Sustainable cannabinoids purification through twin-column recycling chromatography and green solvents.

In the present study, twin-column recycling chromatography has been employed for the purification of a Cannabis extract by using a green solvent, ethanol, as the mobile phase. In particular, the complete removal of the psychoactive tetrahydrocannabinol (THC) from a Cannabis extract rich in cannabidiol (CBD) was achieved under continuous conditions. The performance of the method, in terms of compound purity, recovery, productivity and solvent consumption, was compared to that of traditional batch operations showing the potential of the twin-column recycling approach. The employment of a theoretical model to predict the band profiles of the two compounds during the recycling process has facilitated method development, thus further contributing to process sustainability by avoiding trial and error attempts or at least decreasing the number of steps significantly.

RPLC-HILIC and SFC with Mass Spectrometry: Polarity-Extended Organic Molecule Screening in Environmental (Water) Samples.

Trace organic compounds are important in environmental analysis because they impact water quality and introduce potential (eco)toxicological effects. Current analytical methods mostly rely on gas chromatography (GC) or reversed-phase liquid chromatography (RPLC) coupled with (tandem) mass spectrometry. However, neither method can easily separate very polar molecules. This study presents two chromatographic separation strategies, a serial RPLC-hydrophilic interaction liquid chromatography (RPLC-HILIC) coupling and an analytical scale supercritical fluid chromatography (SFC) system, and validates their separation effectiveness as polarity-extended chromatographic methods for 274 environmentally relevant compounds. Compounds tested were grouped into three polarity classes, "very polar" {log D (pH 7) below -2.5}, "polar" {log D (pH 7) -2.5 to +2}, and "non-polar" {log D (pH 7) higher than +2}). Nearly all compounds could be retained in both systems with relative standard deviations of retention times (RT; n = 6) typically between 2 and 5%. Both techniques have considerable benefits when combined with accurate mass spectrometric detection. Molecules RT and accurate mass were recorded in a database for each set up. This information was used for compound screening measurements like "hidden-target screening" in complex environmental matrices (such as wastewater treatment plant effluents). Results of both techniques are complementary and useful for all types of molecules polarity. In this study, more than 80% of the compounds found in wastewater treatment plant effluent samples possessed a negative log D (pH 7) value. This result highlights the basic necessity to include "very polar" compounds in water monitoring techniques and protocols.

Robustness of a method based on the serial coupling of reversed-phase and zwitterionic hydrophilic interaction LC-MS for the analysis of phenols.

We have recently proved that the serial coupling of RP and zwitterionic hydrophilic interaction LC with mass spectrometric detection is a versatile and reliable technique to simultaneously separate polar and apolar compounds in complex samples, for example, phenols in wine. In order to evaluate the system suitability for long-term usage, the robustness of a method based on the serial coupling of RP and zwitterionic hydrophilic interaction LC was evaluated after one year of analyses comprising >1100 injections. The retention time and peak shape of phenol standards and phenols in a red wine were compared to the values previously published. Phenol retention times were shifted <30 s. However, the peak widths were increased, partially due to the deterioration of the stationary phases. Nevertheless, the method was still highly reliable for the analysis of phenols in wine.

Serial coupling of reversed-phase and zwitterionic hydrophilic interaction LC/MS for the analysis of polar and nonpolar phenols in wine.

In the present study, an easy and efficient method based on the serial coupling of analytical reversed-phase and zwitterionic hydrophilic interaction liquid chromatography was developed for the simultaneous separation of polar and nonpolar phenols occurring in wine. The zwitterionic hydrophilic column was connected in series to the reversed-phase one via a T-piece, with which the ACN content in eluent of the second dimension was increased, in order to cope the solvent strength incompatibility between the two columns. The final mobile phase at low-flow rate (≤0.5 mL/min), high-ACN content (90%), and low-salt concentration was directed to an ESI-TOF-MS , for high accurate mass detections. The developed method was applied for the identification of target phenols in several wines. Retention time and peak width intra- and interday repeatability studies proved the reliability of the method for the simultaneous analysis of all the polar and nonpolar analytes in wine. The serial reversed-phase/zwitterionic hydrophilic interaction liquid chromatography coupling offered the possibility to enlarge the number of identified compounds and it represents a valid approach for nontarget analysis of complex samples by a single injection.

Serial coupling of RP and zwitterionic hydrophilic interaction LC-MS: suspects screening of diclofenac transformation products by oxidation with a boron-doped diamond electrode.

The presence of pollutants and their transformation products (TPs) in the water system is a big concern because of possible adverse effects on the aquatic environment. Their identification is still a challenge that requires the combination of different chromatographic techniques. In the current research, serial coupling of RPLC and zwitterionic hydrophilic interaction LC with TOF-MS was investigated as a single separation technique for the screening of suspected TPs from electrochemical oxidation of diclofenac using a boron-doped diamond electrode. Diclofenac oxidation was performed in three water matrices in order to study its transformation in different chemical contexts. 47 TPs resulting from similar oxidation methods were selected from the literature. As in most cases standards were not available, an identification procedure based on accurate mass data and chromatographic behavior was proposed. According to this procedure, 11 suspected TPs, previously analyzed by LC, GC, or ion chromatography, were detected in a single injection. The method was proved to be reliable and versatile and it could be efficiently employed as a comprehensive analytical tool for the simultaneous analysis of compounds in a wide polarity range.

A Direct Real-Time Observation of Anion Intercalation in Graphite Process and Its Fully Reversibility by SAXS/WAXS Techniques.

The process of anion intercalation in graphite and its reversibility plays a crucial role in the next generation energy-storage devices. Herein the reaction mechanism of the aluminum graphite dual ion cell by operando X-ray scattering from small angles to wide angles is investigated. The staging behavior of the graphite intercalation compound (GIC) formation, its phase transitions, and its reversible process are observed for the first time by directly measuring the repeated intercalation distance, along with the microporosity of the cathode graphite. The investigation demonstrates complete reversibility of the electrochemical intercalation process, alongside nano- and micro-structural reorganization of natural graphite induced by intercalation. This work represents a new insight into thermodynamic aspects taking place during intermediate phase transitions in the GIC formation.

Pushing Stoichiometries of Lithium-Rich Layered Oxides Beyond Their Limits.

Lithium-rich layered oxides (LRLOs) are opening unexplored frontiers for high-capacity/high-voltage positive electrodes in Li-ion batteries (LIBs) to meet the challenges of green and safe transportation as well as cheap and sustainable stationary energy storage from renewable sources. LRLOs exploit the extra lithiation provided by the Li1.2TM0.8O2 stoichiometries (TM = a blend of transition metals with a moderate cobalt content) achievable by a layered structure to disclose specific capacities beyond 200-250 mA h g-1 and working potentials in the 3.4-3.8 V range versus Li. Here, we demonstrate an innovative paradigm to extend the LRLO concept. We have balanced the substitution of cobalt in the transition-metal layer of the lattice with aluminum and lithium, pushing the composition of LRLO to unexplored stoichiometries, that is, Li1.2+x (Mn,Ni,Co,Al)0.8-x O2-δ. The fine tuning of the composition of the metal blend results in an optimized layered material, that is, Li1.28Mn0.54Ni0.13Co0.02Al0.03O2-δ, with outstanding electrochemical performance in full LIBs, improved environmental benignity, and reduced manufacturing costs compared to the state-of-the-art.

Uncovering the structure of human red hair pheomelanin: benzothiazolylthiazinodihydroisoquinolines as key building blocks.

Biomimetic oxidation of the pheomelanin precursor 5-S-cysteinyldopa in the presence of Zn(2+) ions led to the isolation of two isomeric products, one of which could be identified as the benzothiazolylthiazinodihydroisoquinoline 5, while the other proved too unstable for a complete characterization. Both these products were converted into more stable oxidized forms, which after ethylchloroformate derivatization were characterized as the ethyl ester/ethoxycarbonyl isoquinolines 8 and 9. Compound 5 exhibited absorption characteristics similar to those of red hair pheomelanin, including a main band around 400 nm in acids. Similarly to red hair pheomelanin and synthetic pigments, 5 afforded on chemical degradation a thiazolylpyridinecarboxylic acid fragment. Model chemical studies allowed the proposal of a formation mechanism for the benzothiazole and dihydroisoquinoline systems in compound 5.

Direct Observation of the Xenon Physisorption Process in Mesopores by Combining In Situ Anomalous Small-Angle X-ray Scattering and X-ray Absorption Spectroscopy.

The morphology and structural changes of confined matter are still far from being understood. This report deals with the development of a novel in situ method based on the combination of anomalous small-angle X-ray scattering (ASAXS) and X-ray absorption near edge structure (XANES) spectroscopy to directly probe the evolution of the xenon adsorbate phase in mesoporous silicon during gas adsorption at 165 K. The interface area and size evolution of the confined xenon phase were determined via ASAXS demonstrating that filling and emptying the pores follow two distinct mechanisms. The mass density of the confined xenon was found to decrease prior to pore emptying. XANES analyses showed that Xe exists in two different states when confined in mesopores. This combination of methods provides a smart new tool for the study of nanoconfined matter for catalysis, gas, and energy storage applications.

Effects of titanium contamination caused by iron-free high-performance liquid chromatography systems on peak shape and retention of drugs with chelating properties.

Iron-free HPLC systems, better known as biocompatible systems, are generally regarded to be chemically more inert compared to conventional HPLC systems. In this work, we studied the chromatographic behavior of some classes of compounds of pharmaceutical interest, analyzed with iron-free systems. Issues typically associated with metal contamination, i.e. strong peak tailing, were observed when using an amide polar-embedded column. Effects of the contamination were visible when anhydrous methanol-acetonitrile was used, indicating that this solvent, albeit generally considered safe for conventional HPLC systems, induce corrosion of iron-free systems. The confirmation of titanium as main acting contaminant came from systematically studying the contribution of each wetted component of the HPLC system on peak shape of affected molecules. Quantification of titanium by ICP-MS analysis of effluents provided further evidence on the source of contamination. A mechanistic description of the complex interaction between titanium ions, organic molecules, and column stationary phase is proposed. In the perspective of developing methods that are fully portable between stainless steel and titanium systems, recommendations are given in terms of potentially sensitive molecules, suitable mobile phase conditions, and type of column to be used.

LC-MS screening techniques for wastewater analysis and analytical data handling strategies: Sartans and their transformation products as an example.

A large number of anthropogenic trace contaminants such as pharmaceuticals, their human metabolites and further transformation products (TPs) enter wastewater treatment plants on a daily basis. A mixture of known, expected, and unknown molecules are discharged into the receiving aquatic environment because only partial elimination occurs for many of these chemicals during physical, biological and chemical treatment processes. In this study, an array of LC-MS methods from three collaborating laboratories was applied to detect and identify anthropogenic trace contaminants and their TPs in different waters. Starting with theoretical predictions of TPs, an efficient workflow using the combination of target, suspected-target and non-target strategies for the identification of these TPs in the environment was developed. These techniques and strategies were applied to study anti-hypertensive drugs from the sartan group (i.e., candesartan, eprosartan, irbesartan, olmesartan, and valsartan). Degradation experiments were performed in lab-scale wastewater treatment plants, and a screening workflow including an inter-laboratory approach was used for the identification of transformation products in the effluent samples. Subsequently, newly identified compounds were successfully analyzed in effluents of real wastewater treatment plants and river waters.

Red human hair pheomelanin is a potent pro-oxidant mediating UV-independent contributory mechanisms of melanomagenesis.

The highest incidence of melanoma in red haired individuals is attributed to the synthesis and phototoxic properties of pheomelanin pigments. Recently, pheomelanin has also been implicated in UV-independent pathways of oxidative stress; however, the underlying mechanisms have remained uncharted. Herein, we disclose the unprecedented property of purified red human hair pheomelanin (RHP) to promote (i) the oxygen-dependent depletion of major cell antioxidants, for example glutathione and NADH; (ii) the autoxidative formation of melanin pigments from their precursors. RHP would thus behave as a unique 'living' polymer and biocatalyst that may grow by simple exposure to monomer building blocks and may trigger autoxidative processes. These results yield new clues as to the origin of the pro-oxidant state in the red hair phenotype, uncover non-enzymatic pathways of melanogenesis, and pave the way to innovative strategies for melanoma prevention.

Main interactions and influences of the chromatographic parameters in HILIC separations.

Hydrophilic interaction liquid chromatography (HILIC) is a popular technique for the separation of polar compounds, which are poorly retained by reversed-phase liquid chromatography. Despite the versatility and the potentiality of this technique, many analysts still feel uncomfortable when approaching it. The HILIC retention mechanism is not completely elucidated and the availability of many different stationary phases may be confusing during method development. Understanding the principles that drive the separation and how they can be influenced by the selection of both stationary phase and chromatographic conditions enhances the range and the quality of possible applications. For this purpose, the review discusses the primary interactions at the basis of HILIC separations and presents an overview of the most common HILIC stationary phases. The effects of the stationary phase type and chromatographic parameters (i.e., organic solvent and salt content, mobile phase pH and column temperature) on each specific interaction are highlighted.

Study of the retention behavior in zwitterionic hydrophilic interaction chromatography of isomeric hydroxy- and aminobenzoic acids.

The retention behavior of fifteen isomeric hydroxy- and aminobenzoic acids in zwitterionic hydrophilic interaction chromatography was studied using a sulfobetaine phase (ZIC-HILIC). By an inspection of their molecular structures, the retention was related to the number, the position and hydrogen bond properties of the functional groups. The effect of the chromatographic conditions was analyzed in order to investigate the retention mechanism of the stationary phase. The increased retention observed for negative charged compounds when the mobile phase pH decreased was ascribed to a diminishing of the electrostatic repulsion with the underivatized silanol groups. Also the salt buffer concentration in the mobile was proved to have a great influence in the modulation of the electrostatic interactions. However, the retention behavior of the benzoic acids was not described by conventional ion-exchange models. Subsequently, a systematical analysis of partition, adsorption, and hydrophilic chromatographic models was presented. The results from the fittings indicated that partition processes govern mainly the ZIC-HILIC separation, but also adsorption processes via hydrogen bonds occurred for hydrogen donor analytes. Finally, the influence of the chromatographic conditions on the water enriched layer in which partition takes place has been evaluated by the elution behavior of toluene.

A melanin-inspired pro-oxidant system for dopa(mine) polymerization: mimicking the natural casing process.

An oxygen-dependent biomimetic system for DOPA, dopamine and norepinephrine polymerization exploiting the redox properties of a 5-S-cysteinylDOPA (CD)-melanin polymer is disclosed. Kinetic, chemical and scanning electron microscopy (SEM) evidence indicates conversion of DOPA into a black insoluble polymer encapsulating the active CD-melanin core.

Pheomelanin-related benzothiazole isomers in the urine of patients with diffuse melanosis of melanoma.

BACKGROUND: Currently used as structural markers for pheomelanin identification and quantitation, benzothiazole compounds derived from isomers of cysteinyldopa have been indicated by recent in vitro studies as new potential pheomelanogenesis intermediates. The presence of benzothiazole compounds in the urine of patients with melanoma with or without diffuse melanosis was investigated. METHODS: Hydrophilic interaction liquid chromatography with zwitterionic stationary phase (ZIC-HILIC) and photo-diode array (PDA) detection was used for analysis of 6-(2-amino-2-carboxyethyl)-4-hydroxybenzothiazole-2-carboxylic acid (BTCA-5), and 7-(2-amino-2-carboxyethyl)-4-hydroxybenzothiazole-2-carboxylic acid (BTCA-2), derived from 5-S-cysteinyldopa (5-S-CD) and 2-S-cysteinyldopa (2-S-CD) isomers, respectively. After minimal sample preparation, isocratic chromatography allowed efficient separation of the compounds, which were safely identified by their typical absorption features. RESULTS: Three patients with diffuse melanosis, 16 patients with melanoma (stages III and IV) and three healthy subjects were investigated. The urinary BTCAs were found to be highly associated with melanosis but more loosely to excreted 5-S-CD. Analysis of the pigmented fraction of urine following alkaline hydrogen peroxide degradation and quantitation of BTCAs provided evidence for the presence of pheomelanins at high levels in patients with melanosis. CONCLUSION: Identification of free BTCA isomers in urine provides a significant contribution in the field of urinary melanogens, and has important implications for biosynthetic activity of normal and pathologic melanocytes.

Isomeric cysteinyldopas provide a (photo)degradable bulk component and a robust structural element in red human hair pheomelanin.

Alkaline H(2)O(2) degradation of red hair pheomelanin gave, besides 6-(2-amino-2-carboxyethyl)-2-carboxy-4-hydroxybenzothiazole (BTCA), a new product which was identified as 7-(2-amino-2-carboxyethyl)-2-carboxy-4-hydroxybenzothiazole (BTCA-2) originating from 2-S-cysteinyldopa (2SCD) derived units. BTCA-2 was also obtained from a variety of pheomelanic tissues and synthetic pigments. Simultaneous determination of BTCA and BTCA-2 in segments of red hair locks taken at variable distances from the scalp in a group of 19 individuals indicated an abrupt drop of BTCA yields on passing from root to tip, whereas BTCA-2 values remained virtually constant throughout hair length. Analysis of 4-amino-3-hydroxyphenylalanine (AHP) and 3-aminotyrosine (AT) in the same lock segments showed a closely similar trend, whereas yields of thiazole-2,4,5-tricarboxylic acid (TTCA) increased with increasing the distance from the scalp. Prolonged exposure of hair locks to sunlight caused a significant decrease in BTCA-, but not BTCA-2-yielding elements. Finally, model studies showed a substantial degradation of 5SCD-, but not 2SCD-derived units, during pheomelanin synthesis in vitro. It is concluded that red hair pheomelanin consists of a degradable 5SCD-derived bulk component associated with stable 2SCD-derived units. Structural degradation occurs during hair growth probably as a result of oxidative processes related in part to sun exposure.