Phenacyl esters of fatty acids have been formed In an essentially quantitative manner using crown ethers as catalysts. These esters absorb UV radiation strongly at 254 nm, allowing the detection of as small a quantity as 1 ng of C2 acid, and 50 ng of C20 acid. The method of synthesis is inexpensive and can be carried out in virtually any aprotic solvent system in a short period of time. Reaction conditions do not require total exclusion of water, thus simplifying the procedure. Liquid chromatographic separations of these esters have been obtained on a 25-cm long column packed with Cg bonded phase. The implications and uses of such a broad ranging synthesis are discussed.Several reasons can be given for the use of derivatization in chromatography: e.g., to enhance solute volatility (GC), to enhance separation, and to enhance detectability. The selection of a derivative can often become much more difficult than the actual derivatization itself. In all areas of

The chromatographic broadening method of measuring diffusion coefficients, which until recently was used with gaseous mixtures, is shown to be useful for liquid mixtures. In this method, a small amount of solute (component 1) is injected into a flowing stream of a solvent (component 2). From the width of the eluted peak, the diffusion coefficient is measured. The constraints due to the liquid system, as well as possible sources of errors, are discussed. It is shown that with a well-designed injection port, a small-volume detector cell, narrow tubing, and low flow rate, good diffusion data can be easily obtained. Since the method is a dynamic one, the accumulation of the data is rapid, especially if a multiple-injection technique is used. The method was utilized to measure the diffusion coefficients of several alkylbenzenes in chloroform. It was found that as the side chain of the molecule lengthens, the diffusion decreases. The effect of molecular geometry was also investigated by observing the diffusion coefficients of structural isomers. The results seem to indicate that the more branched the molecule is, the faster the diffusion. The ramifications of these findings are discussed.

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The retention behavior on alkyl bonded stationary phases for liquid chromatography has been studied as a function of chain length, surface coverage, solute type, mobile phase composition, and temperature. The data indicate that depending on the degree of surface coverage and the type of solute, mixed mechanisms may play an important part in the retention behavior. Efficiencies and capacity ratios show an Increase as the bonded phase loading increases while asymmetry shows a decrease. Using a nonpolar mobile phase AH shows an odd-even effect as a function of the carbon number of the alkyl side chain in phenones. In a polar mobile phase AH seems to determine retention order except for the case of a heavily loaded column. In general, the data Indicate that alkyl bonded phase columns are most useful when the amount of bonded stationary phase Is maximized.(Jnabated interest has continued in the development of permanently bonded stationary phases for liquid chromatography. Though many such bonded phases continue to be prepared and applied to a great variety of separation problems with a high degree of success, few studies have been directed at providing a mechanistic description of their operation. Recent reviews (1-3) have aptly covered the current uses of bonded stationary phases in liquid chromatography. In a previous paper we have presented a detailed study on a polar bonded phase prepared by reacting Corasil II with 1-trimethoxysilylchloromethylphenylethane (4). Novotny and his co-workers (5) started with a similar material, but proceeded to hydrolyze the terminal chlorine to a hydroxyl group before studying its properties. Knox and Vasvari's (6) work on polymeric bonded phases presents one of the first systematic approaches of studying retention mechanism in bonded phases.Although much remains to be learned about the behavior of bonded phase systems, useful information has already been determined. Kirkland (7) has found that with polymeric phases adsorption on the polymer and interaction with stagnant pockets of mobile phases are important in determining chromatographic parameters. Little and his co-workers (8) have shown that in brush systems residual silanol groups play an important part in the separations. There are reasons to believe that this also holds true for liquid chromatographic systems.Karger and Sibley (9) have shown that in gas chromatography, when employing a nonpolar bonded brush system, the type of bonded phase determines the retention characteristics of the system. A recent study by Majors and Hopper (10) suggests that in reverse phase systems the retention increases as the length of the bonded phase increases. They did not find, however, a correlation between surface coverage and retention time. Locke (11) has demonstrated that the retention order, in reverse phase chromatography, is a function of the solutes solubilities in the mobile phase. In a study of in situ bonded stationary phases, Gilpin and his co-workers (12) have shown that increasing the length of the bonded phase from ethyl to oct...

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