I want to know the optimum auxiliary and carrier gas pressure, incubation time for the GC analysis of aldehydes and ketones (C-6 to C-9). I am not getting response even for methanol using HSS otherwise the system is fine and operating manually.
Perhaps your question relates with headspace analysis in DANI Gas Chromatograph. Does DANI Headspace have transfer line facility? or supplied with COMBIPAL system?
If system is working fine, then there may be issues with transfer line capillary (broken capillary),
or other end of capillary may not be installed properly (appropriate length missing) inside injector port. You also need to check the split ratio if S/SL injector is installed.
To overcome this, you may check the HS loop carrier pressure by setting a value like 20 psi or more. If there is leak, the setpoint shall difficult to achieve.
About 1 ml/min carrier gas flow will be enough in a 30 m x 0.25 mm id capillary column. As far as incubation time matters, solvent usually evaporates faster and requires less time but again method needs to be crosschecked in HS-GC system.
If you want to get grip on HS there is one book witch is unavoidable:
Static Headspace-Gas Chromatography: Theory and Practice, 2nd Edition
Bruno Kolb, Leslie S. Ettre
ISBN: 978-0-471-74944-8
It cover's the different implementations and also optimization strategies.
For all HS installations it is important dat you have a reference standard and application on witch you can fall back in case of doubt, something like 0.4% ethanol in water, 20min at 60°C, suitable settings can be found in the european pharmacopeia, 2.4.24. Identification and control of residual solvents, get used to check for repeatability and linearity on a regular basis
About Dani I use to have their old device witch are similar to the 86.50. This device has a heated sample loop and and a heated transferline . There are several way's to get the plumbing done so you need an actual schema depicting your installation in order to understand what's going on, HS is a marvelous technique but it is rather physical, a mental image helps a lot. In the most simple version it is the headspace who supplies the carrier to the gc, a split is needed in order to have a sufficiently high flow in the transfer line The carrier gas pressure can be calculated by adding the pressure needed on the column head to the pressure drop over the transferline witch will a result of the splitflow+ carrierflow through this one. Agilent has a nice free program on its site to calculate those things
http://www.chem.agilent.com/en-US/Technical-Support/Instruments-Systems/Gas-Chromatography/utilities/Pages/GCCalculators.aspx
As far as I remember (I switched to perkin elmer) the auxiliary pressure -in the simple instalation- is used to pressurize the vial in order to provide the driving force to fill the sample loop. If it is to low then the vial pressure will be released during the pressurization step, to high means a dilution of the sample. By applying the universal gas low and the vapor pressure of the matrix you can calculate the equilibrium pressure in the vial, don't forget to compensate for the air expantion due to the temperature rise. In order to have repeatable results the applied pressure should be higher then the calculated one.
One of the problems I had with this implementation is ' a sticking valve'' . There is a valve controlling the time the sample loop is filled against the atmospheric pressure . If this valve sticks ( for instance due to Xylene samples) the loop remains empty and there will be no signal. To check if the valve is still functioning, locate the exit tube where the pressure from the vial is released trough the sample loop to the atmosphere, connect a small tube and put the other end into liquid, during loopfilling there should be bubbles.