Comparison of Curie-point pyrolysis with tetramethylammonium hydroxide (TMAH) and base catalyzed methanolysys in leaf and root biomarker decomposition studies

Cutin and suberin have frequently been used as plant-part specific biomarkers in sediments and soils. The two most commonly used analytical methods described in the literature to study cutin and suberin are pyrolysis with tetramethylammonium hydroxide (TMAH) and base-catalyzed methanolysis with potassium hydroxide (KOH). Both methods are usually combined with gas chromatography (GC) to analyze and identify the resulting compounds. However, until now, a critical assessment of the compatibility of the results obtained by both methods was missing.

Here, we compared the two techniques on Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) roots and needles that decomposed for three years in litterbags. KOH methanolysis released a broader suite of long-chain alcohols, diols and mid-chain hydroxy-fatty acids, identifying 19 tissue-specific biomarkers, whereas pyrolysis with TMAH yielded 10 diagnostic compounds; only seven markers overlapped. The concentrations of analogous molecules decreased in different ways over time, preventing any generalizable conclusions from being drawn about the stability of the original biopolymers.Thus, the methods are complementary rather than interchangeable. Pyrolysis yields fewer, more temporally stable signals and requires substantially less sample preparation per analysis, making it well suited to quantitative source apportionment; by contrast, methanolysis involves multi-step sample preparation and provides richer structural detail that facilitates biomarker discovery across taxa and matrices.