Normally volatile compounds in a non-volatile matrix are analyzed by Head Space technique. The bacterial culture sample (in liquid form?) will be definitely a sample with non-volatile matrix and hence cannot be introduced into a GC Capillary column. You can attach a Head Space Sampler on your GCMS and then the volatiles in your bacterial culture samples can be easily detected and quantified. You need to optimize the equilibration temperature and time for the analysis. This technique is quite sensitive and it will also avoid column and injector contamination.

I agree with Dr. Menon. I am attaching a paper on curry leaf essential oil on the use of head space technique with the premise it will be useful to you.

If possible, you can trap the gases on commercially available adsorbants or into solvents and analyse the contents.

Good luck

Passive samplers for VOC in liquids are not that common as in air. Anyhow you can use passive diffusion bag technique (low density poethylene bag filled with water) - you have to analyse the water inside the bad with some head space technique. Unfortunately you have to  adapt it for you purposes (make it smaller) - it was developed for undergound water sampling (http://www.itrcweb.org/Documents/PDBFAQs2.pdf). Basic question is how long you want to collect VOCs? If it is just a short time period you can use SPME (solid phase microextraction) - it is developed as fiber in syringe which is aplicable for GC/MS injection. You should apply it in head space (air above your cultures) in media it will be saturated in a while.

If you are interested in VOCs leaving your media you can use classis air VOCs sampler - active carbone. The desorption is simple - few minutes ultrasound extraction in carbon disulfide. Then you will inject CS2 solution. This is suitable method for volatile chlorinated compounds, BTEX, some esters and alcihols. Unfortunately it will be more-less qualitative analysis (showing composition of your products from culture media) as each compound has different diffucion rate to active carbon.

I have no experience with given GC/MS system so cannot help you more as I do not know autosampler construction etc.

Dear Dr. Malini,

Bacterial volatile organic compounds (VOCs) identified by Headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography–mass spectrometry (GC–MS) is recently used by some researchers. You need to a specific type of air tight closed culture flask with a septum and a tight screw cap to capture and prevent aganist evaporation of VOCs from your culture broth.VOCs were prepared by bacterial culture broth vial with a PTFE septum and a screw cap. Inoculated broths were incubated without shaking or shaking and subjected to volatile profiling via HS-SPME-GC–MS. SPME helps to concentrate and evaluated for extracting bacterial VOCs  for GC-MS analysis. GC–MS analysis, using electron impact ionization techniques and used both types of polar and non-polar column seperately. In addition, a blank sterile broth was also sampled via the HS-SPME method for compared your identification. Compounds such as pyrazines, dimethyl disulfide and phenylacetaldehyde have routinely been detected in blank broths and are thought to have been produced as a result of the autoclaving process. Pls see the following link for in details.

http://chromsci.oxfordjournals.org/content/52/4/363.long

Dear Dr. Malini, 

Most previous answers will give you get you well underway with your experiments. The most important consideration in the headspace sampling is choosing the (range of) molecules of interest for your question. There has been 

Article Volatile Metabolites of Pathogens: A Systematic Review

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So when you know what you're looking for you can choose your absorbent (take a look here: http://www.interscience.nl/images/pdf/sorbent%20poster.pdf ). I would not recommend using SPME as this method is based on reaching an equilibrium between the headspace and the fiber. This equilibrium is, for example, influenced by pH, which in turn may be influenced by the growth or type of the bacterium. 

Another important consideration is the culture material. I don't know what kind of application you want to find for VOC analysis. If that is a non-invasive and rapid detection of microbes you need to consider the substrates that you give the bacteria. The VOCs you find will be influenced by what the bacteria can consume and therefore you need to take your application into account. 

Good luck, Lieuwe