If you're interested in using gas chromatography on the cheap, this project may be of interest. Before moving any further, gas chromatography is (according to Wikipedia):
... a common type of chromatography used in analytical chemistry for separating and analysing compounds that can be vaporized without decomposition. Typical uses of GC include testing the purity of a particular substance, or separating the different components of a mixture (the relative amounts of such components can also be determined). In some situations, GC may help in identifying a compound. Inpreparative chromatography, GC can be used to prepare pure compounds from a mixture.
Arduino forum member "Harristotle" has documented the build and sketch for his own version of a GC machine, which uses borosilicate glass pipe filled with silica gel to separate and identify halogenated alkanes. The pipe is inserted into a custom oven whose temperature is controlled via the Arduino.
It's an interesting device even if you don't have a use for it, or if you do - log in to the Arduino forum for details and discussion. And for more, we're on twitter and Google+, so follow us for news and product updates as well.
If you're making a similar project and need to control large currents with your Arduino digital outputs - you'll need a MOSFET. We've got you covered with out NDRIVE: N-MOSFET driver/output module:
This high-power N-MOSFET module lets you switch high-current loads using a tiny microcontroller. Perfect for controlling that set of traffic lights mounted in your living room! Works brilliantly for automotive projects such as switching high-power 12V lights and high wattage LEDs. For more information and to order, visit the product page.