Thin-layer chromatography Peroxides

Thin-Layer Chromatography. Thin-layer chromatography was used for many of the compounds which are of interest for either qualitative or quantative analysis. These techniques were used primarily as screening methods to supplement other analytical methods. For some brominated compounds such as TRIS, the detection system reported by Hahn (9) was applicable. This method is based upon the reaction of fluorescein with elemental bromine released through peroxide oxidation. An evaluation in our laboratory of this detection system indicated that semi-quantitative results... 

Procedures. Chromatographic Purification of Ozonization Products. Ozonization products from ethyl 10-undecenoate and 1-octene were chromatographed on silica gel columns (Baker) and eluted with 15 or 25% ether in petroleum ether (b.p., 30°-60°). Fractions were examined by thin-layer chromatography (TLC) on silica gel G Chroma-gram sheet eluted with 40% ether in petroleum ether. For development of ozonide and peroxide spots, 3% KI in 1% aqueous acetic acid spray was better than iodine. The spots (of iodine) faded, but a permanent record was made by Xerox copying. Color of die spots varied from light brown (ozonide) to purple-brown (hydroperoxide), and the rate of development of this color was related to structure (diperoxide > hydroperoxide > ozonide). 2,4-Dinitrophenylhydrazine spray revealed aldehyde spots and also reacted with ozonides and hydroperoxides. Fractions were evaporated at room temperature or below in a rotary evaporator. 

Analogous results were found in hydrogen peroxide oxidation of 2.6-di-tert-butyl-4(4-methoxyphenyl)-X -phosphorin 87. The crystalline 2-hydrophosphinic acid 88, m.p. 176-178 °C, on esterification with diazomethane, leads to a mixture of two diastereoisomeric esters, 89 E and 89 Z, which could be separated by thin-layer chromatography but not crystallized. 

The filtrate obtained from this reaction mixture is reduced to a volume of 15.0mL in a rotating evaporator and purified by means of thin layer chromatography (TLC) preparative plates of 1-mm thickness (Kieselgel P. F. Merck) eluant diethyl ether (5% vol) in light petroleum ether. The dark brown band of the complex is eluted with dry diethyl ether (peroxide-free). 

Gruber, M. P., Klein, R. W. and Foxx, M. Infrared and thin-layer chromatography determination of benzoyl peroxide degradation products in pharmaceuticals. J. Pharm. Sci. 58 566-569, 1969. 

A solution of the boronate 51 (38 mg, 0.10 mmol) in THF (3 mL) was added to hydrogen peroxide (30% solution, 5 mL) and the mixture was stirred at it for 12 h. NaHS04 (1 g) was then added and the product was extracted with CH2CI2 (2 X 25 mL). The combined organic extracts were washed with brine and dried (Na2S04). Removal of the solvent in vacuo and purification of the residue by preparative thin layer chromatography (hexane/ EtOAc, 3 1) provided the diol 52 (27 mg, 90%), m.p. 136 °C. 

Instrumental methods for analysis depend on the natme of peroxide. Gas chromatography is applicable where peroxides are thermally stable. It may also be applied as a pyrolytic decomposition technique in which the decomposition products are separated and quantified (Swem 1986). Liquid and column chromatography, thin-layer chromatography, and paper chromatography have been used for analyses of peroxides. 

It is well known that the phenol groups (which are bonded to the aporphine ring) and the benzylic amine function are responsible for the antioxidant and free radical scavenging activities of boldine [60], In addition, the presence of hydroxyl moieties in the chemical skeleton of boldine is responsible for its lipid peroxidation inhibitory activity [61], The level of boldine in the bark of boldo is more than 6% [62], Paper electrophoresis, voltammetric method, thin-layer chromatography and gas chromatography are common analytical methods for boldine determination [63],... 

Gresser et al. (1995) combined their PPF with VP and hydroxyapatite, crosslinking this mixture with benzoyl peroxide and DMT. Samples were allowed to crosslink at 37°C for 24 hours. These hardened samples were ground to analyze the amount of PPF and VP incorporated. The ground power was run in acetonitrile on reverse-phase thin layer chromatography plates, and developed with iodine vapor or ultraviolet light. Over 90% of the PPF was found to have been crosslinked in mixtures containing between 0.33 to 2 PPF/W ratios. The fraction of VP incorporated was dependent on the ratio of the two components. The fraction of PPF or VP incorporated was independent of the amount of hydroxyapatite, benzoyl peroxide, or DMT used. The VP monomer was found to add to poly( inyl pyrrolidinone) twice as often as it added to the fumarate double bond. 

Figure 5.12 Separation of amine antioxidants and antiozonants by one-dimensional thin-layer chromatography. Solvent benzene - acetone - concentrated ammonium hydroxide (100 5 0.1) development distance 15 cm indicator 4% benzoyl peroxide in benzene. 1 = N-phenyl-l-naphthylamine 2 = N-phenyl-2-naphthylamine 3 = p-(p-tolylsulfonylamido)-diphenylamine 4 = nonylated diphenylamines 5 = octylated diphenylamines 6 = octylated diphenylamines 7 = octylated diphenylamines 8 = 4,4-dimethoxydiphenylamine 9 = 4-isopropoxydiphenylamine 10 = 4"-isopropyl-aminodiphenylamine 11 = N, N-diisopropyl-p-phenylenediamine 12 = N,N -6i-sec-h xtyi-p-p)Lieny emdizTmne. Reproduced from [119]...

Brammer et al have described a method for determining dicumyl peroxide in polystyrene, which is not subject to interference by other organic peroxides or additives that may be present in the polymer. The dicumyl peroxide is extracted from the polymer with acetone and then separated from any other additives present by thin-layer chromatography on silica gel. The gel in the area of the plate containing dicumyl... 

Thin layer chromatography has also been applied to reactive organic peroxide residues such as tertiary butyl perbenzoate and benzyl peroxide in polystyrene (Method 34). 

Peroxide from 6 g polyethylene is concentrated into a 2 ml ether solution and 0.02 ml (20 ul) taken for thin-layer chromatography. 

As peroxy compounds differ from one another in solubility, it is obvious that several solvent systems are necessary for their separation. The following solvent systems have been found suitable (49—51) dimethylformamide/ /hexane to benzene ethylene glycol/hexane formamide/hexane -butanol-ethanol-water (45 5 50) or (10 10 1). For detection, sensitive down to 1 pg, the following sprays have been recommended (a) 0.1% p-amino-dimethylaniline hydrochloride and (b) a mixture of 3 ml of glacial acetic acid, 2 ml of a saturated potassium iodide solution, and 5 ml of starch solution. For the chromatography of organic peroxides on thin layers see (52, 53). 

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