Injector‐internal thermal desorption from edible oils performed by programmed temperature vaporizing (PTV) injection

Abstract

Injector-internal thermal desorption is a promising technique for the analysis of a wide range of food components (e.g., flavors) or food contaminants (e.g., solvent residues, pesticides, or migrants from packaging materials) in edible oils and fats or fatty food extracts. Separation from the fatty matrix occurs during injection. Using programmed temperature vaporizing (PTV) injection, the oily sample or sample extract was deposited on a small pack of glass wool from which the components of interest were evaporated and transferred into the column in splitless mode, leaving behind the bulk of the matrix. Towards the end of the analysis, the oil was removed by heating out the injector and backflushing the precolumn. The optimization dealt with the gas supply configuration enabling backflush, the injector temperature program (sample deposition, desorption, and heating out), separation of the sample liquid from the syringe needle and positioning it on a support, deactivation of the support surface, holding the plug of fused silica wool by a steel wire, and the analytical sequence maintaining adsorptivity at the desorption site low. It was performed for a mixture of poly(vinyl chloride) (PVC) plasticizers in oil or fatty food. Using MS in SIM, the detection limit was below 0.1 mg/kg for plasticizers forming single peaks and 1 mg/kg for mixtures like diisodecyl phthalate. For plasticizers, RSDs of the concentrations were below 10%; for the slip agents, oleamide and erucamide, it was 12%. The method of incorporating PTV injection was used for about one year for determining the migration from the gaskets of lids for glass jars into oily foods.

Contamination of vegetable oils marketed in Italy by phthalic acid esters

“…was prepared in the laboratory (Fankhauser-Noti & Grob, 2006). About 2 mg plug of fused silica wool was positioned in the centre and kept in place by a 0.3 mm steel wire.…”

“…The GC-MS analytical method applied in this study was described by Fankhauser-Noti and Grob (2006). It is based on direct injection of the diluted oil, injector-internal thermal desorption of the PAE in a programmed temperature vaporizing (PTV) injector and backflush to remove the bulk components of the oil from the pre-column and the injector liner.…”

Migration of plasticizers from the gaskets of lids into oily food in glass jars: a European enforcement campaign

“…Plasticizers detected in the gasket at a concentration of at least 0.5 g/100 g were analyzed in food in Zurich. The methods applied were mentioned in the Introduction [17][18][19][20][21].…”

“…For the analysis of the monomeric plasticizers, such as phthalates and acetylated monoglycerides, a GC method with detection by mass spectrometry (MS) was developed. The solutes of interest were separated from the sample matrix (mainly oil) using injector-internal thermal desorption in a programed temperature vaporizing (PTV) injector [19]. The most difficult task was the determination of polyadipates, as these consist of mixtures varying in the alcohol moiety, the molecular mass distribution and the end capping.…”

Use of atmospheric pressure solids analysis probe time‐of‐flight mass spectrometry to screen for plasticisers in gaskets used in contact with foods

“…Of these, 74 (24%) were reported to contain either non‐authorised plasticisers or the migration into food exceeded legal limits. The gaskets were extracted with solvent and then analysed with and without trans‐esterification by GC/flame ionisation detection (FID) methods …”