Static Headspace Analysis

Static headspace analysis (SHA) is a gas-chromatography (GC) technique utilized to analyze complex samples that contain volatile components.  This type of analysis is utilized to determine the volatile organic content (VOC’s) in pharmaceutical products, ethanol content in blood samples, contaminants in soil samples and monomer concentrations in polymer products, just to name a few.  Briefly summarized, analysis involves the introduction of a sample (liquid, solid or viscous in-between) into a headspace vial.  The headspace vial is sealed and the volatile components of the sample are allowed to equilibrate with the gaseous headspace.  This equilibration step often involves heating or sample agitation.  Once the volatile components of the sample arrive at equilibrium in the headspace, that headspace is sampled and sent through the GC for analysis.  The seal between the vial and their lids are critical for accurate, reliable and reproducible analyses.  Once the sample has been sealed in the vial, it is often heated (creating higher internal pressure) or agitated to facilitate establishing equilibrium between the sample and the headspace.  If agitating the sample or heating creates an internal pressure that ruptures the seal of headspace vial, it completely compromises the integrity of the sample itself.

Static Headspace Analysis

While there are many benefits for utilizing headspace gas chromatography as an analytical technique, the two obvious ones are time and money.  For samples that contain myriad analytes, this technique saves a tremendous amount of time and money often spent in multiple separation/isolation steps.  SHA allows a sample containing a volatile analyte to be sampled directly instead of undergoing several costly and time consuming steps to remove the analyte from the original sample.  This direct sampling saves companies a tremendous amount of time which improves turnaround time as well as (possibly) customer satisfaction.  Furthermore, it reduces the amount of organic solvents companies would need for these separation/isolation steps, thereby reducing operational and disposal costs.  For pharmaceutical companies, this technique gives peace of mind in their QA/QC departments as they analyze for VOC’s in a way that doesn’t destroy their potentially valuable samples.

Perhaps the greatest benefit of static headspace analysis comes from the nature of the sample injected.  It’s initially in the gas phase.  When sampling a complex mixture that contains multiple high molecular weight analytes, these substances often require extreme conditions for complete analysis.  GC, and GC-MS rely on samples in the gas phase, oftentimes requiring elevated temperature conditions to convince recalcitrant compounds to become volatile. One of the problems with those analyses stems from the residual material often left behind on the column after the run.  These residual artifacts can, and often do, surface on subsequent GC runs and render these trials as useless.  However, static headspace analysis alleviates that concern by only analyzing samples that are already in the gas phase.  This analysis method saves a tremendous amount of time and money in the form of capillary column purchase savings (columns often last for years), reduced downtime for purging columns contaminated with residual high molecular weight materials and reduced GC maintenance time.