Ethanol vapour, detection

With this equipment many small molecules are detectable (Table 1). Some of them are particularly important in fruit analysis. Water vapour detection allows one to monitor respiration processes ethanol and especially acetaldehyde measurements permit one to follow the onset of fermentation (Bijnen 1995) ethane is taken as an indicator of cell membrane damage. It should be noted that periodic release of methane by cockroaches is investigated in detail with this setup (Bijnen 1995). 

We recall from Chapter 5 how the intensity of a smell we detect with our nose is proportional to the vapour pressure of the substance causing it. The vapour pressure of ethanol is P(ethanoi), its magnitude being proportional to the mole fraction of ethanol in the brandy brandy typically contains about 40 per cent (by volume) of alcohol. Although adding table salt does not decrease the proportion of the alcohol in the brandy, it does decrease the apparent amount. And because the perceived proportion is lowered, so the vapour pressure drops, and we discern the intensity of the smell has decreased. We are entering the world of perceived concentrations. 

Figure 3 High-performance thin-layer chromatographic separation of ten rare earths (as nitrates). Sample, 1 pg each of rare earth layer, silica, impregnated with ammonium nitrate prior to the separation mobile phase, 4-methyl-2-pentanone/terahydrofu-ran/nitric acid/2-ethylhexylphosphonic acid mono-2-ethyl hexyl-ester 3 1.5 0.46 0.46 developing distance, 5 cm detection reagent, (1) spray of saturated alizarin solution in ethanol, (2) ammonia vapour, (3) gentle heating. (After Wang QS and Fan DP (1991) Journal of Chromatography 5S7 359.)...

Polyamine products of reaction between ethylene dichloride and ammonia can be separated on silica gel G layers, using concentrated ammonium hydroxide-ethanol (66 + 33) the following hJ /-values have been obtained [22] CgHgNg (ethylenediamine) 44 C4H13N3 41 CeHj8N4 32 C8H23N5 27. Iodine vapour was used for detection. 

Detection The layers are held over NH3 vapour and then sprayed with a solution of 0.6 g 8-hydroxyquinoline in 100 ml 60% ethanol. The spots are evaluated in UV light of 366 nm (Table 218). 

Detection Spraying with 0.5% 8-hydroxyquinoline in 60% ethanol, followed by exposure to NH3 vapour and inspection in UV light of 365 nm. 

Detection 1 group 0.5% aqueous NagS solution 2 group saturated solution of alizarin in 96% ethanol. The layers are exposed to NH3 vapour after spraying. 

Fuse about 0 5 g of the substance with 2 g of potassium hydroxide in a hard-glass test-tube, or better, in a nickel crucible for 10 minutes. A simple sulphonamide evolves ammonia, while a substituted sulphonamide liberates an amine, the vapour of which may be detected by means of filter-paper moistened with saturated ethanolic 2,4-dinitrochlorobenzene solution a strong yellow colour is a positive test. 

Uhde and co-workers [34, 35] have studied the migration of 4,4 -thiobis-6-tert-butyl-w-cresol (Santonex R) from plastics utensils into sunflower seed oil. Sunflower seed oil that had been stored in vessels of polyethylene containing this antioxidant was diluted (3 5) with pentane and extracted with acetonitrile containing 5 % of water. The concentrated acetonitrile extract (or an ethanol solution of the residue on evaporation) was snbjected to thin-layer chromatography on Kieselgel with hexane-ethyl acetate (10 3) as solvent. To detect the antioxidant (down to 0.1 ppm) the plate was sprayed with 3,5-dichloro-p-benzoquinonechlorimine solution. To determine the antioxidant, the zone at Rf = 0.44 (located by means of iodine vapour) was removed and treated with fuming nitric acid sulfuric acid (1 1). The nitro-derivative of the antioxidant was determined in the product by polarography after the addition of urea and sodium acetate [35],... 

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