The analysis in closed system for ensure the volatile organic compound from our interested samples only and avoid contamination from the environment. There are many sampling techniques such as passive sampling, active sampling and dynamic headspace. For passive sampling in chamber (closed system) for hypothetical situation by put the sample in the close system such as Teflon chamber, acrylic chamber. The stimulation may heat if the sample put in the heat condition after that put the adsorbent tube in the chamber. The sampling time of passive sampling technique should suitable with the amount of volatile compound more enough for analysis. Refer the standard method of US EPA (The United States Environmental Protection Agency) Passive Samplers for Investigation of Air Quality: Method Description, Implementation, and Comparison to Alternative Sampling Methods.
The active sampling technique was commonly used for environmental analysis and Pharmaceutical analysis. Example samples were essential oil, Hazard drug, electronic parts. This technique was same with passive sampling but the sampling method by sampling pump for suction the air into the adsorbent tube. This technique used the shorter time than passive technique, sometime the analysis method may increase factor for worst case such as the higher temperature, longer period. The reference methods were NIOSH  A vapor containment performance protocol of close system transfer devices used during pharmacy compounding and administration of hazard drug, NIOSH . Request for information on development of a performance test protocol for closed system transfer devices that incorporate air-cleaning technology to provide worker protection during pharmacy compounding and administration of hazard drug, HSE. Health and Safety Executive MDHS104 Volatile organic compounds in air, A NIOSH technical report of Guidelines for Air Sampling and Analytical Method Development and Evaluation.
Dynamic headspace sampling technique by purge the inert gas (Nitrogen gas) into the chamber for accelerate the volatile gas from sample. This technique will get more the volatile compound when compare the other. The reference methods were IDEMA M11-10, EN ISO 16000-9:2006 Determination of the emission of volatile organic compounds from building product and furnishing- Emission test chamber method.
After sampling vary technique continue analysed by Thermal desorption unit (TDU) with GC/MS (Gas Chromatography with Mass spectrophotometer). Data analysis by qualification and semiquantitative techniques. For qualification, ALS analysed all volatile organic compounds and compare the type of compound with GC/MS database (Nist/Wiley). For semi-quantitative technique, calculate the amount of compound by using only represent standard to compare amount all compounds.
ALS Pathumthani had experience for volatile organic compounds or outgassing analysis more than 15 years. the samples were easy volatile like perfume, essential oil, solvent reagent and hazard drug. The samples were semi-volatile like electronic parts, automotive part, paint and accelerate volatile by heating. ALS also designed the experiment for matching with the client’s sample