Bases fraction

The almost dry residue is cooled to 0°C and made strongly alkaline with a 50% potassium hydroxide solution. The amine is extracted into several portions of ether, dried over potassium hydroxide, the solvent removed, and the base fractioned. Reaction of the base with a half-molar quantity of sulfuric acid gives the sulfate. 

The purpose of the main fractionator, or main column (Figure 1 -1 o i, is to desuperheat and recover liquid products from the reactor vapors. The hot product vapors from the reactor flow into the main fractionator near the base. Fractionation is accomplished by condensing and revaporizing hydrocarbon components as the vapor flows upward through trays in the tower. 

N— compounds used as acid inhibitors include heterocyclic bases, such as pyridine, quinoline and various amines. Carassiti describes the inhibitive action of decylamine and quinoline, as well as phenylthiourea and dibenzyl-sulphoxides for the protection of stainless steels in hydrochloric acid pickling. Hudson e/a/. refer to coal tar base fractions for inhibition in sulphuric and hydrochloric acid solutions. Good results are reported with 0-25 vol. Vo of distilled quinoline bases with addition of 0 05m sodium chloride in 4n sulphuric acid at 93°C. The sodium chloride is acting synergistically, e.g. 0-05m NaCl raises the percentage inhibition given by 0-1% quinoline in 2n H2SO4 from 43 to 79%. Similarly, potassium iodide improves the action of phenylthiourea . 

Isolation of Antimicrobial Alkaloids from Tertiary Non-phenolic Base Fraction - A 2 g portion of the crude nonphenolic base fraction was dissolved in chloroform and chromatographed over 200 g of aluminum oxide (Woelm, neutral, grade III). The solvents used were 300 ml of chloroform, 500 ml of 1Z methanol in chloroform, 300 ml of 2Z metha-... 

Table I - Chromatographic Separation of Tertiary Nonphenolic Base Fraction...

Kosian, P.A., E.A. Makynen, P.D. Monson, D.R. Mount, A. Spacie, O.G. Mekenyan, and G.T. Ankley. 1998. Application of toxicity-based fractionation techniques and structure-activity relationship models for the identification of phototoxic polycyclic aromatic hydrocarbons in sediment pore water. Environ. Toxicol. Chem. 17 1021-1033. 

Mossbauer spectroscopy involves the measurement of minute frequency shifts in the resonant gamma-ray absorption cross-section of a target nucleus (most commonly Fe occasionally Sn, Au, and a few others) embedded in a solid material. Because Mossbauer spectroscopy directly probes the chemical properties of the target nucleus, it is ideally suited to studies of complex materials and Fe-poor solid solutions. Mossbauer studies are commonly used to infer properties like oxidation states and coordination number at the site occupied by the target atom (Flawthome 1988). Mossbauer-based fractionation models are based on an extension of Equations (4) and (5) (Bigeleisen and Mayer 1947), which relate a to either sums of squares of vibrational frequencies or a sum of force constants. In the Polyakov (1997)... 

Isco, Inc. The CombiFlash Sg 100c System is suitable for purifying 10 to 35 g of material. It provides time- or peak-based fraction collection with on-line UV detection, and a linear and/or step gradient with two solvents at a flow rate of 10 to 100 mL/min. 

Murray (4I) has recommended that, so far as film stability of larvicidal mixtures is concerned, the oil should have either a small or a very high aromatic content (it should not contain 50% of aromatics unless they are very high boiling—e.g., of lubricating base fraction) consist of a mixture of wide and overlapping cuts of oil and should not contain fats or fatty acids added as spread-aiders. If a spreading agent is desired, resins should be employed. 

In summary, equilibrium condensation represents one end member of a continuum of gas-solid interactions that took place in the early solar system. Some samples appear to have formed under conditions that closely match those of equilibrium condensation. But the volatility-based fractionations that are widely observed in solar system materials are due to much more complicated processes that involve evaporation (the opposite of condensation) or mixing of materials produced under different conditions, as well as a variety of processes in which kinetic effects played an important role. 

Seiber JN, Glotfelty DW, Lucas AD, et al. 1990. A multiresidue method by high performance liquid chromatography-based fractionation and gas chromatographic determination of trace levels of pesticides in air and water. Arch Environ Contam Toxicol 19 583-592. 

The liquid-liquid, acid-base fractionation method was preferred over HPLC by the liquid waste panel members because it is a better validated technique for the isolation of components that are toxic or that might otherwise interfere with the assay. Also, the distribution of activity in the acid, base, and neutral fractions provides a preliminary estimate of the types of chemicals responsible for the mutagenicity. 

Hydrophobic Base Fraction. The hydrophobic base fraction was adjusted to pH 10. A 50-/uL aliquot of the aqueous solution was subjected to HPLC analysis to test for the presence of 5-chlorouracil. The remaining aqueous solution was solvent extracted with methylene chloride. The extract was first concentrated in a Kudema-Danish apparatus, then under a stream of N2, and analyzed by GC-FID and GC-MS. 

Hydrophilic Base Fraction. An aliquot (1-2 mL) of the hydrophilic base fraction was dried under a stream of N2, acidified with HC1, and analyzed for glycine after derivatization with isoamyl alcohol, acetyl chloride, and hep-tafluorobutyric anhydride according to the procedure described by Burleson et al. (23). An aliquot (1-2 mL) of the same hydrophilic base fraction was analyzed for quinaldic acid following the procedure mentioned for the hydrophobic acid fraction. The remaining portion of the hydrophilic base fraction was extracted at pH 10 with 50 mL of methylene chloride. The extract was concentrated to 1 mL and analyzed by GC-FID and GC-MS. 

Preliminary experiments resulted in the formation of a precipitate due to the presence of inorganic salts when the pH of the test solution was raised to 10 for the first passage through the XAD-8 column to isolate the hydrophobic base fraction. Initially, desalting the solution with a cation-exchange resin (i.e., AG-50-X8, Na+ form) was tried before... 

In consideration of the results presented in Tables II and III, it was decided to integrate the resins and carbon columns in a single scheme as shown in Figure 1. The test solution was adjusted to pH 7 immediately following the AG MP-50 column and processed through the Carbopack B column. The results from one experiment conducted under these conditions practically confirmed the overall process performance anticipated from the individual experiments (see Table IV). Trimesic acid, stearic acid, and humic acids were found in the hydrophobic acid fraction quinoline was primarily quantitated in the hydrophobic base fraction, whereas a small amount of it was also detected in the hydrophobic neutral fraction. Isophorone, biphenyl, 1-chlorododecane, 2,6-di-ter -butyl-4-methylphenol, 2,4 -dichlorobiphenyl, 2,2 5,5 -tetrachlorobiphenyl, anthraquinone, and phenanthrene were re-... 

Neutral Lewis bases were removed by contacting the acid- and base-free bitumen with ferric chloride/Attapulgus clay in a column system. Weakly adsorbed complexes were desorbed with 1,2-dichloroethane while strongly held complexes were desorbed with benzene and methanol. This procedure provided two neutral Lewis bases fractions for analysis. 

The three base fractions were titrated for basic nitrogen to determine the average strength of the bases and the amount of titratable nitrogen present. All titratable material was assumed to be nitrogen bases, although sulfoxides are present and may titrate as weak bases (18, 21). The results are given in Table VII. The first two base fractions contain... 

The nitrogen content in the base fractions increases with increasing polarity. If monofunctionality is assumed, this would indicate that the molecular weight decreases as the polarity increases. This is contrary to the VPO molecular weight data, which again indicates substantial... 

The acid, base, and neutral Lewis base fractions consist of polar molecules capable of hydrogen bonding and, therefore, of intermolecular association. These polar fractions, which constitute nearly two-thirds of the 675°C+ residuum, have high concentrations of heteroelements in comparison to the nonpolar aromatic and saturate hydrocarbons, as shown in Table IX for the residuum from a Russian crude oil. Infrared spectroscopy of the acid fraction revealed mostly pyrroles with phenols but only traces of... 

The tertiary base fractions of both Thalictrum longistylum D.C. and T. podocarpum Humb. contained iV-desmethylthalistyline (134), C40H46N2Og, amorphous, [a]D +151° (c 0.2, MeOH). Its structure was elucidated by conversion to the bis quaternary salt, thalistyline methodiiodide (Section II,C,60) (77, 78). 

Lukasewycz, M.T. and Durhan, E.J. (1992) Strategies for the identification of non-polar toxicants in aqueous environmental samples using toxicity-based fractionation and gas chromatography-mass spectrometry, Journal of Chromatography 580, 215-28. 

Base Fractions. The base contents of the 325° to 425° C distillates were quite low (range 0.03 to 0.88 wt-pct) but correlated well with the nitrogen contents of these distillates, as shown in Figure 6 (correlation coefficient 0.90). Similarly, the bases in the 425° to 540° C distillates were low (range 0.06 to 0.54 wt-pct) and correlated fairly well with the distillate nitrogen content (coefficient 0.79). 

The acid-free sample was quantitatively transferred to the cation-exchange resin (oa. 150 ml) wet-packed as described above. Unreactive materials were eluted under an argon atmosphere with pentane for oa, 48 hours at a rate of 6 to 10 drops per minute. The reactive materials were recovered by eluting the resin with benzene and then with an 8% 2-propylamine in methanol solution (V/V). The two eluents were combined to yield the total base fraction. 

It is interesting to note that the anthracene-oil-base fraction contains heterocyclic compound types containing two nitrogens (33). This appears to be the first report of numerous SjH2N+ZN2 comPounc s i-n coal liquids. Minor amounts of dinitrogen compounds have been previously observed in these materials (34). 

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