Toxicological drug screening by thin-layer chromatography

A simple, cost-effective and rapid method for simultaneous determination of Strychnos nux-vomica alkaloids in blood and Ayurvedic medicines based on ultrasound-assisted dispersive liquid-liquid microextraction-thin-layer chromatography-image analysis

A simple, rapid, cost-effective and green analytical method is developed based on ultrasound-assisted dispersive liquid-liquid microextraction (US-DLLME) coupled to thin-layer chromatography (TLC)-image analysis for the simultaneous determination of two major alkaloids of Strychnos nux-vomica L i.e., strychnine and brucine. The method is composed of three steps, namely (i) US-DLLME by injecting a mixture of 100-μL chloroform (extraction solvent) and 1-mL methanol (disperser solvent) in 5 mL of aqueous sample, followed by ultrasonication and centrifugation, (ii) TLC of 20 μL of sedimented phase with methanol: ammonia (100:1.5, v/v) as the mobile phase and visualization under ultraviolet radiation (254 nm) and (iii) photography of TLC plate and quantification of spots by image analysis using freely available imageJ software (National Institute of Health, Bethesda, MD, USA). The limit of detection and limit of quantification for both alkaloids were found to be in the range of 0.12-0.15 and 0.36-0.48 μg/spot, respectively. The method was found to be linear in the range of 0.5-5 μg/spot with correlation coefficient (R2) of 0.995 and 0.997 for strychnine and brucine, respectively. The developed method was successfully applied for the determination of strychnine and brucine in Ayurvedic formulations and blood samples. The method does not require any sophisticated instrument and handling skills and can be adopted for rapid analysis of strychnine and brucine in forensic toxicological laboratories.

HPLC-DAD for analysis of different classes of drugs in plasma

A solid-phase extraction technique and HPLC-DAD method for drug screening in plasma were developed. This analytical method extracts and tests a number of drugs of different classes. The method includes; an acidic and basic Solid Phase Extraction (SPE) of plasma with C18 cartridges, a gradient elution of a modified cyano column with acidic buffer/acetonitrile eluent and a photodiode array ultraviolet (UV) detection. The drug screening procedure applied uses retention index and UV spectral data for the identification of compounds, may be appropriate in particular laboratory settings.

Planar chromatography at the turn of the century

An overview of the state-of-the-art of modern thin-layer chromatography (planar chromatography) is presented with emphasis on the complementary features of thin-layer and column liquid chromatographic separations. The reasons for selecting thin-layer chromatography for a particular analysis are identified by its attributes: a disposable stationary phase; simultaneous parallel separations; static detection free of time constraints; storage device for chromatographic information; all sample components are observed in the chromatogram. Future prospects for improved separation performance in TLC using zone refocusing, forced flow and electroosmotic flow methods are discussed as well as increasing zone capacity by using two-dimensional development and coupling to column chromatographic methods. Advances in coupling thin-layer chromatography with spectroscopic methods for structural elucidation are also considered. Finally, some predictions are made for how thin-layer chromatography will be practiced in the future.

Identification of drugs in autopsy liver samples by instrumental qualitative thin-layer chromatography

An instrumental thin-layer chromatographic (TLC) procedure is described for the identification of drugs with use of corrected RF values (hRcF) and in situ ultraviolet spectra. One hundred and eleven successive autopsy liver samples received from medical examiners were investigated by this technique and the results were compared to those obtained with a reference method. From the nineteen findings by the reference method, sixteen (84%) were correctly identified by the instrumental TLC method, using an hRcF pre-search with a window size of +/-7 units followed by a correlation search. In addition, one drug was identified correctly by correlation search only. There was no serious interference from endogenous substances, and a correlation value of about 0.9 is suggested as a limit to cut the hit list of candidates.