Journal of chromatography open最新文献

Lactofen is a chiral restricted-use herbicide, classified as toxicity class I by the Environmental Protection Agency (EPA), commonly used to control broadleaved weeds. While the observed herbicidal activity mostly derives from the (S)-(+)-enantiomer, formulations have been manufactured as a mixture of both enantiomers. In this work, we present a quantitative method for the enantiomeric determination of lactofen in commercial formulations based on the development of a second-order calibration to assist the selectivity of chiral separation under reversed-phase liquid chromatographic mode coupled to diode array detection. Chromatographic conditions were aimed to minimize analysis time and solvent consumption. This approach is feasible because second-order calibration allows for the quantification of overlapping bands and analytes in the presence of interferences. Chromatographic-spectral matrices were processed by unfolded partial least-squares coupled to residual bilinearization. The proposed methodology was evaluated through validation samples, achieving relative errors of predictions of 2–4 %. Finally, commercial formulations were subjected to minimal sample treatment and analyzed, and figures of merit for real samples were determined. The described methodology results suitable for the determination of enantiomeric purity and quality control in commercial lactofen formulations.

The design of the mobile phase additive useful in HPLC analysis on two types of chiral stationary phases, one based on chiral crown ether, and another based on polysaccharide derivative, was developed. CROWNPAK® CR-I, the chiral stationary phase bearing (R)- or (S)-(3,30-diphenyl-1,10-binaphtyl)-20-crown-6 (1) moiety is a useful CSP to separate primary amine enantiomers. While perchloric acid had been recommended as the mobile phase additive to attain a better separation, we have reexamined the effect of mobile phase additives and revealed that the retention of an ammonium ion is enhanced by a chaotropic or a hydrophobic anion in a water-based mobile phase like well-known ion pair chromatography in an RPLC. However, the retention was enhanced in reverse by a rather cosmotropic or a hydrophilic anion in an acetonitrile (ACN)-based mobile phase. These results looking contradictory to each other may be rationalized both in the basis of ion pair chromatography. A similar but smaller effect of pairing anion species was also observed on a polysaccharide-based CSP. Based on these findings, some types of mobile phase have been proposed and some of them were demonstrated to be compatible with liquid chromatography-electrospray ionization-mass spectrometry (ESI LC/MS).

The chirality of amino acids in extraterrestrial materials may provide an insight into the origin of the essential l-enantiopure amino acids in the terrestrial biosphere. In 2020, the Hayabusa2 mission succeeded in bringing back surface materials from the C-type asteroid (162173) Ryugu to the Earth. Amino acids were one of the targeted organic molecules to be studied in the Ryugu samples. To analyze the various structural isomers of amino acids, which were expected to be present, from the limited amount of the returned samples, the development of a highly-sensitive and selective analytical method was necessary. In the present study, a three-dimensional high-performance liquid chromatography (3D-HPLC) system has been developed for the enantioselective determination of five proteinogenic and three non-proteinogenic amino acids in the Ryugu samples, in which amino acids in the sample were separated by reversed-phase, anion-exchange and enantioselective columns after the fluorescence derivatization with 4-fluoro-7-nitro-2,1,3-benzoxadiozole. The applicability of the analytical system to the extraterrestrial samples was evaluated by analyzing several types of carbonaceous meteorites before applying the system to the Ryugu samples. In the analysis of the Ryugu samples, all of the target amino acids were successfully determined quantitatively. Non-proteinogenic amino acids including 2-amino-n-butyric acid, isovaline and norvaline, rarely present in the terrestrial environment, were found as almost racemic mixtures with 47.1 to 55.2%l.

In our previous paper, we introduced a new method for the enantioseparation of cathinones on chiral zwitterion ion exchangers by SFC-ESI-MS with an inverse make-up solvent gradient. The inverse gradient enabled us to stabilize electrospray ionization while simultaneously increasing MS response. In this study, we fine-tuned our previously optimized SFC-ESI-MS method and compared its efficiency with that of the default ESI-MS method. To enhance analyte detection, we designed a complex series of experiments in which all combinations of the following three parameters were evaluated: cone voltage (5 to 27 V), probe temperature (250 to 550 °C) and capillary voltage for positive ionization (0.3 to 1.5 kV). After optimization, various ratios of the make-up solvent (methanol/water/formic acid) introduced before entering the ESI ion source were also tested. Despite this comprehensive testing regime, there were no significant differences between the results obtained for the tuned and default ESI-MS parameters. Similarly, the most suitable make-up solvent composition was the originally used ratio of 90/10/0.1 (v/v/v). These results reinforce the findings of our previous paper, in which we optimized the make-up solvent flow rate and showed its significant impact on ESI-MS response.

Reverse-phase liquid chromatography has been a widely used analytical technique in many laboratories around the world for several decades. In reverse-phase liquid chromatography method development applications, for the majority of analytical chemists, the use of organic phase modifiers is limited to acetonitrile and methanol. In an effort to minimise the impact on the environment while improving analyst health and safety, analytical method development has seen a rise in interest in greening analytical procedures, including the use of environmentally friendly alternative organic phase modifiers. Another focus of exploring alternative organic modifiers is to maximise the selectivity space of the typically used octadecylsiloxane-bonded silica stationary phase. The aim of this review is to explore how analytical chemists employed alternative solvents as organic phase modifiers in reverse-phase liquid chromatography for various applications and their retention properties.

Tannins, which can be extracted from certain tree barks, are polyphenolic compounds, that gain a lot of interest in industry, as they can be utilized to replace petroleum-based chemicals. Currently, they are used in the leather industry, as flocculants or as adhesives. To further increase their potential, an increase in purity is necessary. To do so, various methods are available, in this study we present a 2-step approach consisting of (i) depolymerization and cleavage of glycosidic bonds and (ii) separation of phenolic-rich and phenolic-poor fractions. Commercially available mimosa tannin is treated with various concentrations of hydrochloric and sulfuric acid (0.4 M and 0.8 M) and separated with chromatographic resin. Resulting fractions are characterized by UV/Vis spectroscopy for phenolic content and antioxidant activity, infrared spectroscopy, NMR, HPLC-DAD and GPC to determine their composition and molecular size as well as their reactivity towards formaldehyde. It was observed that mild acidic cleavage with 0.4 M HCl results in more phenol-rich material (TPC 1124 µgGAE mg⁻¹) while 0.8 M sulfuric acid leads to tannin fractions with higher antioxidative properties. Amberlite resin yields fractions with higher reactivity towards formaldehyde (gel time below 60 s compared to over 90 originally) while the Sephadex fractions present the highest values for total phenolic content.

Propylene oxide (PO) is an important chemical commodity and a chiral building block to prepare pharmaceutical compounds. It is crucial to develop a sensitive and robust chiral method that can be used to assess the enantiomeric purity of PO and safeguard the quality and safety of pharmaceutical products in commercial quality control (QC) laboratories. A chiral gas chromatography (GC) method based on direct enantioseparation of PO enantiomers on a 50-meter Chiraldex™ A-TA open capillary column was successfully developed for determination of enantiomeric impurity (S)-PO in (R)-PO. However, it was revealed that the chiral GC method lacked adequate robustness for routine use. Consequently, a chiral high-performance liquid chromatography (HPLC) method was developed through pre-column derivatization of PO with 2-naphthalenethiol followed by enantioseparation on a Lux Cellulose-1 (250 mm × 4.6 mm, 5 µm) column. The chiral HPLC method has been demonstrated excellent specificity, sensitivity, accuracy and robustness through method validation and robustness evaluation, thus establishing its suitability for routine use in QC laboratories.

Acephate and malathion are prevalent chiral organophosphate insecticides, giving rise to more toxic chiral metabolites such as methamidophos and malaoxon, respectively. Enantioselective separation of chiral pesticides is crucial due to the differing pharmacological, environmental, and toxicological profiles of enantiomers. This study systematically evaluates an enantio‑ and chemoselective performance of eight polysaccharide-based chiral columns (Chiralcel OB-H, Chiralcel OD-H, Chiralcel OJ-R, Chiralpak AD-H, Chiralpak AS-H, Chiralpak IG-3, Chiralpak IK-3, and Lux-Amylose-2) and ten mobile phases across multimodal elution (normal-phase, polar organic, and reversed-phase conditions). Within the 80 combinations per analyte, the chiral screening highlights specific enantioselectivity trends concerning hydrophilic and hydrophobic compounds when utilizing amylose- or cellulose-based polymers under different conditions. Notably, a set of columns including IK-3, OJ-R, AS-H, and AD-H demonstrated superior coverage, achieving at least a 62 % success rate for enantioseparation. For the resolution between the pairs acephate/methamidophos and malathion/malaoxon, where no further optimizations were undertaken, the success rate for enantio‑ and chemoselectivity was 10 % and 30 %, respectively.

The enantioselective potential of amylose tris (3‑chloro-5-methylphenylcarbamate) based chiral stationary phase in sub/supercritical fluid chromatography and normal phase liquid chromatography was evaluated. To test its enantioselective potential the enantiomeric resolution of a set of nineteen important chiral biologically active compounds was explored. The influence of the cosolvent and different mobile phase additives on the retention, enantioselectivity, and enantioresolution was investigated. The type, as well as the amount of cosolvent used in the mobile phase, are critical for enantioseparation efficiency in both techniques. Using basic or mixed additives in the mobile phases significantly improved enantioseparation and peak shape of different compounds, especially β-blockers. Results showed the high enantioselective potential of the chlorinated amylose-based chiral stationary phase in both chromatographic techniques with overall higher enantiorecognition ability in sub/supercritical fluid chromatography.

Various substances classified as prohibited in sport by the World Anti-Doping Agency (WADA) comprise one or more chiral centers. One such substance is enobosarm ((2S)-3-(4-cyanophenoxy)-N-[4-cyano-3-(trifluoromethyl)phenyl]-2‑hydroxy-2-methylpropanamide, S-ostarine, S-22, MK-2866, GTx-024, VERU-024). Although ostarine is not an approved drug, it has been readily available via Internet-based suppliers, and to date it is unknown to what extent R-ostarine, S-ostarine, or a mixture of both is used in these products. Likewise, such information is not available with regards to urine samples that returned an adverse analytical finding in the context of sports drug testing programs and, hence, this pilot-study aimed at establishing a test method to provide first insights into the presence of R- and S-ostarine in commercially available products and in authentic doping control urine samples.

Here, a chiral liquid chromatographic - mass spectrometric method, employing a teicoplanin-containing (chiral) stationary phase that allows the differentiation of R- and S-enantiomers of ostarine, is presented. Ostarine products were extracted and diluted prior to analysis, while urine samples were prepared for analysis by enzymatic hydrolysis followed by liquid-liquid extraction.

Seven products declaring to contain ostarine were investigated, five of which were ordered via the Internet and two were confiscated and made available by a customs authority. Only 2 of the 5 purchased products contained ostarine. In these two products and the confiscated products, only the ostarine S-enantiomer was found. Further, five authentic doping control urine samples containing the target analyte were subjected to chiral analysis, also confirming the sole presence of the S-ostarine enantiomer.

The developed approach proved suitable for the separation of ostarine enantiomers, which adds further information e.g. in the context of illicit drug production, trafficking, and doping controls, especially when additional details are desirable that might assist in determining the origin of a drug or drug residue.