There is a constant drive to speed up GC separations. Shorter analysis times provide more analyses per day, which reduces cost. One approach is to reduce column length and column diameter and columns ...of 0.15 mm i.d. have indeed grown in popularity. However, the majority of applications are still done with 0.25 mm and 0.32 mm columns.
Two different injectors, a split/splitless injector and a programmed temperature vaporizer (PTV) injector were investigated as the interface in on-line supercritical fluid extraction (SFE)-capillary ...gas chromatography (cGC). The parameters affecting the chromatographic peak shapes as well as the quantitative performance of the interfaces in on-line SFE-cGC were identified and studied. Particular attention was paid to the case where modified extraction fluids were used. Experiments were performed on two different samples. The first sample consisted of PAHs spiked on sand at different concentration levels. The other sample was a polymeric material.
The effects of modifier addition and temperature variation on the supercritical fluid extraction of nylon-6 and poly(1,4-butylene terephthalate) samples are discussed. The modifiers studied include ...hexane, chloroform, methanol, and benzene. The influence of experimental parameters, such as extraction temperature and pressure, static time, and supercritical fluid flow rate, are investigated systematically with both pure and modified carbon dioxide. The addition of a suitable modifier results in significantly enhanced extraction rates, particularly at low extraction temperatures. A simple experimental setup for the introduction of additional volumes of modifier during the extraction was developed and evaluated. Guidelines for the optimization of the supercritical fluid extraction of polymeric samples are given.
The high-frequency and high-speed printed circuit board (PCB) with lower transmission loss, higher heat resistance, and better processability play increasing significant roles in mobile communication ...technology. However, because the materials and micro drilling process of high-frequency and high-speed PCB are very different from the traditional printed board, there are still many of key techniques to be explored in the future study. In this paper, the characteristics of high-frequency and high-speed PCB were presented. Researches concerning the design and wear ability of micro drill, the analysis of micro drilling force and temperature, and the quality of micro holes were reviewed. Finally, several key techniques and challenges regarding materials and micro drilling were suggested.
PDF
