Evaluation of the full evaporation technique for quantitative analysis of high boiling compounds with high affinity for apolar matrices

• A full evaporation technique method was developed for various apolar matrices.
• Easy sample preparation for this type of matrices using full evaporation technique.
• No significant difference between matrix-matched and solvent-based calibration.
• Method showed excellent recovery and repeatability.

In order to reduce inaccuracies due to possible matrix effects in conventional static headspace-gas chromatography (sHS-GC), it is standard practice to match the composition of calibration standards towards the composition of the sample to be analysed by adding blank matrix. However, the latter is not always available and in that case the full evaporation technique (FET) could be a solution. With FET a small sample volume is introduced in a HS vial and compounds of interest are completely evaporated. Hence no equilibrium between the condensed phase and vapour phase exists. Without the existence of an equilibrium, matrix effects are less likely to occur. Another issue often encountered with sHS-sampling is that low vapour pressure compounds with a high affinity for the dilution medium show a limited sensitivity. FET has proven to be an appropriate solution to address this problem too.In this work, the applicability of FET for the quantitative analysis of high boiling compounds in different complex apolar matrices is examined. Data show that FET is an excellent tool to overcome matrix effects often encountered with conventional sHS analysis. The tested method shows excellent accuracy with recovery values around 100% as well as repeatability with RSD values around 1% for the quantification of high boiling compounds (bp > 200 °C) such as camphor, menthol, methyl salicylate and ethyl salicylate in various matrices. LOQ values were found to be around 0.3 μg per vial. Following validation of the technique, several topical pharmaceutical formulations like ThermoCream®, Reflexspray®, Vicks Vaporub® and Radosalil® were examined. For the latter, a comparison has been made with a sHS-method described in literature.