瓦里安系列7瓦里安气相层析仪教材(繁体)(免费阅读).ppt

氣相層析儀基礎課程 講員 : 張 世 春 E-mail : kyle.chang@ 日期 : 1999 年 7 月 15 日 主辦 : 美商亞洲瓦里安科技(股)臺灣分公司 Column Materials and Construction Packed columns - Short (2-3 m), wide bore tubing. Capillary columns - long ( 60 m), narrow bore tubing. All materials should be thermally and chemically stable. Thermally stable - temperatures needed for analyses will not decompose the column materials. Chemically stable - Temperatures, free of analysis will not decompose the column materials. Use chromatography grade, clean materials. Packed Columns Stainless steel tubing is most often used because it is inert and rigid. Glass, nickel, and teflon-lined stainless steel are also available (more inert). Solid Support Serves as base for liquid phase. Increases surface area available to sample. Small, uniformly sized, porous particles. High concentration of silica. Standard mesh sizes. Silylation Surface deactivation. Washing with strong acid removes metals. Chemical treatment (DMCS, TMCS). Final polarity compatible with stationary phase. R—SiOH + (CH3)2SiCl2 ? R—SiOSi(CH3)2Cl R—SiOSi(CH3)2Cl + CH3OH ? R—SiOSi(CH3)2OCH3 Methyl functional groups replace alcohol groups. Liquid Phases (GLC) Uniformly coated on the solid support. Recommended loading 2% - 10% by weight. Non-volatile liquids. Selectivity-separating power. Vary in chemical composition. Solid Adsorbents (GSC) ? Porous adsorbents. ? Requires no liquid phase. ? Silica gel, alumina, molecular sieve. ? Porous polymer beads. - Ethylvinyl benzene cross-linked with divinyl benzene. - Functions as solid support and stationary phase. - Available in range of polarities. Capillary Columns Stainless steel ? glass ? fused silica. Flexible but mechanically strong. Inert. 0.05 - 0.80 mm ID. Lengths greater than 100 m possible, 30 m most common. Layer of polyimide applied to outside to fill flaws and strengthen. Inner surface undergoes silylation. Stationary phase coated on i