. Nowadays, they are commonly detected in many countries at very low concentration levels. However, due to their specific physiological activity, pharmaceuticals are responsible for bioaccumulation and toxic effects in aquatic and terrestrial ecosystems as well as possibly upsetting the body's equilibrium, leading to the dangerous phenomenon of drug resistance. This review will provide a comprehensive summary of the use of ILs in various sample preparation procedures and separation methods for the determination of pharmaceuticals in environmental and biological matrices based on liquid-based chromatography (LC, SFC, TLC), gas chromatography (GC) and electromigration techniques (e.g., capillary electrophoresis (CE)). Moreover, the advantages and disadvantages of ILs, which can appear during extraction and separation, will be presented and attention will be given to the criteria to be followed during the selection of ILs for specific applications.