Volatile organic compounds 286 INDEX

The distillate may contain volatile neutral compounds as well as volatile acids and phenols. Add a slight excess of 10-20 per cent sodium hydroxide solution to this distillate and distil until it is judged that all volatile organic compounds have passed over into the distillate. If necessary, the determination of the refractive index of the distillate or the application of specific chemical tests (e.g. for carbonyl compounds use the 2,4-dinitrophenylhydrazine reagent) should be used to confirm completion of distillation. Keep this distillate (S,) for Step 4. 

Uehori and co-workers (1987) developed a retention index in GC to screen and quantify volatile organic compounds in blood. A dynamic headspace analyzer and GC/FID with retention indices were employed for the detection of 1,1-dichloroethane at nanogram levels. Uehori and co-workers noted that this method is simple, reliable and requires little or no sample preparation. 

In the 1970s, the EPA assumed a leading role in pollution control. With the realization that practically all solvents exhibited some level of photochemical activity, new rules—state and national—were focused on the total solvent content of paints as applied. The index used—VOC (volatile organic compound)—did not differentiate between solvents or coalescents but merely set limits in pounds of emissions per gallon of paint (excluding water) for varying industrial applications. 

Plasticizers for PVC are generally low-molecular volatile and flammable organic compounds. Their proportion in a highly plasticized PVC may reach 100 phr. in terms of the polymer. Plasticized PVCs, therefore, can be ignited in open air and they then burn freely. Their oxygen index may be as low as 20 per cent. 

The most common method used to determine the oxidative stability of fatty compounds is Rancimat (EN14214) also called OSl (Oxidation Stability Index). This test method consists in bubbling air through a sample maintained at llO C. This air is then passed through deionized water while the conductivity is measured. The sudden increase in water conductivity is due to soluble secondary oxidation products (volatile organic acids). The time at which the conductivity drastically increases is the induction time. 

Volatile oils (essential oils) are very complex, pleasant smelling, volatile mixtures containing many different compounds. Most of the essential oils have a high refractive index and they are often optically active. These properties are used for their identification and quality control. Essential oils have low water solubility but are readily soluble in organic solvents. Chemically and biosynthetically they are a heterogenous group. 

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