Development of a Solid-Phase Microextraction-Gas Chromatography/Mass Spectrometry Method for Quantifying Nitrogen-Heterocyclic Volatile Aroma Compounds: Application to Spirit and Wood Matrices

Over wood aging, matured spirits developed a complex aromatic bouquet where roasted-like notes were often perceived. Since many nitrogen heterocycles were related to these olfactory nuances, a headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography-mass spectrometry was developed and validated to quantify them in both spirit and wood matrices. The various parameters affecting the extraction of the analytes from both spirit and wood samples were first investigated (i.e., fiber coating phase, dilution, pH and volume sample, adding salt, extraction time and temperature, and incubation time) to determine the best compromise for a single-run analysis of the whole set of studied compounds. Good linearity (R² > 0.99), repeatability, reproducibility, accuracy and low detection, and quantification limits were obtained, making this analytical method a suitable tool for routine analysis of the selected nitrogen compounds. Fifteen pyrazines, three pyrroles, and three quinolines were quantified in a series of oak wood and commercial spirit samples where some of them were identified for the first time. The significant impact of some barrel features and the spirit in-wood maturation step on the N-heterocycle profile in both matrices were finally discussed.