Injector‐internal thermal desorption from edible oils. Part 2: Chromatographic optimization for the analysis of migrants from food packaging material

Abstract

Injector-internal thermal desorption from edible oil or fat is a convenient sample preparation technique for the analysis of solutes in lipids or extracts from fatty foods. The injector temperature is selected to vaporize the solutes of interest while minimizing evaporation of the bulk material of the oil. This technique has been in routine use for pesticides for some time. Now its potential is explored for migrants from food contact materials, such as packaging, into simulant D (olive oil) or fatty/oily food, which means extending the range of application towards less volatile compounds. The performance for high boiling components was investigated for diisodecyl phthalate (DIDP) and diundecyl phthalate (DUP). Since the injector temperature needs to be as high as 260degreesC, some bulk material of the oil enters the column and must be removed after every analysis. This is achieved by a coated precolumn backflushed towards the end of each analysis. Desorption of the solutes is particularly efficient in the initial phase, when a thin sample film is spread on the liner wall, and is largely determined by the diffusion speed in the oil after the latter has contracted to droplets. An increased carrier gas flow rate during the splitless period supports the transfer into the column. It is concluded that the technique is attractive for migrant analysis, with DUP being at the upper limit of the boiling point.

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

“…In two previous papers [1,2], the technique was explored for conventional vaporizing injection (the origin of the technique). Compared to this, PTV injection offers some advantages and drawbacks.…”

“…The technique elaborated for a conventional (isothermal) injector was characterized by the following elements [1,2]: (i) The sample is injected by band formation, i. e., suppressing thermospray from partial solvent evaporation in the syringe needle [9]. (ii) Conditions ensure that the sample liquid is deposited on the liner wall, which means the use of solvents of a boiling point sufficiently high to avoid rejection of the sample liquid by a cushion of vapor, and oil concentrations not exceeding 20-30% in order to avoid squirting.…”

“…Thermal desorption from edible oil in a conventional vaporizing GC injector [1,2] was described as a simple technique for the analysis of compounds of up to rather high boiling points in oils and fats or extracts of fatty foods. The oil-containing solution is deposited on the wall of the injector liner.…”

Injector‐internal thermal desorption from edible oils. Part 1: Visual experiments on sample deposition on the liner wall

“…Part 1 reports experiments on optimizing the deposition of the sample on the liner wall using advanced visual observation methods. In Part 2 [23], desorption was optimized for higher-boiling solutes through chromatographic experiments.…”

Volatile Compounds in Australian Olive Oils

“…The situation is complicated as many volatile compounds and particularly hydrocarbons can be present in virgin olive oils either naturally or as contaminants (Pena et al, 2004). Moreover, volatile compounds may also be lost from an oil either to the atmosphere or due to absorption by packaging materials (Fiselier et al, 2005).…”