Multiple Headspace Extraction Research Articles

Determination of residual solvents in a transdermal system by means of headspace gas chromatography

Pharmaceutical products have to be tested for impurities including residual solvents. This is also required in production control. The simplest solution to this problem is headspace gas chromatography. This paper describes the determination of residual volatile hydrocarbons in the transdermal system DEPONIT by only one headspace measurement. Accuracy is ensured by the multiple headspace extraction technique.

Quantitative headspace analysis of solid samples; a classification of various sample types

Volatile compounds in various solid samples have been analyzed quantitatively by equilibrium headspace gas chromatography with the technique of multiple headspace extraction (MHE). Solid samples can represent either a partition system, such as certain polymers, or an adsorption system, particularly when present as porous material. It has been found that the humidity of the sample has a strong influence on the equilibration in an adsorption system with a hydrophilic matrix and that the addition of water increases the volatility and speeds up the equilibration time. The influence of various important parameters, such as temperature, time, size and structure of the solid samples on the equilibration is demonstrated on the examples of the quantitative determination of vinyl chloride monomer in PVC, styrene in polystyrene, ethylene in polyethylene, ethylene oxide in a contact lens, halogenated hydrocarbons in coffee and residual solvents in drugs.

Gas chromatographic headspace analysis with pneumatic sampling

A derivation is given of the major equations describing the multiple headspace extraction process involving partial replacement of the gas phase by pneumatic sampling from pressurized heterogeneous systems. New modifications of the quantitative headspace analysis and concentration of compounds present in liquid and solid states, as well as new methods of chromatographic detector calibration based on the specific features of pneumatic gas sampling from vials pressurized with inert gas, are proposed.

Methods for the quantitative analysis of volatile halocarbons from aqueous samples by equilibrium headspace gas chromatography with capillary columns

Volatile halogenated hydrocarbons (halocarbons) from aqueous solutions are analysed by headspace gas chromatography with fused-silica capillary columns and an electron-capture detector with detection limits below the parts per billion level. Special emphasis is placed on quantitative determination. Calibration by the internal and external standard techniques and by the method of standard additions is discussed and compared with the multiple headspace extraction procedure, which is based on a repeated headspace extraction of the sample.

Multiple headspace extraction—A procedure for eliminating the influence of the sample matrix in quantitative headspace, gas chromatography

A stepwise gas extraction procedure is described for the quantitative gas chromatographic analysis of volatile compounds in solid and liquid samples. This procedure is a modification of the usual headspace analysis and can be carried out with the same equipment, provided a pressure and time controlled sampling system is used. This procedure is called ‘Multiple Headspace Extraction (MHE)’ therefore. This method has first been developed for the analysis of monomers in polymers and residual solvents in printed films, but it is shown that can be applied to various other sample types also including even liquid samples.

Quantitative analysis of residual solvents in food packaging printed films by capillary gas chromatography with multiple headspace extraction

A procedure for stepwise gas extraction at equal time intervals has been developed, which is called “multiple headspace extraction” (MHE), because it uses the same equipment as for a standard headspace analysis. The method is suitable as a calibration method for the headspace analysis of volatile trace compounds in solid samples which otherwise cannot be analysed quantitatively. A BASIC program has been used to perform the necessary calculations for quantitative determinations. The application of the MHE procedure is demonstrated on the example of the analysis of residual solvents in printed films which are used as food packaging material, and for the determination of vinyl chloride monomer in a PVC resin. Particularly for the solveny analysis a good glass capillary column is required to separate the complex mixtures which are used for printing the films.