Soils, non-polar

Studies of diffusional phenomena have direct relevance to detergency processes. Experiments are reported which investigate the effects of changes in temperature on the dynamic phenomena, which occur when aqueous solutions of pure non-ionic surfactants contact hydrocarbons such as tetradecane and hexadecane. These oils can be considered to be models of non-polar soils such as lubricating oils. The dynamic contacting phenomena, at least immediately after contact, are representative of those which occur when a cleaner solution contacts an oily soil on a polymer surface. With Ci2E5 as non-ionic surfactant at a concentration of 1 wt.% in water, quite different phenomena were observed below, above, and well above the cloud point when tetradecane or hexadecane was carefully layered on top of the aqueous solution. Below the cloud point temperature of 31°C very slow solubilisation of oil into the one-phase micellar solution occurred. At 35°C, which is just... 

This method can also be used to analyse soil samples. For instance, fenpropi-morph, which is a non-polar pesticide with good UV sensitivity but poor selectivity, has, after treatment, been determined in soil samples (31). In this example, an amount of soil was extracted overnight with acetonitrile this was then poured into a Buchner filter and rinsed with the same solvent. The acetonitrile solution was concentrated and, prior to LC analysis, the extract was diluted with water and 100 p.1 were then injected into the LC system. 

You have the task of purchasing some n-hexane for use in three different applications (i) pesticide analysis by gas chromatography, (ii) as a solvent to extract some non-polar high-boiling (200-300°C) oils from a soil sample, and (iii) as a mobile phase for HPLC analysis with UV detection. List and contrast the performance characteristics you need to take into account for purchasing the appropriate grade of hexane in each case. n-Hexane boils at about 70°C. Will any of your choices of hexane be suitable for use for HPLC analysis with fluorescence detection Explain your decision. 

By comparing the two adsorbents, it turns out that the non-polar character of the petroleum ether is exploited in the extraction from the strong nonspecific active sites of carbon black. On the other hand, the polar character of acetone makes the extraction from the highly strong specific active sites of the siliceous material of the soil possible. The retention time obtained with the mixture is intermediate between those two separate solvents, and the recovery, in turn, is higher. The proper choice of the solvent mixture plays a very important role on the size of the final volume of solution in which the pesticides are collected. 

Soil solubilization capacity, S Soil polarity In general, S is higher for polar soils than for non-polar ones... 

Table 4.6 gives a few representative values for Kow and Kp for non-polar organic substances on typical soil material and Table 4.7 gives estimates on typical retardation factors estimated for an aquifer. The data show that many non-polar organic substances, with the possible exception of very lipophilic substances such as hexachlorobenzene, are not markedly retarded in aquifers that contain little organic material (foe = 0.001 - 0.005). On the other hand, such substances are effectively retained in soils rich in organic carbon. 

Soxhlet extraction is commonly used for the extraction of non-polar and semi-polar trace organics from a wide variety of solid phases (i.e., sediments, soils, etc.) [192, 366, 380, 400-404]. The size of the systems can vary, but the more common configurations use between 100 ml and 200 ml of solvent to extract 20-200 g of sample. Larger systems can be used, but require proportionally more solvent. It is essential to match the solvent polarity to the solute solubility and to wet the matrix thoroughly with the solvent when extraction commences. 

Hassett 11, Banwart WL (1989) The sorption of non polar organics by soil and sediments. In Sawhney BL, Brown K (eds) Reactions and movement of organic chemicals in soils Soil Sci Soc Amer Spec Pub 22, Madison, pp 31-45... 

Modifiers were selected for addition to the spiked soil samples representing a range of solvent polarities. Based on the results of the density stepping experiments, the extraction times were increased to 19 minutes from 9.4 minutes, which increased the thimble volumes from 5 to 10. To be consistent throughout the experiments, 1 ml of modifier was added directly to each extraction cell. Methylene chloride was chosen as a non-polar modifier. Results show that the methylene chloride did little to aid in the extraction process for any herbicide. 

Due to their lipophilic nature, PCBs tend to accumulate or reside in those environmental compartments that are non-polar and are amenable to lipid accumulation, such as the organic components of sediments. PCB presence in polar substances, such as water, is minimal. PCBs are not volatile and thus do not persist in air in any appreciable concentration. Therefore, the major sources of environment exposure to environmental species remain soils and sediments. 

Despite its imperfections, the Koc approach is currently the most widely used and generally applicable method for predicting the sorption of organic compounds to soils and sediments. It is most appropriate for predicting the sorption of non-polar organic compounds... 

Surfactant molecules try to cover non-polar surfaces and displace oil and many other soiling components (Figure 4-6). An understanding of mechanisms may give ideas for product improvements. One might like to know the adsorption properties of the system to quantify its behaviour. 

Samples used to demonstrate this method were soil fulvic acid (SFA) and water fulvic acid (WFA), both well-characterized materials obtained from Dr. James H. Weber at the University of New Hampshire (19). Figure 1 shows that the chromatographic method resulted in four fractions separated for the SFA. The use of IP-RP-HPLC with the biological buffer MES resulted in sufficient separation to eliminate the need for gradients as have been used in previous studies (13-17). Simultaneous collection of UV (254 nm) and fluorescence (A citation = 332 nm and Remission = 42 nm) data showed similar chromatograms with peaks at the same retention times except in the case of the more non-polar (later-eluting) fractions which did not exhibit measurable fluorescence. This result is similar to that reported by Lombardi et al. (75) for marine DOM. Figure 2 shows a very similar separation for WFA. 

Lead, like mercury, causes neurological diseases. The organolead compounds are more toxic than mineral lead salts, since they are non-polar, lipid-soluble, and more readily cross the blood-brain barrier. This disease is related to mental retardation is children, lower performance on I.Q. tests, and hyperactivity. Severe exposure in adults causes irritability, sleeplessness, and irrational behavior. Some have gone as far as to blame anti-social behavior and criminality on sub-clinical Pb poisoning. A correlation between Pb in blood and Pb in air, dust and soils has been observed in many studies. The U.S. Centers for Disease Control has proclaimed a goal of reducing blood lead contents in children below 10 jag/lOOmL. 

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