Peter Dipl Ing Pospisil

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

SummaryVolatile 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.

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

Abstract 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.

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

Abstract 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.

Ionization detector for gas chromatography with switchable selectivity for carbon, nitrogen and phosphorus

Abstract An ionization detector for gas chromatography is described, the selectivity of which can be changed such that it can be operated as a universal detector with the same properties as a flame-ionization detector, as a specific phosphorus detector and as a selective detector for both nitrogen and phosphorus. The last operational mode is also used for operation as a selective nitrogen detector. The changeover between all three operational modes is rapid and needs no manipulation of the detector itself, as all necessary operations are effected at the control unit only.