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Silylating reactions using hexamethyldisilazane (HMDS) as an alternative in the analysis of ambers

From the Old ages, the Amber’s unique physical properties have been exploited in the production of tools, ornaments and works of art. The use of derivatisation reagents that transform the polar pyrolysis products into less polar and more volatile compounds, improves the analytical performance and the detection limits of the technique. Tetramethyl ammonium hydroxide (TMAH) allows hydrolysis and methylation to be obtained simultaneously and is thus widely used derivatisation reagent.

Hexamethyldisilazane (HMDS)

Recently, silylating reactions using Hexamethyl Disilazane (HMDS) have been proposed as an alternative in the analysis of ambers. HMDS proved its potential with respect to the strongly alkaline TMAH reagent. Actually, the main limitations of this derivatizing reaction are related to the occurring of secondary reactions: particularly, decarboxylation reactions undergone by carboxylic acids and the formation of dehydration products and other by-products produce pyrograms of difficult interpretation. Moreover, TMHA can also induce decomposition of the stationary phase of the gas chromatographic column.

In addition, thermal desorption-gas chromatography coupled with mass spectrometry detection (TD-GC/MS) has been used to investigate the volatile compound fractions from ambers with a focus on Romanite (Romanian amber) and Succinite from several regions in Northern Europe and Baltic area.

This paper presents a study on archaeological and artistic amber objects using an optimised analytical technique based on pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS) and derivatisation in situ with hexamethyldisilazane (HMDS).