Isolation of free phenolic compounds from arboreal leaves by use of the Florisil/C18 system

In studies of the phenolic compounds present in leaves and needles, GC and GC-MS have so far been applied only sporadically. This is probably because of the greater difficulties encountered in preparing the samples for this method than those used for liquid chromatography. When preparing a sample for gas chromatography the analyst is faced with two difficult stages-separation of the compound from the matrix without losses (stage 1) so that the final sample can be derivatized to make it suitable for analysis on a non-polar capillary column of the gas chromatograph (stage 2). This paper presents a procedure for extraction of phenolic compounds from the matrix by means of a Florisil/C-18 sorbent system and their analysis by GC. After passage through the adsorbents the recovery ranges from 32% for ferulic acid to 88% for gentisic acid. It was found that this extraction method and the GC analysis are very precise (particularly for samples of a mass <1 g) and can be used for quantification. The high-precision quantification of 15 phenolic acids, shikimic acid, and six other compounds present in pine needles has been achieved. The conditions used for GC analysis and construction of calibration curves for quantitative determination are given.