Complexed samples, doubly

Although much of the work referred to in this paper was done several years ago, it was not reported previously. The content and implications are sufficiently novel to merit mention even at this time. The fracture surface morphology of doubly oriented nylon 66 was studied in its untreated and I2-KI complexed state. All the work reported here was done on doubly oriented samples made from an unoriented nylon 66 rod according to the techniques outlined below. 

Mechanistic Studies. - The mechanism of the reaction of tetra-zole-activated phosphoramidites with alcohols has been studied. A series of diethyl azolyl phosphoramidites (85) was prepared from diethyl phosphorochloridite and fully characterized, and the same compounds shown to be formed from the phosphoramidite (86) and azole. The degree of formation of (85) from (86) increases with the acidity of the azole, and the proposed mechanism is a fast protonation of (86), followed by a slow, reversible formation of (85) and a fast reaction of (85) with alcohols. Another study was concerned with the influence of amine hydrochlorides on the rate of methanolysis of the phosphoramidites (87) or (88), or tris(diethylamino)phosphine.The chloride content was measured to be 10-20 mM in doubly distilled samples which explains that "uncatalysed alcoholysis is possible. Intensive purification, including treatment with butyllithium and distillation from sodium, brought the chloride content down to 0.1-1 mM. The methanolysis reaction, in methanol as the solvent, was found to be first-order in catalyst concentration. An aJb initio calculation on N- and P-protonated aminophosphine (89) gave similar proton affinities for N and P this contrasts with earlier MNDO calculations which had ff-protonated species as the most stable. The M-protonated compound had an electronic structure reminiscent of a phosphenium ion-ammonia complex. 

Howeva, if the sample consists of a mixture of two fluoro-phores, or a single fluotophore that diqrlays two decay times, dien die fluorescence decay is doubly exponential. Multiexponentiai decays are fieqnendy encountered in biochemical fluorescence, and still more complex decays are found fen colUsional quenching cn in the pretence of spectral relaxation. Phase angles and demodulation factors may still be measured, but these values, when interpreted according to Eqs. [22.1] and [22.2], yield only apparent, and not actual, lifetimes. 

The case of the very complex doubly disordered Ba, (Sn,(CI +yP solid solution, where Ba + and Sn + were found to be fully disordered on the Ba + site in the precipitated samples. Samples prepared in dry conditions at high temperatures are even more complex since they contain both Sn " " ions and covalently bonded Sn(ll) disordered with one another and with Ba " " ions, all on the same site, with the Sn " " ion being very loosely held in its site. 

The high ionization efficiency that characterizes plasma source mass spectrometers also has drawbacks, however. In particular, isotopic analysis by MC-ICP-MS is more susceptible than TIMS measurements to spectral interferences from isobars, molecular ions, and doubly charged species. Such interferences are furthermore much more problematic for isotope ratio than for element concentration measurements, as isotopic compositions typically need to be measured with an accuracy and precision of better than 100 ppm. In order to reduce spectral interferences to tolerable levels, isotopic analyses of complex natural samples in geo- and cosmochemistry are generally carried out following separation of the... 

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