TLC/HPTLC and HPLC Methods for Monitoring Microbial Transformation Processes

JPC – Journal of Planar Chromatography – Modern TLC - TLC methods have been developed for monitoring microbial enantioselective reduction and regioselective oxidation. The work...     

Detection reagents used for on-plate identification of organic pesticides in biological samples with preliminary separation by TLC/HPTLC

Many specific and non-specific chromogenic spray reagents have been used to detect organic pesticides (organophosphorus, organochlorine, carbamates, and pyrethroids) on thin-layer chromatographic (TLC)/high-performance thin-layer chromatographic (HPTLC) plates. To realize high sensitivity and improved selectivity, several chromogenic reagents have been introduced. The physical properties of organic pesticides reported so far are also presented in tabular form. The colors produced on TLC plates due to reactions taking place between pesticides and spray reagents are illustrated in the form of chromatograms, and reaction mechanism is also presented.

     

New TLC/HPTLC commercially prepared and laboratory prepared plates: A review

Thin-layer chromatography (TLC) had its initial growth in the 1950s when TLC sorbents and devices for making TLC plates in the analytical laboratory became available. A resurgence in TLC use occurred when commercially prepared plates became available around 1965. Their advantage was greater reproducibility because of their uniformity and convenience of use. Having just passed the 50th anniversary of this date, TLC still finds wide application as a useful analytical tool throughout the world. The introduction of high-performance TLC (HPTLC)-prepared plates was also a welcome addition to the chromatography laboratory. Today, advances in TLC instrumentation that aid in sample application, plate development, qualification, and quantification continue to evolve and improve. The TLC/HPTLC plate manufacturers have continued to add new prepared plates to meet the greater demands for higher purity or special applications for these newer devices. More recently, researchers have experimented with new sorbents or preparation techniques that have resulted in special properties for thin-layer-prepared plates, particularly for use in TLC–MS applications. This article will discuss not only some classical TLC plates but also these newer thin layers, their advantages, and some of their applications.     

A simple method for carrier-free separation of77Br from metallic selenium

A simple method was developed for separation of bromine from metallic selenium. This method enables easy preparation of⁷⁷Br by proton bombardment of metallic selenium (enriched⁷⁷Se or⁷⁸Se). The method consists of heating the metallic selenium with H₂O to 300°C in a small autoclave for about three hours. The⁷⁷Br is distilled from the obtained solution after the addition of H₂SO₄+K₂Cr₂O₇. The step also removes the arsenic produced together with the selenium.     

A simple and universal method for the separation and identification of phospholipid molecular species

One of the major challenges in lipidomics is to obtain as much information about the lipidome as possible. Here, we present a simple yet universal high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) method to separate molecular species of all phospholipid classes in one single run. The method is sensitive, robust and allows lipid profiling using full scan mass spectrometry, as well as lipid class specific scanning in positive and negative ionisation mode. This allows high-throughput processing of samples for lipidomics, even if different types of MS analysis are required. Excellent separation of isobaric and even isomeric species is achieved, and original levels of lyso-lipids can be determined without interference from lyso-lipids formed from diacyl species by source fragmentation. As examples of application of this method, more than 400 phospholipid species were identified and quantified in crude phospholipid extracts from rat liver and the parasitic helminth Schistosoma mansoni.     

A simple electrochemical method for the determination of hydroxyl free radicals without separation process

Generally speaking, measurement of hydroxylated radical products of salicylic acid requires a fussy separation process. In this study, we describe a simple method to electrochemically detect hydroxyl radicals (*OH) using 4-hydroxybenzoic acid (4-HBA) as the *OH trap. The *OH is generated by the Fenton reaction from iron (II) sulfate and hydrogen peroxide in a phosphate buffer solution. Experimental results show that our method can detect the OH with high sensitivity without any separation process. The differential pulse voltammetric responses show a linear dependence on the concentration of *OH in a range of 2.0x10(-6) and 1.0x10(-3)M with a determination limit down to 5.0x10(-7)M. As a demonstration, the kinetics of the Fenton reaction was mapped by measuring the reaction product of hydroxyl radical trapped by 4-HBA. The result is in good agreement with that reported previously. All the results show that the present approach could provide a simple, inexpensive and promising method for biomedicine and iatrology.     

HPTLC separation of platinum metal 8-hydroxyquinolinates

High performance thin layer chromatography has been used to separate all the platinum metal 8-hydroxyquinolinates on polar stationary phases. The dependence of R_f values on the composition of mobile phases prepared from chloroform – tetrahydrofuran or chloroform – alcohol mixtures has been investigated. Retention was found to be partially dependent on alcohol chain length in chloroform – alcohol systems. The results obtained from TLC are dependent on the method of sample preparation used for the analyte.     

HPTLC fingerprint identification of commercial ginseng drugs - reinvestigation of HPTLC of ginsenosides

The optimized HPTLC of ginsenosides reported in this paper shows that the recommended solvent system has a higher resolution, greater spot capacity, and better reproducibility by comparison with the established ones in the previous literature. Detection and scanning in the fluorescence mode after visualization with 5% sulfuric acid/EtOH by the dipping technique improved and enhanced the sensitivity by a factor of nine compared to the commonly used absorbance made. Sample pretreatment by an adsorption clean-up step on a small alumina column followed by 1-butanol extraction instead of only a butanol-extraction step made the chromatogram clearer, caused less background contamination, and reduced the tailing of some ginsenosides spots. The ‘peak grouping’ method was effectively used in HPTLC fingerprint identification of various commercial ginseng medicines and the chromatograms of roots of ginseng (white and red; Panax ginseng), American ginseng (P. quinquifolium), and sanchi (P. notoginseng) obtained under recommended condition are perfectly recognizable.     

一种测定功能蛋白与其配体结合参数的简单方法

以羰基二咪唑法分别将牛血清白蛋白(BSA)和β2-肾上腺素受体(β2-AR)键合在大孔硅胶上,合成两种色谱固定相。采用直接进样法测定BSA与奥美拉唑、普萘洛尔和盐酸异丙嗪的结合常数及结合位点数,β2-AR与盐酸异丙肾上腺素、沙丁胺醇和去甲肾上腺素的结合常数及结合位点数。方法可用于功能蛋白与其配体分子相互作用的研究。     

一种测定功能蛋白与其配体结合参数的简单方法

以羰基二咪唑法分别将牛血清白蛋白(BSA)和β2-肾上腺素受体(β2-AR)键合在大孔硅胶上,合成两种色谱固定相。采用直接进样法测定BSA与奥美拉唑、普萘洛尔和盐酸异丙嗪的结合常数及结合位点数,β2-AR与盐酸异丙肾上腺素、沙丁胺醇和去甲肾上腺素的结合常数及结合位点数。方法可用于功能蛋白与其配体分子相互作用的研究。     

A validated HPTLC method for determination of trans-caryophyllene from polyherbal formulations

Formulations of traditional medicines are usually made up of a complex mixture of herbs. However, effective quality control methods in order to select materials of the right quality are lacking. 'Amukkara choornam' is a polyherbal Siddha formulation used for gastritis, spleen enlargement, leucorrhoea, hiccups, anaemia, tuberculosis and kappa diseases. Trans-caryophyllene is an important constituent present in the ingredients of this formulation. In a literature survey, it was found that there is no such method for the quantification of trans-caryophyllene except gas chromatography or gas chromatography-mass spectroscopy (GC-MS). So, a high performance thin layer chromatography (HPTLC) method was developed and validated for the quantification of trans-caryophyllene in amukkara choornam. Pre-coated silica gel 60F-254 plates (10 × 10 cm2) were used for the analysis. The solvent system consisted of toluene-ethyl acetatate (9 : 3, v/v), and trans-caryophyllene was detected at 260 nm. The developed method was validated for linearity (R2 = 0.9996 ± 0.0034), limit of detection (LOD) (0.101 ng), limit of quantification (LOQ) (0.639 ng), accuracy (% recovery = 97.19 ± 1.204), and precision (CV < 5%, for both intra-day and inter-day precisions). The levels of trans-caryophyllene were found to be 3.5-4.10 μg per gram of herbal products.     

A simple method for the visualization of the separated zones of sugars on silica-gel TLC plates without spray reagent

A simple procedure of visualization of the separated zones of sugars on silica gel TLC plates without spray reagent is described. The plate is placed into a glass chamber filled with n-hexane. The separated sugars are then seen as opaque zones.     

A rapid and simple HPTLC assay for therapeutic drug monitoring of capecitabine in colorectal cancer patients

Capecitabine is a prodrug of 5‐flurouracil, employed as a broad spectrum chemotherapeutic agent. It is also used as monotherapy or a combination chemotherapy agent for the treatment of colorectal cancer. Capecitabine is administered in combination with oxaliplatin and hence it is essential to determine that co‐administration does not affect its metabolism. To determine the plasma concentration of capecitabine a simple HPTLC method was developed and validated. Blood samples from 12 patients with colorectal cancer were collected and analyzed by the HPTLC method with a reference internal standard. Out of these 12 patients, six were treated with capecitabine monotherapy and another six were treated with capecitabine + oxaliplatin combination therapy. The results of analysis indicated that there was no significant drug–drug interaction and the co‐administration of oxaliplatin did not affect the metabolism of capecitabine. This method is sensitive, robust and specific and allows analysis of multiple samples simultaneously, making it suitable for therapeutic drug monitoring of capecitabine.     

Evaluation of various biological activities of natural compounds by TLC/HPTLC

Abstract

Over the last years, thin layer chromatography (TLC) has become an increasingly important tool in the analysis of natural compounds, being used not only as a simple method of separation, identification, and quantitative determination of natural constituents, but also as a method for evaluating the potential applications of the separated compounds, different bioassays being compatible with TLC. This is due to the TLC advantages, of which could be mentioned: the possibility to simply, quickly, and flexibly analyze many samples in parallel, without the need for special steps of sample purification, obtaining visual results, and the possibility of multiple detections, all of these being achieved at very low costs. Considering these, the aim of this study is to give an overview on the application of TLC in evaluation of different biological activities of natural compounds, focusing on antioxidant, enzymatic, antimicrobial, and hormonal activities.