Ionic Liquids in Analytical Chemistry: Applications and Recent Trends

Background:

Ionic liquids (ILs) are a unique class of compounds consisting exclusively of cations and anions that possess distinctive properties such as low volatility, high thermal stability, miscibility with water and organic solvents, electrolytic conductivity and non-flammability. Ionic liquids have been defined as "design solvents", because it is possible to modify their physical and chemical properties by appropriately choosing cations and anions, in order to meet the specific characteristics based on their potential application.

Introduction:

Due of their tunable nature and properties, ILs are considered as the perfect candidates for numerous applications in analytical chemistry including sample preparation, stationary phases in liquid or gas chromatography, additives in capillary electrophoresis, or in mass spectrometry for spectral and electrochemical analysis. In the last years, the number of publications regarding ILs has rapidly increased, highlighting the broad applications of these compounds in various fields of analytical chemistry.

Results:

This review first described the main physico-chemical characteristics of ionic liquids, and subsequently reported the various applications in different subdisciplines of analytical chemistry, including the extraction procedure and separation techniques. Furthermore, in each paragraph the most recent applications of ionic liquids in the food, environmental, biological, etc. fields have been described.

Conclusion:

Overall, the topic discussed highlights the key role of ionic liquids in analytical chemistry, giving hints for their future applications in chemistry but also in biology and medicine.

Fast liquid chromatography-tandem mass spectrometry method for the simultaneous determination of phytocannabinoids in oily based preparations

The reported method aims to be a powerful aid for the simultaneous determination of tetrahydrocannabinol (THC), cannabidiol (CBD), cannabinol (CBN), cannabigerol (CBG), tetrahydrocannabinolic acid (THCA), cannabidiolic acid (CBDA), and tetrahydrocannabivarin (THCV) in oily based preparations. The chromatographic separation was carried out using an Hypersil Gold PFP (50 × 2.1 mm, 1.9 μm) column, using H2O + 2 mM ammonium formate + 0.2 % formic acid (M1) and Methanol + 2 mM ammonium formate + 0.2 % formic acid (M2) as mobile phases. The flow rate was set 0.4 mL/min. Specifically, this method was validated in terms of linearity, limit of detections and quantifications (LODs and LOQs), accuracy (precision and trueness, both intra and interday), selectivity, and matrix effects. This procedure allowed quantifying seven phytocannabinoids in less than 10 min. The validated method shows a good linearity within the range 0.25-1000 ng/mL, while precision and trueness (intra- and inter-day) were below <13.25 % and 7.59 %, respectively. Regarding the matrix effect, the method satisfies all the requirements, except for the THC and THCV, where it reaches about 120 %. This element does not affect the method performances as it has been observed that this value is constant and reproducible and therefore does not involve errors in the quantitative analysis. The method was tested and applied on more 70 different oily based preparations. Furthermore, starting from four different cannabis cultivar (FM2, Bedrolite, Bedrocan, and Bediol), it allowed to evaluate the reproducibility of the magistrali preparations. The real samples, in fact, derive from different local pharmacies, and were analyzed by the accredited UNI CEI EN ISO/IEC 17025:2018, Pharmatoxicology Laboratory (ACCREDIA, lab n. 2274 ASLPE, accreditation number 1822 L), accordingly to the current regulations.

Ethanol Determination in Post-Mortem Samples: Correlation between Blood and Vitreous Humor Concentration

Ethanol (ethylic alcohol) represents the most commonly used drug worldwide and is often involved in clinical and forensic toxicology. Based on several reports, excessive alcohol consumption is the main contributing factor in traffic accidents, drownings, suicides, and other crimes. For these reasons, it becomes essential to analyze the alcohol concentration during autopsy. Although blood is usually used for alcohol analysis in post-mortem cases, it could suffer alterations, putrefaction, and microbial contaminations. As an alternative to whole blood, vitreous humor has been successfully used in medico-legal studies. In this work, post-mortem specimens were analyzed for ethanol determination. The analysis of blood and vitreous humor were carried-out using gas chromatography-flame ionized detector (GC-FID) with a total run time of 6 min. The method was validated in terms of limit of detection, limit of quantification, dynamic range, sensibility, recovery, precision and trueness. A linear regression analysis indicated a coefficient of determination (R²) of 0.9981. The study confirmed no statistically differences between alcohol concentration in blood and vitreous humor, leading vitreous humor as an excellent matrix that could be used as an alternative to whole blood in toxicological analysis in cases where blood is not available.