Optimization and Validation of a Headspace Solid-Phase Microextraction with Comprehensive Two-Dimensional Gas Chromatography Time-of-Flight Mass Spectrometric Detection for Quantification of Trace Aroma Compounds in Chinese Liquor (Baijiu)

Abstract

The detection of trace aroma compounds in samples with complex matrices such as Chinese liquor (Baijiu) requires a combination of several methods, which makes the analysis process very complicated. Therefore, a headspace solid-phase microextraction (HS-SPME) method coupled with two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS) was developed for the quantitation of a large number of trace compounds in Baijiu. Optimization of extraction conditions via a series of experiments revealed that dilution of the alcohol content of 8 mL of Baijiu to 5%, followed by the addition of 3.0 g of NaCl and subsequent SPME extraction with DVB/CAR/PDMS fiber coating over 45 min at 45 °C was the most suitable. To check the matrix effects, various model Baijiu matrices were investigated in detail. The quantitative method was established through an optimized model synthetic solution, which can identify 119 aroma compounds (esters, alcohols, fatty acids, aldehydes and ketones, furans, pyrazines, sulfur compounds, phenols, terpenes, and lactones) in the Baijiu sample. The developed procedure provided high recovery (86.79–117.94%), good repeatability (relative standard deviation < 9.93%), high linearity (R2 > 0.99), and lower detection limits than reported methods. The method was successfully applied to study the composition of volatile compounds in different types of Baijiu. This research indicated that the optimized HS-SPME–GC×GC-TOFMS method was a valid and accurate procedure for the simultaneous determination of different types of trace compounds in Baijiu. This developed method will allow an improved analysis of other samples with complex matrices.

Retronasal sensory characterization of aroma compounds in Baijiu by detection threshold measurement, retronasal OAVs, and time‐intensity evaluation

“…Quantification by HS-SPME-GC × GC-TOFMS HS-SPME-GC × GC-TOFMS analysis was used to quantify 30 aroma compounds following a previously published procedure with minor modifications (Mu et al, 2021). The Baijiu sample was diluted to the 5% v/v ethanol concentration with Millipore water.…”

“…Each sample was spiked with a mixed solution of internal standards (ISs), containing 175.61 µg/L of 2-phenylethyl acetate-d3 (IS2), 164.48 µg/L of (R)−2-methylbutyric acid-d3 (IS5), 84.86 µg/L of acetophenone-α,α,α-d3 (IS6), 160.41 µg/L of 2-methylpyrazine-d6 (IS7), 41.47 µg/L of 3-methyl-d3thiopropanal (IS8), 13.00 µg/L of isopropyl disulfide (IS9), 131.73 µg/L of 2-methoxyphenol-d3 (IS11), and 32.06 µg/L of (±)-linalool-d3 (IS13). To decrease matrix effects and generate a matrix identical to the real Baijiu, a simulated Baijiu solution was prepared according to Mu et al (2021) with minor modifications: 2121.70 mg/L of ethyl acetate, 3052.32 mg/L of ethyl lactate, 754.07 mg/L of 1-propanol, 255.52 mg/L of isoamyl alcohol, and 1671.36 mg/L of acetic acid were added to a 50% v/v ethanol aqueous solution, and lactic acid (AR Grade, Sinopharm Chemical Reagent Co., Ltd., Shanghai, China) was added to adjust the pH to 4.0. Standard solutions with different concentration gradients were subsequently prepared by twofold dilution with the 50% v/v ethanol aqueous solution, and the standard curves of each compound were drawn to quantify each aroma compound accurately.…”

Foods and Contaminants Analysis Using Multidimensional Gas Chromatography: An Update of Recent Studies, Technology, and Applications

“…An example includes quantitative analysis of trace compounds in Baijiu using HS-SPME-GC×GC−TOFMS. 134 Matrix effects were evaluated using a model solution to investigate competitive adsorption among different classes of compounds. The reported method employed 6 internal standards (ISs), 3 of which were isotopically labeled ISs; the method was validated by linearity, R 2 coefficients, limit of detection (LOD), limit of quantification (LOQ), intra-and interday precision, fication using deuterated IS with a similar validation performed.…”

“…For alcoholic beverages, in addition to typical wine and whiskey samples, local specialty alcoholic beverages, such as Baijiu (fermented sorghum or other grains), − Huangjiu (Chinese rice wine), , Tokaj wine (Slovakia), , and Syrah wine (Brazil), have been increasingly reported for MDGC applications over the past three years with fewer reports on tea, coffee, and fruit juice. According to Table , a majority of the reported applications aim to profile sample volatiles using GC×GC for general characterization or identify markers and/or evaluate the correlation between chemical compounds and organoleptic attributes of aroma using electronic nose (e-nose), 1DGC–O, and/or MDGC–O.…”

“…Thus, there is a need to ensure that matrix effects are taken into account. An example includes quantitative analysis of trace compounds in Baijiu using HS-SPME-GC×GC–TOFMS . Matrix effects were evaluated using a model solution to investigate competitive adsorption among different classes of compounds.…”