Single-drop microextraction followed by in-syringe derivatization and gas chromatography-mass spectrometric detection for determination of organic acids in fruits and fruit juices.

A simple analytical procedure based on single-drop microextraction combined with in-syringe derivatization and GC-MS was developed for determination of some phenolic acids in fruits and fruit juices. Cinnamic acid, o-coumaric acid, caffeic acid, and p-hydroxybenzoic acid were used as model compounds. The analytes were extracted from a 3-mL sample solution using 2.5 microL of hexyl acetate. The extracted phenolic acids were derivatized inside the syringe barrel using 0.7 microL of N,O-bis(trimethylsilyl)acetamide before injection into the GC-MS. The influence of derivatization conditions on the yield of in-syringe silylation was studied. Experimental SDME parameters such as selection of organic solvent, solvent volume, extraction time, extraction temperature, pH, and ionic strength of the solution on the extraction performance were studied. The method provided fairly good precision for all compounds (2.4-11.9%). Detection limits were found to be between 0.6 and 164 ng/mL within an extraction time of 20 min in the GC-MS full scan mode.