Quantitation in high-performance micro-thin-layer chromatography

Improved separation of lipid esters by thin-layer chromatography

Methods for the separation of ethyl- and 2-chloroethyl esters of fatty acids using argentation thin-layer chromatography (TLC) and linear and circular reversed-phase TLC are described. An argentation TLC method for the separation of cholesterol esters is also described. The separation is based on the degree of unsaturation in the fatty acid moiety. In all instances good and reproducible resolution was achieved by unidirectional single developments at room temperature with reduced analysis times (9 min for argentation TLC, 7 min for circular reversed-phase TLC).

Thin-layer chromatography of mycotoxins

TLC has become an extremely powerful, rapid and in most instances inexpensive separation technique in mycotoxicology. This review presents achievements of its applications in this field. General technical aspects of the TLC of mycotoxins that are discussed include extraction and clean-up procedures, adsorbents and solvent systems, detection methods, two-dimensional TLC, high-performance TLC (HPTLC), quantitation and preparative TLC (PLC). Special applications of TLC deal with multi-mycotoxin analyses and with structurally related or individual mycotoxins (aflatoxins, sterigmatocystins, versicolorins, ochratoxins, rubratoxins, patulin, penicillic acid, mycophenolic acid, butenolide, citreoviridin, trichothecenes, cytochalasans, tremorgenic toxins, epipolythiopiperazine-3,6-diones, hydroxyanthraquinones, zearalenone, citrinin, secalonic acids, cyclopiazonic acid, PR toxin, roquefortine, xanthomegnin, viomellein and naphtho-gamma-pyrones).

A quantitative densitometric method for the rapid separation and quantitation of the major tissue and lipoprotein lipids by high-performance thin-layer chromatography. I. Sample preparation, chromatography, and densitometry

A rapid method for the separation and quantitation of the major lipids of tissues and lipoproteins by automated high-performance thin-layer chromatography is presented. Solvent systems for one-dimensional separation of neutral lipids, of cholesteryl esters, and of phospholipids are described. Separated lipids are measured following treatment with methanolic sulphuric acid containing manganese chloride and scanned in fluorescence or absorption mode. Absolute quantitation is obtained by the use of an internal standard and by references to standards for each lipid run on the same plates as samples. The method described here is particularly suitable for the rapid quantitation of small amounts of lipid (0.01-0.02 nmol per sample), for example in tissue culture studies; 100 micrograms of fibroblast or macrophage protein are sufficient for complete lipid analysis. The coefficients of variation due to the sample preparation, application to the plates and densitometry are in the range 7.2-9.1%. The method was compared with enzymatic determinations for cholesterol and gave correlation coefficients of 0.95 for total cholesterol and 0.91 for unesterified cholesterol. Phospholipid estimation was compared with large-plate thin-layer chromatography and phosphorus analysis and gave correlation coefficients of 0.90 for phosphatidylcholine and 0.89 for sphingomyelin.

[Chromatographic determination of ointment bases and emulsifying agents in European and German pharmacopoeias]

The ointment bases Lanolinum, Lanae alcoholum unguentum, Zinci unguentum, Polyethylenglycoli unguentum, Unguentum leniens and Unguentum emulsificans, and the emulsifying agents Glyceroli monostearas, Polyethylenglycoli 400 stearas and Polysorbatum 20, 60, 80 were identified by HPTLC and their most important components were determined quantitatively by application of HPLC. The proposed methods of identification are more specific than those described in the monographs of the pharmacopoeias. The obtained results were compared with the nominal values listed in both pharmacopoeias as assays of these bases and emulsifiers are not mentioned, except for glyceroli monostearas.

Simultaneous determination of antiarrhythmia drugs by high-performance thin-layer chromatography

A method is described for the determination of antiarrhythmia drugs in serum by high-performance thin-layer chromatography. Baseline separations are achieved for all the drugs and clozapine, an internal standard, in two developments with solvents of different polarity. Lidocaine and diphenylhydantoin are scanned at 220 nm after the first development. Procainamide, propranolol and quinidine are scanned at 290 nm after the second development. The relative standard deviation of the determination varies between 3 and 14% depending on the nature of the drug and its concentration.

[Comparative chromatographic analyses of s-triazines (author's transl)]

The applicabilities of gas chromatography (GC), high-performance liquid chromatography (HPLC), thin-layer chromatography (TLC) and high-performance thin-layer chromatography (HPTLC) for residue analysis of s-triazine herbicides are compared. With the conditions discussed the detection limit for the 14 s-triazines was determined as follows: 0.02-0.03 ng in GC alkali flame-ionization detection, 0.8 ng in GC flame-ionization detection, 1 ng in HPLC (UV detection), 3-5 ng in HPTLC (UV detection) and 8-13 ng in TLC (UV detection). The linear range in GC (AFID) was 10(4) whereas in the three liquid chromatographic methods it was 10(2). The reproducibility with a confidence limit of P = 95% had a coefficient of variation of +/- 5%. In routine analysis requiring a large number of separations HPTLC has advantages, because the time for a single separation is only 40 sec.

High-performance thin-layer chromatographic determination of psychopharmacologic agents in blood serum

High-performance thin-layer chromatography affords a rapid, sensitive method for determination of psychopharmacologic agents in blood serum samples. Quantitation of the representative drugs chlorpromazine, amitriptyline, nortriptyline, imipramine, and desipramine at levels as low as 5 ng/ml is demonstrated by scanning the developed thin-layer plates with a chromatographic spectrophotometer in the ultraviolet absorption mode. Neither derivatization prior to, nor color development after chromatographic separation is required to achieve sensitivity and reproducibility of determinations.

Quantitation with high-performance thin-layer chromatography and programmed multiple development with high-performance micro-thin-layer material for drug analyses in biological fluids

The programmed multiple development thin-layer chromatography (PMD-TLC) technique was compared with the conventional chromatographic technique on both normal and HPTLC plates. The potency of this high-performance TLC is illustrated and discussed by means of the data obtained with the determination of digitoxin in human serum. Improvement of the efficiency of TLC, resulting in a better resolution and sensitivity with PMD-TLC using using HPTLC plates, makes this high-performance TLC technique comparable to high-performance liquid chromatography. This TLC approach might lead to a sensitive, rapid, selective and simply assay for routine serial analyses and, because of its specificity and flexibility, it may facilitate drug interaction studies.