Gas-liquid chromatography of silylated glycols and terephthalate esters

Experimentally measured mass absorption coefficients in quantitative x-ray diffraction analysis

“…This separation method, like any other, requires a sensitive and versatile detector to be used most effectively. Detection methods based upon the absorption or emission of radiant energy have been most popular in the recent past (2). While both single and variable wavelength detectors are available, most commercial instruments have utilized single wavelength or manually operated variable wavelength systems.…”

“…The mass absorption coefficient was determined from (2): log Ic = k-k¡ log µ (2) where k = 5.232386, kt = 1.6651904 with = 1.50 A (approximately the wavelength radiation of Cu Ka), The Compton radiation intensities for the analyzed samples are reported in Table IV together with the mass absorption coefficients determined in the literature and obtained from the relation (2). A standard deviation of about ±3.4% between the experimental and theoretical values of µ was computed.…”

Supercritical fluid extraction and chromatography for the determination of oligomers in poly(ethylene terephthalate) films

“…[In (8/ir2) -te/tc + In (1 + (2/9) exp(-ta/tc)|]N (17) A plot of In [(m/m0y against the number of extractions, N, should therefore give a straight line with an intercept of -In [1 + (2/9) exp(-tr/tc)}. Experience with continuous extraction indicates that the intercept may be different from this value for various reasons.…”

“…The effect of retinoids in the prevention of cancer has also been studied (13,14). Since cis and trans isomers of a given retinoid may not have the same biological activities (15)(16)(17) and because these compounds can undergo photochemically induced double-bond isomerization (18), an analytical technique ca-pable of separating such isomers is necessary. Additionally, it is desirable for this technique to be sensitive enough to analyze small quantities of material, especially for synthetically derived retinoid analogues.…”

“…The cyclic trimer (ET)3 has been found to make up the majority of these oligomers and was first separated and identified from PET film by Ross et al in 1954 (2). Since then a wide variety of chromatographic methods have been used to identify and analyze the oligomers, including paper chromatography (3), liquid column chromatography (4), thin-layer chromatography (5)(6)(7)(8)(9), gel-permeation chromatography (10)(11)(12)(13)(14), gas chromatography (GC) for the very low oligomers (15) or after derivatization (16,17), and HPLC (18)(19)(20)(21)(22), which is now the preferred method. The extraction method generally used prior to analysis has been a Soxhlet extraction (up to 24 h) using chloroform, 1,4-dioxanes, toluene, or xylenes. Cooper and Semiyen (12) precipitated the high polymers from a solution of PET in 1-methylnaphthalene, leaving the lower oligomers behind in solution.…”