Volume 77, Issue 4

Plasma-induced surface radicals formed on a variety of organic polymers have been studied by electron spin resonance (ESR), making it possible to provide a sound basis for future experimental design of polymer surface processing (i.e., plasma treatment). On the basis of the findings from such studies on the nature of radical formation and radical reactivity, several novel bioapplications in the field of biomedical and drug engineering have been developed. Applications derived from the nature of plasma-induced surface radical formation include the preparation of a reservoir-type drug delivery system (DDS) of sustained and delayed release, and a floating drug delivery system (FDDS) possessing gastric retention capabilities, the combined findings leading to preparation of a novel “patient-tailored DDS” administered under consideration of the fact that the environment (pH and transit time, etc.) in the gastrointestinal (GI) tract varies with each patient. Applications derived from the reactivity of plasma-induced surface radicals include the preparation of composite powders applicable to a matrix-type DDS by making a mechanical application to the surface radical-containing polymer powders with drug powders, plasma-assisted immobilization of oligo -nucleotides (DNA) onto polymer surfaces applicable to constructing a DNA diagnosis system, and basic study of plasma-assisted preparation of a novel functionalized chemo-embolic agent of non-crosslinked hydrogel, vinyl alcohol-sodium acrylate copolymer (PVA-PAANa).

An assessment of high-temperature mass spectrometry and of sources of inaccuracy is made. Experimental, calculated, and estimated cross-sections for ionization of atoms and inorganic molecules typically present in high-temperature vapors are summarized. Experimental cross-sections determined for some 56 atoms are generally close to theoretically calculated values, especially when excitation–autoionization is taken into account. Absolute or relative cross-sections for formation of parent ions were measured for ca. 100 molecules. These include homonuclear diatomic and polyatomic molecules, oxides, chalcogenides, halides, and hydroxides. Additivity of atomic cross-sections supplemented by empirical corrections provides fair estimates of molecular cross-sections. Causes of uncertainty are differences in interatomic distances and in shapes of potential energy curves (surfaces) of neutral molecules and of molecular ions and tendency toward dissociative ionization in certain types of molecules. Various mass spectrometric procedures are described that render the accuracy of measured thermodynamic properties of materials largely independent of ionization cross-sections. This accuracy is comparable with that of other techniques applicable under the conditions of interest, but often only the mass spectrometric procedure is appropriate at high temperatures.

This document presents a critical evaluation of the equilibrium constants and reaction enthalpies for the complex formation reactions between aqueous Hg(II) and the common environmental inorganic ligands Cl – , OH – , CO 3 2– , SO 4 2– , and PO 4 3– . The analysis used data from the IUPAC Stability Constants database, SC-Database , focusing particularly on values for 25 °C and perchlorate media. Specific ion interaction theory (SIT) was applied to reliable data available for the ionic strength range I c < 3.0 mol dm –3 . Recommended values of log 10 β p,q,r ° and the associated reaction enthalpies, ∆ r H m °, valid at I m = 0 mol kg –1 and 25 °C, were obtained by weighted linear regression using the SIT equations. Also reported are the equations and specific ion interaction coefficients required to calculate log 10 β p,q,r ° values at higher ionic strengths and other temperatures. A similar analysis is reported for the reactions of H + with CO 3 2– and PO 4 3– . Diagrams are presented to show the calculated distribution of Hg(II) amongst these inorganic ligands in model natural waters. Under typical environmental conditions, Hg(II) speciation is dominated by the formation of HgCl 2 (aq), Hg(OH)Cl(aq), and Hg(OH) 2 (aq).