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JPC - Journal of Planar Chromatography - Modern TLC
Authors: Vesna Glavnik, Breda Simonovska, Irena Vovk, Dragana Pavlović, Danijela Ašperger, and Sandra Babić

Validation of a method for the quantification of (−)-epicatechin and procyanidin B2 in chocolates is reported. After a simple preparation of the chocolate test solution, thin-layer chromatography (TLC) on high-performance thin-layer chromatographic (HPTLC) cellulose plates with n-propanol-water-acetic acid (20:80:1, ν/ν) and derivatization with 4-dimethylaminocinnamaldehyde (DMACA) were performed. Densitometry at 655 nm enabled accurate quantification of both analytes in chocolates. The milk chocolate sample which served for precision and recovery experiments contained 13.0 mg/100 g of (−)-epicatechin (relative standard deviation (RSD)) 5.8%, n = 6) and 13.2 mg/100 g of procyanidin B2 (RSD 4.2%, n = 6). Usable polynomial curves were 2–30 ng for (−)-epicatechin and 4–60 ng for procyanidin B2. The validated TLC method can be applied for routine quality control of the two major polyphenolic compounds in different chocolate samples.

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JPC - Journal of Planar Chromatography - Modern TLC
Authors: Mirko Prošek, Breda Simonovska, Alenka Golc-Wondra, Irena Vovk, Samo Andrenšek, Elizabeta Mičović, and Terezija Golob

HPTLC and HPLC-MS methods have been developed for quantitative determination of inulin in food products. Samples were applied to silica gel HPTLC plates and developed three times, twice with n -propanol-acetone-water, 45 + 30 + 25 ( v/v ), and the third time with n -propanol-acetone-water, 50 + 40 + 10 ( v/v ). Total development time was 150 min. Dried plates were dipped into DAP reagent for 10 s. After heating colored spots of the saccharides appeared. Quantitative evaluation of the colored spots was performed in transmission mode by means of a flatbed scanner and densitometer. The precision of measurements for the main inulin fractions was ±6.0%; the limit of quantitation ( LOQ ) varied from 0.1 to 1 µg per spot; and the ‘linear’ working range was between 0.5 and 4.0 µg per spot. The method was tested on real samples.

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Extraction of onion ( Allium cepa L.) with 80:20 ( v/v ) methanol-water in water by rotation planar extraction (RPE) and medium-pressure solid-liquid extraction (MPSLE) has been studied systematically. Rotation planar extraction was studied by use of an ExtraChrom separation instrument prototye. Only rotation planar extraction performed by use of the ExtraChrom enabled efficient extraction of dried onion. The equilibration time proved to be the most important variable in the extraction. The particle size of the sample had a variable effect on extraction efficiency, mainly because of the carbohydrates predominating in the extracts. It was possible to extract oligofructans with a degree of polymerization of up to 12, and these were the main components of the extract. Fructose, glucose, and saccharose, in total, accounted for 10% of the mass of the extract; their mass ratio in the extract was 3:1:6. After mild hydrolysis of the extract with oxalic acid only fructose and glucose were obtained. Although TLC screening of the extract before acid hydrolysis detected no flavonoids, one phenolic acid was observed. After acid hydrolysis with hydrochloric acid, quercetin could be detected.

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