Thin layer chromatography coupled with surface enhanced Raman scattering for rapid separation and on-site detection of multi-components

High performance thin layer chromatography with eluents containing SDS aided by UV- and Raman spectroscopy

The modification of non-polar silica gel plates by aqueous-organic solvent containing sodium dodecyl sulphate was investigated. The changes that occurred in the sorbent were examined using the Raman spectroscopy technique. The abovementioned technique was also involved in the investigation of carbamazepine-SDS complexes. The approach of applying the Raman spectroscopy into the investigation of the chromatographic behavior of SDS, carbamazepine and RP-18 W sorbent was presented for the first time. The effect of sodium dodecyl sulphate, SDS, concentration on the chosen drug used in neurodegenerative disorder (sulpiride, olanzapine, carbamazepine, trazodone, clomipramine, and pridinol) retention has been investigated. Such examination for these medicines has been presented for the first time for thin-layer chromatography system. Modified the mobile phase composition has resulted in the separation of the mixture containing all compounds. To confirm micellar forming, critical micelle concentration for SDS in the applied mobile phase was determined using two techniques, i.e., conductometric and spectrophotometric with azorubine as the indicator. The effect of surfactant on the solute zone shape by means of tailing and asymmetry factors has been determined. For four of the six investigated compounds, these factors have been close to 1.0. The separation efficiency measured by the height of the theoretical plate varies from 39 to 73 μm depending on the solute investigated. The method has been optimised regarding the quantitative analysis of investigated compounds, opening up new possibilities for drug analysis. In terms of the LOD values are in the range of 0.22 µg/spot to 1.67 µg/spot, whereas LOQ values are in the range of 0.66 µg/spot to 5.07 µg/spot for olanzapine and trazodone, respectively. Furthermore, the method was also applied for the quantitative analysis of the investigated compounds in pharmaceutical preparations. Such proceedings for RP-18 W TLC system containing SDS was shown for the first time. The new method has better or comparable concentration ranges regarding some of investigated compounds to those presented previously. Additionally, for the first time, a strategy involving various techniques (TLC chromatography supported by UV- and Raman spectroscopy and conductometry) for complex analysis of the separation system was presented, inspiring potential future research directions.

Coupling of chromatography with surface-enhanced Raman spectroscopy: trends and prospects

Surface-enhanced Raman spectroscopy is a powerful analytical technique for the determination of analytes with the advantages of sensitivity, portability, and simplicity, able to provide structural information for the identification of compounds. However, when it comes to the analysis of complex samples, matrix components may interfere with the analyte quantification. To overcome this shortcoming, a number of approaches have been proposed, such as extraction techniques. Among them, the coupling of chromatography with surface-enhanced Raman spectroscopy seems to be promising. It allows combining the advantages of both techniques, i.e., high efficiency of chromatographic separation and high sensitivity of surface enhanced Raman scattering detection, and makes possible simultaneous quantification of multiple analytes. The review summarizes the latest achievements in the combination of these techniques.

Dopamine-supported HPLC post-column derivatization to fluorescence: Simultaneous and sensitive detection of eight tea polyphenols

The effective differentiation and detection of multiple tea polyphenols are often challenging due to their subtle structural similarities. Although post-column derivatization HPLC strategies are commonly employed to distinguish multiple targets, the short physical distance between chromatographic column and detector limits reaction time, thereby reducing the derivatization efficiency. Dopamine (DA) reacts rapidly with resorcinol to form fluorescent azamonardine products, making fast fluorometric derivatization of tea polyphenols containing resorcinol motifs possible. In this study, a DA-driven rapid and post-column fluorescence derivatization method has been applied to sensitively detect eight tea polyphenols. This method is based on fluorescence derivatization and possesses low background interference, high sensitivity, and excellent reproducibility. Moreover, the practical application of this proposed fluorometric derivatization platform was further validated by simultaneous identification of multiple tea polyphenols in different tea samples. This work has great potential to become an alternative to the National Standard method for tea polyphenols determination.

Recent Progress of Molecularly Imprinted Technique for the Detection of Mycotoxins in Food

Mycotoxins are a group of toxic metabolites produced by fungi that infect agricultural products. Consuming mycotoxin-contaminated foods and feeds can cause various adverse health effects in humans and animals. Therefore, developing rapid and sensitive analytical methods for detecting mycotoxins is an urgent task. The molecularly imprinted technique is an advanced analytical tool for the specific recognition and selective enrichment of target molecules. For the development of rapid detection methods for mycotoxins, synthesized molecularly imprinted polymers (MIPs) can serve as specific recognition elements. By integrating MIPs with various sensing platforms, such as solid-phase extraction, electrochemical sensors, fluorescence sensors, surface-enhanced Raman spectroscopy, and surface plasmonic resonance sensors, remarkable progress has been made in the detection of mycotoxins in foods. This review focuses on the advances in the application of MIPs for the rapid detection of various mycotoxins over the past five years. The development of new MIP synthesis methods is categorized and summarized. Moreover, the future potential of MIP-based methods for mycotoxin detection is also discussed and highlighted.

Determination of multiple analytes in urine using label-free SERS coupled with simple sample pretreatments

BACKGROUND

A key restriction of label-free surface-enhanced Raman spectroscopy (SERS) in analysis of objects with complex composition (including with several target analytes) is the competition of mixture components for interaction with SERS-active surface. This leads to poor selectivity of the analysis of such mixtures (e.g., body fluids) and the need to use advanced sample pretreatment procedures such as HPLC or TLC. Therefore, this work aims to develop a set of simple and fast pretreatment steps (dilution, pH correction, etc.) to increase the sorption of the target analyte, reduce the sorption of admixtures, and prevent suppression of the target analyte SERS signal.

RESULTS

We have developed label-free SERS assay suitable for the determination of three analytes (methotrexate, cephalosporin antibiotic, and creatinine) in one real urine sample as a model matrix with complex and deviating composition. The choice of drugs is justified by the need to monitor their concentration in urine during joint drug treatment of cancer patients with concomitant bacterial infection, while monitoring creatinine concentration helps to evaluate kidney function of the patients. Additionally, three cephalosporin representatives were used in the study to maximize versatility of the assay. As a results, the optimized pretreatment steps enable to eliminate the negative influence of excess of interferences (including other analytes) and achieve precise (≤12 % RSD) and accurate (88-111 % recovery) determination of several analytes in the therapeutically relevant ranges: 300-3000 μg mL-1 for creatinine, 20-200 μg mL-1 for methotrexate and cephalosporins.

SIGNIFICANCE

Therefore, in addition to reporting a new SERS assay for the analysis of body fluids, this study clearly demonstrates the importance of taking into account competitive adsorption processes on the SERS substrate surface. We suggest making this practice mandatory when developing any label-free SERS assay because it enables to maximize the selectivity and accuracy of the analysis as well as to simplify the analysis procedure.

Liquid-liquid Phase Separation in Aging: Novel Insights in the Pathogenesis and Therapeutics

The intricate organization of distinct cellular compartments is paramount for the maintenance of normal biological functions and the orchestration of complex biochemical reactions. These compartments, whether membrane-bound organelles or membraneless structures like Cajal bodies and RNA transport granules, play crucial roles in cellular function. Liquid-liquid phase separation (LLPS) serves as a reversible process that elucidates the genesis of membranelles structures through the self-assembly of biomolecules. LLPS has been implicated in a myriad of physiological and pathological processes, encompassing immune response and tumor genesis. But the association between LLPS and aging has not been clearly clarified. A recent advancement in the realm of aging research involves the introduction of a new edition outlining the twelve hallmarks of aging, categorized into three distinct groups. By delving into the role and mechanism of LLPS in the formation of membraneless structures at a molecular level, this review encapsulates an exploration of the interaction between LLPS and these aging hallmarks, aiming to offer novel perspectives of the intricate mechanisms underlying the aging process and deeper insights into aging therapeutics.

Automated identification of pesticide mixtures via machine learning analysis of TLC-SERS spectra

Identification of components in pesticide mixtures has been a major challenge in spectral analysis. In this paper, we assembled monolayer Ag nanoparticles on Thin-layer chromatography (TLC) plates to prepare TLC-Ag substrates with mixture separation and surface-enhanced Raman scattering (SERS) detection. Spectral scans were performed along the longitudinal direction of the TLC-Ag substrate to generate SERS spectra of all target analytes on the TLC plate. Convolutional neural network classification and spectral angle similarity machine learning algorithms were used to identify pesticide information from the TLC-SERS spectra. It was shown that the proposed automated spectral analysis method successfully classified five categories, including four pesticides (thiram, triadimefon, benzimidazole, thiamethoxam) as well as a blank TLC-Ag data control. The location of each pesticide on the TLC plate was determined by the intersection of the information curves of the two algorithms with 100 % accuracy. Therefore, this method is expected to help regulators understand the residues of mixed pesticides in agricultural products and reduce the potential risk of agricultural products to human health and the environment.

Reversible polarity-switch of thin-layer chromatography by photo-induction with multi-regulation in spatial dimension

Generally, thin-layer chromatography always undertakes the indispensable role in rapid screening and identification of specific compounds. Stationary phase is the core part of thin-layer chromatography with fixed property, which leading to the limitations of separation mode of only regulating the composition of mobile phase. This work was an attempt to fabricate the unique photosensitive thin-layer chromatography to make up the above major drawback. 4-[3-(Triethoxysilyl)propoxy]azobenzene (azo-PTES) was synthesized as photosensitive modifier to fabricate the photosensitive stationary phase, and the transformation of cis-trans structure of azo-PTES proceeds along with polarity difference under 365 nm and 473 nm irradiation. Based on this, the proposed photosensitive thin-layer chromatography shows the reversible switch of polarity of stationary phase by photoinduction, followed by the deserved reversible separation behavior. Furthermore, multi-regulation in spatial dimension was achieved based on the high freedom of spatial regulation of photoinduction, which brings about the integration of stationary phase with different polarity, just by photoinduction. The concept of photosensitive thin-layer chromatography provides new idea for improving separation efficiency and developing multi-dimensional thin-layer chromatography on the one plate.