主题：【求助】为什么六通阀切换后会出现一较大倒峰？？

可能是水峰

原文由 louis315 发表:
可能是水峰

可是以前正常啊，基本不波动，再说了，水峰也应该是一正峰。谢谢你的讨论

原文由 guoyan0725 发表:
本人使用一台色谱，FID，带一自动六通阀，空气驱动，与FID共用一空气发生器，可是每次进样后，阀切换后就会出现一负峰，大约走一分钟左右，然后平稳，以前是好的，不知道是什么原因引起的，各个连接点我也查了，没有漏气的地方，请帮帮忙，谢谢！

是不是在切换过程有其他物质进入产生了峰啊？
为什么要接六通阀啊？是做什么的啊？没见过！

矿井气中的CO,CH4,CO2,C2H2等。
进空气也是这样的，可是空运行的时候，负峰就是小得多了，基本正常了。不知道为什么？

可能是六通阀有内漏。

气动阀动作用气造成的空气压力波动吧。

是不是空气压缩机老化供气不足啊，或者缓冲罐没了？不行安装一个空气缓冲罐试试看。

应该是你用的稳流阀，进样后六通阀内定量管压力低于载气压力，导致载气压力下降引起的反峰，
你可以加个背压阀调节六通阀内定量管压力与载气压力一致

原文由 louis315 发表:
可能是水峰

fid对水峰不响应吧！？？

原文由 hzhhqt 发表:
应该是你用的稳流阀，进样后六通阀内定量管压力低于载气压力，导致载气压力下降引起的反峰，
你可以加个背压阀调节六通阀内定量管压力与载气压力一致

学习了。
PS：此寒江雪亦彼寒江雪？

As is the case with all detectors for gas chromatography, thermal control of
a FID is an important requirement. The block enclosing the detector should be
heated above the temperature of the column to avoid the condensation of sample
components in the transfer lines and jet. In addition, the temperature must be
above 100 oC to prevent water condensation. Since the temperature of the body
of the detector has a slight effect on the detection mechanism it must be stable.
However, it is more important to keep the detector from getting too hot since
solid surfaces heated by the flame can emit electrons (i.e., thermionic ionization).
For example, a large sample or component that can increase the temperature can
cause a positive detector response, including samples or components that otherwise
would have given a negligible response (e.g., CO). Under such conditions,
water may give a negative peak, as it decreases the temperature of the flame.Overheating the detector can also lead to electrical leakage across insulators,
causing instability in the detector output current.
《Modern Practice of Gas Chromatography》