Thin-layer chromatographic determination of curcumine (turmeric) in spices

Summary The conditions for thin-layer chromatographic determination of curcumine in turmeric root powder and spice-mixtures have been optimized. Separation of the methanolic extract on silica gel thin-layer plates with chloroform-acetic acid (8020) gave the best results. The curcumine can be directly determined on the layer by fluorometric scanning, after conversion to rubrocurcumine with a mixture of boric acid and oxalic acid as spray reagent. Determination of the amount of turmeric root powder in spice mixtures by determining the curcumine content is only possible if the curcumine content of the turmeric root powder used is known because different turmeric root powders may have different curcumine contents.     

Thin-layer gel chromatography of 8-hydroxyquinoline metal complexes

Gel chromatographic behavior of 8-hydroxyquinoline (oxine, abbreviated HOx) complexes of zinc, copper, aluminum, gallium and indium has been investigated on thin layers of Styragel 60A and Merckogel OR-PVA 2000 mostly in chloroform and p-dioxan media. Except for the stable Cu(Ox)₂, the other oxinates exhibit either hydration or decomposition in gel-solvent-solute systems, which leads to strong retention or tailing on gel layers. An excess of 8-hydroxyquinoline present in solvents allows the oxinates to be stabilized, so that well-defined compact spots come out and migrate. For the Zn(Ox)₂ the formation of a self-adduct is strongly suggested on the basis of gel chromatographic behavior. Elution with the solvent containing pyridine also yields evidence of the adduct formation of zinc oxinate-nitrogen base.     

Comparison of optical in-situ scanning of conventional and high-performance thin-layer chromatograms

Conventional TLC, linear and circular HPTLC are compared by using In-situ reflectance measurements. Chromatographic resolution, time requirement and reproducibility of quantitative scanning of the different TLC methods are investigated by means of three separation problems: benzodiazepines, corticosteroids, polycyclic aromatic hydrocarbons. In all three application examples, which were chosen without prejudice, the circular developing mode with subsequent quantitative scanning showed certain advantages over the corresponding linear HPTLC techniques. These were in the case of

• Benzodiazepines: Better reproducibility of quantitative assessment.
• Corticosteroids: Better resolution and slightly better quantitative reproducibility.
• Polycyclic aromatic hydrocarbons: Chromatography considerably faster.

     

A new technique for the determination of polyamines: Overpressured ion-exchange thin-layer chromatography

Summary An overpressured, thin-layer ion-exchange, chromatographic method was developed for the separation of basic amino acids and natural polyamines. This technique, combined with video-densitometric evaluation, appeared to be suitable for the quantitative determination of polyamines in tissue extracts prepared without any previous purification.     

A simple device for the extraction of TLC spots: direct coupling with an electrospray mass spectrometer

A new device is described which allows the recovery of compounds from thin layer chromatograms in short times, within a small volume, and without contamination. This apparatus can be coupled online to an electrospray mass spectrometer, but can also be used with other detectors or for micropreparations.     

Quantitative determination of iron and copper in cotton material by TLC

Summary A TLC method for the separation of quantitative determination of copper and iron in cotton material is described. The optimal solvent system is 9:2:1 (v/v), ethanol-nitric acid-hydrochloric acid and the locating reagent is Na-diethyldithiocarbamate. Regression analysis shows that the most precise results can be obtained for the concentration range of 0.0400–0.0800 mg/ml of iron and copper.     

Optimization of the extraction conditions of amino acid dabsyl derivatives

Summary Moist buffered paper chromatography is proposed for the selection of the optimum conditions for the extraction of dabsyl derivatives of amino acids. It is shown for each individual acid and optimum pH value exists at which the distribution coefficient reaches a maximum. The optimum pH values can be easily determined from chromatographic data. The linear correlation between the static distribution coefficients and the R_M values permit the direct calculation of the distribution coefficient from the chromatographic data.     

A new reagent for the visualisation of N-alkylureas on TLC plates

Summary A new reagent for the visualisation of substituted ureas on TLC plates byin situ nitrosation is described. The procedure involves spraying the plates with two different reagents, and takes about five minutes. The method was tested on four different substituted ureas. A positive identification of nitroso compounds made byin situ nitrosation is discussed.     

Optimization of binary solvents in thin layer chromatography

ΔR_f, the separation between a pair of compounds on a thin layer chromatographic plate, can be predicted as a function of solvent composition for certain binary systems. This allows the prediction of optimum solvent composition for separating a mixture of compounds by thin layer chromatography. A new solvent polarity ranking, based on calculation of ΔR_f is described.     

Therapeutic drug monitoring by high performance thin-layer chromatography

Summary Methods for measuring concentrations of therapeutic drugs in blood serum have been devised which involve separation of the drugs by high-performance thin-layer chromatography (HPTLC) on silica gel followed by quantification by reflectance or fluorescence scanning. Aliquots of from 20 to 300 L serum are extracted with organic solvent. Portions of the extract containing approximately 1/4 of the drug present are deposited on a Contact Spotter (Clarke Analytical Systems), concentrated to a pin-point and applied to the HPTLC plate which is then developed and scanned.HPTLC permitted 12 samples and three standard solutions of drugs used to treat cardiac arrhythmias to be assyed for 6 drugs simultaneously, with scanning at a single wavelength. Results of these assays correlated well with those by EMIT^® immunoassays and by HPLC. No interference by other common drugs was observed. The total time required was two hours, making the work output esiily competitive with that of moderately rapid HPLC. Since sample preparation and quantification by scanning required only a small portion of this time, and the chromatography, which was time consuming, could be done on all the samples simultaneously, analysis of twice as many samples requires only an additional 1/2 hour. HPTLC thus offered the possibility of highly efficient mass production with relatively little capital equipment. Assay of chloramphenicol in serum, which in our laboratory requires fairly rapid turnaround of nnly a few samples at one time, required a similar length of time. Since standards and quality assurance samples could be assayed simultaneously, the analytical output was again comparable to that from a single HPLC instrument.Dedicated to Professor A. Zlatkis on the occasion of his 60th birthday.