Quantitative Thin-layer Chromatography Research Articles

Solvent Effects on the Precision of Sample Application in Quantitative Thin-Layer Chromatography

Abstract The use of non-polar solvents for sample application in quantitative thin-layer chromatography (TLC) was shown to have a marked effect on the precision of the analytical technique when polar compounds were applied to silica gel plates. Increasing the polarity of the application solvent allowed competitive binding of the solvent molecules to silica, thereby deactivating the silica at the origin. Studies showed that the coefficient of variation for TLC assays were substantially reduced by altering the polarity of the application solvent.

ABNORMAL INTESTINAL PERMEABILITY TO SUGARS IN VILLOUS ATROPHY

Intestinal permeability to a monosaccharide and a disaccharide was compared by simultaneous measurement of the urinary excretion of L-rhamnose and lactulose after oral ingestion of an hypertonic solution containing both sugars. Urine samples were analysed for sugar content by quantitative thin-layer or paper chromatography. Results in thirteen patients with untreated villous atrophy were compared with those in twelve healthy volunteers. Urinary L-rhamnose excretion was significantly decreased (-40%, p<0·02) in patients with villous atrophy, whereas lactulose excretion was paradoxically and significantly increased (+345%, p<0·01). The median value of the lactulose/L-rhamnose urinary excretion ratio was sevenfold higher in the patients with villous atrophy; there was no overlap of values for patients and volunteers (p<0·01). It is postulated that reduced L-rhamnose urinary excretion in untreated villous atrophy is due to a decreased absorptive area in the small bowel, whereas increased lactulose excretion indicates leakiness of the abnormal mucosa to larger polar molecules.

Quantitative thin-layer chromatography and mass spectrometry of isatinylmethyl esters of carboxylic acids

Quantitative thin-layer chromatography and mass spectrometry of isatinylmethyl esters of carboxylic acids

Determination of sulphur-containing amino acids by quantitative ion-exchange thin-layer chromatography

Determination of sulphur-containing amino acids by quantitative ion-exchange thin-layer chromatography

Quantitative thin-layer chromatography: thin-film fluorescence scanning analysis of adriamycin and metabolites in tissue

A rapid, non-hydrolytic thin-film fluorescence scanning method is described for the quantitation of adriamycin and metabolites in tissues. Adriamycin, with daunomycin added as the internal standard, was extracted from tissue homogenate which contained 500 μg of oxalic acid, with ice-cold 0.5 N hydrochloric acid-85% isopropanol, separated by thin-layer chromatography, and quantiated in situ via a fluorescence scanning technique. This method has a sensitivity to 0.05 μg per gram of tissue.

Determination of indomethacin in plasma and urine by direct quantitative thin-layer chromatography.

Determination of indomethacin in plasma and urine by direct quantitative thin-layer chromatography.

Comparative studies on the nature of purified cytomembranes of the rabbit parotid gland

Centrifugation procedures have been evolved for isolating purified samples of rough endoplasmic reticulum, Golgi, zymogen granule and plasmalemmal membranes from homogenates of rabbit parotid gland tissue. The purification process was monitored using morphometry and enzyme and chemical marker assays. The membrane preparations were analysed by sodium dodecylsuphate (SDS) polyacrylamide gel electrophoresis, quantitative phospholipid thin layer chromatography and by enrichment studies. The results were used to evaluate various possible general models for the behaviour of membranes during the secretory cycle of parotid acinar cells.

Quantitative thin layer chromatography for the analysis of skin surface lipids. A time-saving method using a new TLC plate.

Recently a new thin layer chromatography plate (Whatman LK 6D) became available which is extremely easy to handle and permits highly reproducible qualitative and quantitative analysis. This plate proved to be of great value for the investigation of skin surface lipids. The use of a fatty acid methyl ester as an internal standard makes it unnecessary to employ additional gravimetrical or photometrical methods for quanitative lipid analysis. The method presented in this paper is simpler and requires much less time than alternative procedures and allows a large number of lipid samples to be processed simultaneously.

Radiotracer investigation of a quantitative thin-layer chromatographic separation

Radioactive labelling has been shown to be a powerful technique for investigating quantitative thin-layer chromatography. The dispensing of small volumes by several appliances has been shown to be precise but biased to the extent of several percent by “creep back” of the dispensed solution on the needle of the syringe. Losses in the thin-layer chromatographic separation and recovery of phthalimide once the solution had been dispensed totalled approximately 3%. These losses were attributed to a residue at the site of application to the plate, underestimating the size of the developed spot and the failure of a fraction of the phthalimide to elute.

Determination of alkaloids from Lupinus polyphyllus by quantitative thin-layer chromatography

Determination of alkaloids from Lupinus polyphyllus by quantitative thin-layer chromatography

Determination of amitriptyline and nortriptyline in human plasma by quantitative thin-layer chromatography

A thin-layer chromatographic method for simultaneous determination of amitriptyline (AT) and nortriptyline (NT) in human plasma is described. Both substances are extracted from biological material by means of a single extraction. The extract is evaporated until dry and the residue quantitatively applied to a silica gel thin-layer plate. AT and NT are separated from interfering plasma components by chromatography. The spots are visualized by nitration, reduction and coupling with N-(1-naphtyl)ethylenediamine on the plate. The intensity of the azo-dyes formed can be measured densitometrically. Using 1 ml of plasma, the sensitivity limit was 0.5 ng/ml for both substances. About 10–15 plasma samples can be analysed per day. The method is applicable to pharmacokinetic studies after a single oral dose of 25 mg AT as hydrochloride in man.

Quantitative thin-layer chromatography of carbohydrates using pentavalent vanadium in sulphuric acid : Determination of mixtures of d-Fructose, d-Glucose and sucrose

Pentavalent vanadium in sulphuric acid can be used for the quantitative analysis of sugars. The yellow pentavalent vanadium is reduced by carbohydrates to the blue tetravalent form, and either the consumption of vanadium(V) or the amount of vanadium(IV) formed can be measured. For model studies, different d-fructose- d-glucose-sucrose mixtures were used. The monosaccharides were separated from the disaccharide by thin-layer chromatography. Owing to the great difference in reactivity between aldohexoses and ketohexoses, d-fructose and d-glucose can be determined separately without prior separation. The method enables 10 μg of each sugar to be determined.

Determination of bromazepam in plasma by quantitative thin-layer chromatography

A method for determination of bromazepam (I) in plasma on thin-layer plates is described, which is highly specific and sensitive. After extraction from plasma, bromazepam is separated from interfering constituents by thin-layer chromatography. The quantitation of the spots can be performed in two different ways. Either it is possible to measure directly the UV reflectance on the plate, or bromazepam is hydrolyzed to 2-amino-5-bromobenzoyl-pyridine (ABBP, II) on the thin-layer plate, diazotized and coupled with N-(1-naphthyl) ethylenediamine to form an azo-dye, which can be evaluated densitometrically. The recovery from plasma was found to be above 90%, the sensitivity of both methods was about 5 ng of bromazepam per cm3 of plasma using 0.5 cm3. The relative standard deviation of both procedures was ±6%. In a series of plasma samples the concentration of bromazepam was determined by the thin-layer procedures described and by GLC with an electron capture detector. The different methods gave similar results, but the thin-layer chromatographic methods are easier to perform.

Investigations on acne vulgaris related to erythromycin stearate as a model substance

SummaryThe mechanism by which Propionibacterium acnes induces inflammatory lesions in acne vulgaris is still unknown. To investigate the effect of erythromycin stearate in acne vulgaris, the composition of the skin surface lipids was analyzed before, during and after treatment in 17 patients given 500 mg daily for 1 week and 250 mg daily for 2 months. The clinical anti-inflammatory effect was also evaluated. Quantitative thin-layer chromatography showed that the fatty acid fraction of the skin surface lipids decreased significantly in all patients during treatment. The clinical anti-inflammatory effect was good in 14 of the 17 patients. ATR-infrared spectroscopy showed that the clinical effect precedes the detectable reduction in fatty acids in the skin surface lipids. Even if a toxic effect of the fatty acids is responsible for the inflammation in most patients, an allergy to the fatty acids in some cases cannot be excluded. Sensitization tests on guinea-pigs showed that short-chained and middle-chained fatty acids, especially, are highly allergenic. The effect of erythromycin stearate on the lipase activity was also studied in a model system (purified pancreatic lipase). The enzyme activity was not affected by exposure to the drug. Consequently, the effect of erythromycin stearate on P. acnes was evaluated in acne patients, the bacteria being identified by aid of gas-chromatography. All the strains isolated were highly sensitive to erythromycin stearate before and after treatment. Semi-quantitative screening of P. acnes isolates on Tween 80 and tributyrine agar dishes after erythromycin stearate therapy indicated that P. acnes strains lacked lipolytic activity. However, in none of the patients' pustules or cysts was P. acnes completely inhibited. Sub-culturing demonstrated no significant quantitative decrease in the numbers of P. acnes after 1 week of therapy but did so after 4 weeks. Erythromycin stearate, therefore, may decrease the viability and numbers of P. acnes.

Free fatty acids in the early inflammatory papule of acne vulgaris.

Summary The role of free fatty acids (FFA) in the pathogenesis of acne is disputed. Several studies have failed to show an increase in FFA concentration in skin surface lipids (SSL) from acne patients. It has been suggested that a marked increase in FFA concentration in a single sebaceous follicle may lead to the inflammatory lesion in acne, and because SSL samples are usually taken from a large area, this localized increase would be swamped by the lipid from the surrounding normal follicles. We therefore used a micro-cylinder method to obtain SSL from early acne papules and we compared this with SSL from nearby ‘normal’ skin in 19 patients. The samples were analysed by quantitative thin layer chromatography. We found no significant difference in the mean FFA concentration in SSL obtained from acne papules and normal skin. Our findings do not support the idea that the inflammation of acne is due to an increase in FFA concentration in skin lipids.

Modification of quantitative thin-layer chromatography by elution

Modification of quantitative thin-layer chromatography by elution

Quantitative TLC Analysis of Amine Antioxidants in High-Temperature Jet Engine Lubricants

Abstract : A quantitative thin-layer chromatography (TLC) method with a relative standard deviation of four percent is described for the analysis of commonly used amine antioxidants in high-temperature jet engine lubricants. The method is convenient in that after development of the plates, the components develop characteristic visible colors suitable for analysis. (Author)

Determination of prothionamide and its sulphoxide metabolit in physiological fluids by quantitative thin-layer chromatography

Determination of prothionamide and its sulphoxide metabolit in physiological fluids by quantitative thin-layer chromatography

Method for the separate determination of the main glycoalkaloids of the genusSolanum L. by quantitative thin-layer chromatography

Method for the separate determination of the main glycoalkaloids of the genusSolanum L. by quantitative thin-layer chromatography

Continuous quantitative thin-layer chromatography of oligosaccharides

Continuous quantitative thin-layer chromatography of oligosaccharides