what is temperature programming in GS?
When is it used?
whats the advantage of it (comparing with isothermal seperation at low and high temperature)?

I would say you save yourself alot of time when u use it. For the rest it depends on what exact determination you are doing

You are doing a work on GC or something?

After injecting the sample onto the column the temperature of the column is raised from a lower temperature to a higher temperature. The temperatures and rate of increase vary depending on the sample mix and column but typically can range from a lower temperature of 40°C increasing to an upper one of 350°C at a rate between 3 to 15°C per minute.

Increasing the temp gives more energy to the molecules so they can escape from the stationary phase more easily into the mobile gas phase. So they spend less time in the stationary phase, so they move through the column faster.

This is a process where they are jumping in and out of the stationary phase and the more times they jump in and out the better the chance of separating two different types of molecule. If they dont go into the stationary phase they travel through unseparated. If go into the stationary phase but don't get out then obviously they won't separate because they they are stuck. What you need is a compromise.For a more basic explanation of terms see www.itsjustabox.com

It is used for separating samples containing analytes with a mixture of boiling points.

The advantages are time saving whilst still keeping the analytes separated

A low temperature alone will allow the lower bp analytes to separate but from the above the higher bp ones may take hours to move through the column. instead of half an hour. They get bogged down in the stationary phase

A high temperature alone will move the high bp ones through more quickly but I will leave you to think about what that would do to the low bp ones if they have so much energy that they spend hardly any time in the stationary phase.

Regards,

Ralph