Adjusting the Temperature of the Chromatograph: The temperature of the column, the injection port, and the detector is an important consideration for any gas chromatography experiment. Typically, these parameters will be set by the instructor, but you may be required to optimize the separation conditions. The column temperature is usually determined experimentally - the experimental parameters, including temperature and flow rate (see below), are adjusted until an acceptable separation is observed. An increased column temperature generally results in shorter retention times and narrower peaks, but at the expense of decreased resolution of the peaks. Most columns cannot withstand temperatures greater than 250-350 °C, so the temperature should never be allowed to exceed 200 °C unless an instructor specifically directs that a higher temperature be used. The injection port temperature and the detector are usually set about 25 degrees above the temperature of the column. Always record all of the temperature settings from the gas chromatograph for each sample.
Video. Adjusting the rate of gas flow.
Adjusting the rate of gas flow: Connect the tubing from the bubbler to the appropriate gas outlet on the chromatograph. Squeeze the bulb on the bubbler until an air bubble begins to rise through the bubbler tube, and monitor the rate at which the bubble rises to the top of the tube. If necessary, use the appropriate gas flow adjustment knob to change the gas flow rate to that specified for your instrument. A higher gas flow will result in shorter retention times and poorer peak resolution
Recording the Data: Data collected from a gas chromatogram can be collected with a computer or a chart recorder (see the Chart Recorder module for more information). Familiarize yourself with the equipment available to you before beginning any experiment.
