## 3 Results
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline  & & \multicolumn{8}{c}{**Concentration (mg/L)**} \\ \hline
**Sample Number** & **1** & **3** & **8** & **10** & **15** & **16** & **17** & **18** & **25** & **27** & **Peaks Utilized** \\ \hline
**Aroma Style** & **Light** & **S**uce & **S**uce & **Light** & **Light** & **S**uce** & **Light** & **Light** & **Light** & **S**uce** & **Shift (ppm) \& Multiplicity** \\ \hline Methanol & 87 & 128 & 13 & 0 & 80 & 99 & 51 & 87 & 109 & 128 & 3.38 (s) CH3 \\ Ethanol g/L & 48.5 & 43.7 & 30.1 & 33.2 & 45.1 & 44.1 & 43.5 & 53.5 & 45.5 & 41.5 & 1.16 (s) CH3 \\ Ethanol \(\approx\)/e\(-\)NMR & 59.4 & 53.5 & 37.0 & 40.7 & 58.2 & 54.0 & 53.3 & 65.7 & 58.7 & 50.8 & - \\ Ethanol \(\approx\)/e\(-\)Label & 58.0 & 53.0 & 38.0 & 40.0 & 56.0 & 53.0 & 53.0 & 66.0 & 56.0 & 52.0 & - \\ Isopentational & 385 & 486 & 0 & 0 & 431 & 454 & 700 & 417 & 448 & 240 & 0.89 (d) CH3 \\
1-Propanol & 1017 & 1095 & 0 & 0 & 2711 & 611 & 284 & 1162 & 1010 & 393 & 0.88 (s) CH3 \\ Aortic Acid & 1107 & 1054 & 410 & 0 & 1190 & 1172 & 331 & 772 & 950 & 719 & 2.08 (s) CH3 \\ Lactic Acid & 333 & 1281 & 470 & 0 & 563 & 1405 & 9 & 27 & 346 & 771 & 3.36 (s) CH2 \\ Ethyl Acetate & 1778 & 1500 & 286 & 0 & 1760 & 1596 & 633 & 1266 & 993 & 763 & 41.2 (s) CH2 \\ Ethyl Lactate & 340 & 655 & 257 & 0 & 306 & 586 & 503 & 172 & 172 & 566 & 4.21 (s) CH2 \\ Ethyl Butyrate & 0 & 0 & 0 & 0 & 320 & 172 & 377 & 206 & 503 & 46 & 4.26 (s) CH2 \\ Ethyl Caporate & 0 & 284 & 397 & 0 & 0 & 1562 & 0 & 0 & 0 & 814 & 4.13 (s) CH2 \\ Furfural & 0 & 236 & 0 & 0 & 0 & 227 & 0 & 0 & 0 & 0 & 9.49 (s) CH \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Concentrations of ethanol and major congeners for 10 of the 30 baijiu samples analyzed. Figure 5: \({}^{1}\)H NMR—methyl region—stacked plot comparisons of 10 of 30 baijiu samples analyzed in this study. Sample 10 stands out as a potential counterfeit sample, as it only shows the presence of ethanol. No congeners are observed, as in the other samples. The numbered assignments are as follows: 1. lactic acid, 3. ethyl acetate, 8. acetic acid, 9. 1-propanol, 10. isopentanol. Having confirmed the ethanol concentration of 27 of the baijiu samples by \({}^{1}\)H qNMR, we decided to utilize the 27-sample dataset to produce a Partial Least-Squares (PLS) regression model using the FTIR-ATR data utilized in the PCA analysis. Figure 9 shows a superposition plot of the 27 FTIR spectra obtained with an expansion showing the specific peaks at 1044 and 1086 cm\({}^{-1}\) that can be attributed to the C-O stretch of ethanol [30; 31]. Figure 10 shows the quality of the resulting PLS regression model that correlates the \({}^{1}\)H qNMR ethanol content to that predicted by FTIR-ATR. The model shows an excellent correlation (R\({}^{2}\) = 0.991) and an SECV of 0.75 %ABV, which is close to the standard error associated with the NMR correlation with the label values provided on the baijiu bottles. The correlation was obtained with two latent variables and involved a cross-validation process involving a Venetian blind approach with five data splits. Figure 6: \({}^{1}\)H NMR—ethyl ester region—stacked plot comparisons of 10 of 30 baijiu samples analyzed in this study. Sample 10 stands out as a potential counterfeit sample, as it only shows the presence of ethanol. No congeners are observed, as in the other samples. The numbered assignments are as follows: 1. lactic acid, 2. ethyl lactate, 3. ethyl acetate, 7. acetaldehyde, 13. higher esters CH\({}_{2}\) adjacent to carboxyl—butyric, caproic. Figure 8: Comparison of qNMR-calculated ethanol content (%ABV) and the stated label content. Figure 7: Superimposed \({}^{1}\)H NMR spectra showing a suspected counterfeit baijiu (sample 10, green) containing only ethanol and no congener chemistry compared to a typical baijiu (sample 3, red), which shows the obvious congener signals from furfural (peaks 6.7 to 9.5 ppm), ethyl ester (4.0–4.5 ppm), acetaldehyde, acetic acid (2–2.5 ppm), and higher alcohols (0.85–0.95 ppm).