Thin layer chromatography phenolic acids

Types of thin layers. The phenolic acids arising from clinical studies (88) have been examined by TLC on cellulose (88-90) and with cellulose on Silufol (91). TLC was considered superior to paper chromatography. The identification of phenolic acids in varieties of Ribes nigrum has been described (IS), and separation of phenolic acids fix>m plant material or silica gel G and quantitative analysis with spectrophotometry (92). Phenolic acids extracted from plants were best separated on silica gel G with chloroform-ethyl acetate-formic acid (5 4 1) (8). TLC on silica gel combined with scanning spectrophotometry was used to separate nine phenolic acids in wine with hexane-ethyl acetate-formic acid (15 9 2) (93) as the preferred of the 10 solvents examined. Twenty naturally occurring phenolic acids were separated by a combination of one- and two-dimensional TLC and development with three solvents (94) and phenolic acids (and some phenols) related to humic acid examined on alumina with water as solvent (94a). Silica gel F-254 (Silica-Rapid-Platten Woelm in... 

Z. Males and M. Medic-Saric, Investigation of the flavonoids and phenolic acids by thin layer chromatography. J.Plan. Chromatogr.—Mod. TLC 12 (1999) 345-349. 

Medic-Saric M, Jasprica I, Smolcic-Bubalo A and Momar A, Optimization of chromatographic conditions in thin layer chromatography of flavonoids and phenolic acids. Croatica ChemicaActa 77 361-366 (2004). 

PGL-I, homogeneous by thin-layer chromatography, through reverse-phase HPLC showed heterogeneity based on fatty acid content, and PD-MS analysis demonstrated the existence of the C3o,C3o mycocerosate glycolipid, the C32,C32 species, and the species.27 Two other minor phenolic glycolipids isolated from M. 

In addition to the need to monitor known problematic compounds, newer compounds are being identified as potential threats to humans and as such need to be monitored in the atmosphere. For example, researchers reported (10) that several chemical and instrumental analyses of HPLC fractions provided evidence for the presence of /V-nitroso compounds in extracts of airborne particles in New York City. The levels of these compounds were found to be approximately equivalent to the total concentrations of polycyclic aromatic hydrocarbons in the air. Since 90% of the N-nitroso compounds that have been tested are carcinogens (10), the newly discovered but untested materials may represent a significant environmental hazard. The procedure involved collecting samples of breathable, particulate matter from the air in New York City. -These samples were extracted with dichloro-methane. Potential interferences were-removed by sequential extractions with 0.2 N NaOH (removal of acids, phenols, nitrates, and nitrites) and 0.2 N H2S04 (removal of amines and bases). The samples were then subjected to a fractional distillation and other treatments. Readers interested in the total details should consult the original article (10). Both thin-layer chromatography (TLC) and HPLC were used to separate the compounds present in the methanolic extract. 

Chitin has been used as the stationary phase to separate mixtures of phenols, amino acids, nucleic acid derivatives, and inorganic ions by thin layer chromatography. Also chitin has been used to prepare affinity chromatography columns to isolate lectins and determine their structure. 

The phenylthiohydantoins may be identified directly by thin layer chromatography or gas-liquid chromatography (see below). Alternatively, they can be hydrolyzed at 140°C in 5.7 N glass-distilled HCl in vacuo (see 2.1.2 for other details) in the presence of phenol (1 drop of 5 % phenol in water) to regenerate the amino acid, which can be identified with an analyzer or by pH 1.9 electrophoresis. The regeneration is not quantitative, and several amino acids, particularly serine and threonine, are usually destroyed completely. 

Silica gel is the most extensively used adsorbent in thin layer chromatography because it leads to excellent, uncomplicated separations. It can be successfully employed for both qualitative and quantitative thin layer chromatographic analyses. It is usually used as a stationary phase in separations and analysis of alkaloids, various organic acids (especially amino acids and their derivatives), steroids, lipids, vitamins, plant pigments, pesticides, drugs, carbohydrates, phenolic substances, etc. 

Ersser, R.S. Oakley, S.E. Seakins, J.W.T. Urinary phenolic acids by thin-layer chromatography. Clin. Chim. 

J. H. P. Tyman, Phenols, aromatic carboxylic acids, and indoles, in Handbook of Thin-Layer Chromatography (J. Sherma and B. Fried, eds.), Marcel Dekker, Inc., New York, 1996, pp. 877-920. 

The 2-D TLC was successfully applied to the separation of amino acids as early as the beginning of thin-layer chromatography. Separation efficiency is, by far, best with chloroform-methanol-17% ammonium hydroxide (40 40 20, v/v), n-butanol-glacial acetic acid-water (80 20 20, v/v) in combination with phenol-water (75 25, g/g). A novel 2-D TLC method has been elaborated and found suitable for the chromatographic identification of 52 amino acids. This method is based on three 2-D TLC developments on cellulose (CMN 300 50 p) using the same solvent system 1 for the first dimension and three different systems (11-IV) of suitable properties for the second dimension. System 1 n-butanol-acetone -diethylamine-water (10 10 2 5, v/v) system 11 2-propanol-formic acid-water (40 2 10, v/v) system 111 iec-butanol-methyl ethyl ketone-dicyclohexylamine-water (10 10 2 5, v/v) and system IV phenol-water (75 25, g/g) (h- 7.5 mg Na-cyanide) with 3% ammonia. With this technique, all amino acids can be differentiated and characterized by their fixed positions and also by some color reactions. Moreover, the relative merits of cellulose and silica gel are discussed in relation to separation efficiency, reproducibility, and detection sensitivity. Two-dimensional TLC separation of a performic acid oxidized mixture of 20 protein amino acids plus p-alanine and y-amino-n-butyric acid was performed in the first direction with chloroform-methanol-ammonia (17%) (40 40 20, v/v) and in the second direction with phenol-water (75 25, g/g). Detection was performed via ninhydrin reagent spray. 

Bahorun and colleagues describe the use of thin-layer chromatography (TLC) to determine total proanthocynidins, phenol, and flavonoid content of hawthorn extracts. High-performance liquid chromatography (HPLC) analysis using a UV detector at 280 nm for proanthocyanidins and phenolic acids, and 360 nm for flavonoids is also described (Bahorun et al., 1996). 

Kappenberg [68] derivatized sample solutions of inflorescenses of hawthorn and lime (Tilia sp.), among other species, with dansylchloride (5-dimethylamino-l-naphthalinsulfonyl chloride) prior to thin layer chromatography on silica. Detection is based on the measurement of fluorescence at 365 nm. Under the applied experimental conditions phenolic acids and flavonoid glycosides remained at the start, whereas derivatives of B-type procyanidin dimers were developed as a single spot. The sensitivity was reported to be ten times higher compared to the vanillin condensation products. Drawbacks of this method are that it is sensitive to light and that so far, no studies on reaction kinetics of individual procyanidins have been performed. 

Powdered neutral imprinted polystyrene obtained at [H2O] = 2.78 M and [AOT] =0.2M, and having a surface area of 19.4m /g, was used for the preparation of a thin-layer chromatography plate and the separation of nitrobenzene, phenol, anUine, benzoic acid, and nitrophenol positional isomers. The plate showed fairly different Rf values for all these compounds, while the selectivity of a commercial sihca plate was found to be much worse [365]. 

Chitosans find a wide variety of applications in chromatographic separations. The presence of free amino and hydroxyl groups in chitosan makes it a useful chromatographic support. Chitosan can be used in thin layer chromatography for separation of nucleic acid and solid phase extraction of phenols and chlorophenols [69]. 

The first uses of micellar phases by Armstrong were done in GPC and thin layer chromatography (TLC). This was described in Chapter 3. TLCwas a useful tool for the determination of solute partition data in micellar systems. The micellar partition coefficient, Pv, the solute-stationary phase interaction coefficient, P s, and the micellar binding constant, Kd, could be obtained from the solute-Rf parameters with an equation very similar to eq. 13.5 [22]. A number of solutes were separated by micellar TLC such as phenols and dyes [22], indicators, caffeine, biphenyl, naphthol and benzamide [23], PAHs and amino acids [24], vitamins [25] or fluorescein derivatives [26]. The low cost, low toxicity, peculiar selectivity and ease of... 

Developers A = 2% formic acid B = 20% potassium chloride C = isopropyl alcohol mmonium hydroxide-water (8 1 1) D = 10% acetic acid. Source From Thin-layer chromatography of some plant phenolics, in J. Chromatogr. ... 

A wide variety of stationary phases have been used to separate substituted monocyclic phenols and phenolic acid compounds and their derivates by thin-layer chromatography (TLC). In particular, the composition of phenolic acids and flavonoids in leaves, roots, and fruits of several plants and in natural products has been extensively studied by the two-dimensional TLC by using cellulose or silica gel plates in one direction and silanized silica gel in the second direction. Quantitative determinations of flavonoids components of plant extracts were widely performed. 

Medic-Saric, M. Males, Z. Selection of an optimal set of solvents in thin-layer chromatography of flavonoids and phenolic acids of Lavandulae flos. Pharmazie 1999, 54 (5), 362-364. 

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