Some compounds have high boiling points as well as being air sensitive. A simple vacuum distillation system as exemplified above can be used, whereby the vacuum is replaced with an inert gas after the distillation is complete. However, this is a less satisfactory system if one desires to collect fractions under a reduced pressure. To do this a "pig" adaptor can be added to the end of the condenser, or for better results or for very air sensitive compounds a Perkin triangle apparatus can be used.

The Perkin triangle, has means via a series of glass or Teflon taps to allows fractions to be isolated from the rest of the still, without the main body of the distillation being removed from either the vacuum or heat source, and thus can remain in a state of reflux. To do this, the sample is first isolated from the vacuum by means of the taps, the vacuum over the sample is then replaced with an inert gas (such as nitrogen or argon) and can then be stoppered and removed. A fresh collection vessel can then be added to the system, evacuated and linked back into the distillation system via the taps to collect a second fraction, and so on, until all fractions have been collected.

有些化合物不但沸点高，而且对空气敏感。因而。可使用简单真空蒸馏系统（如上所举的例子），蒸馏完成之后，用惰性气体填充真空。可是，如果想在负压下收集馏分这套系统就不能令人满意。为了在负压下收集馏分，可在冷凝器末端加装一个pig 转接器，或者可采用Perkin triangle设备，以取得较好的结果或用于空气极敏感化合物的蒸馏。

The Perkin triangle　通过一系列的玻璃或特氟纶阀门使馏分与剩下的蒸馏物隔离，而不用将蒸馏主体与真空或热源分开，这样可保持回流状态。为了做到这点，首选将样品与真空用阀门隔开，然后将样品上面的真空用隋性气体代替（如氮气或氩气），然后塞上塞子移走。这时可将新的收集容器连接到系统上，再通过阀门退下来后再次连接到蒸馏系统内以收集二次馏分。就这样直至收集完全部馏分。