ICP-MS multi-element profiles and HPLC determination of furanic compounds in commercial tequila

In this work, inductively coupled plasma mass spectrometry determination of Ag, As, Ba, Cd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Sb, Se, Tl, V, Zn, Th and U in commercial tequila has been accomplished. The samples were tenfold diluted (1% HNO3), ethanol (4% v/v) was added to multi-element calibration solutions and possible spectral interferences were controlled by the use of collision/reaction cell technology. The results obtained in the analysis of 40 brands showed low concentration levels of the elements, in agreement with actual Mexican regulations, except for copper. Statistically significant differences were found between the concentration levels of copper, molybdenum, mercury and thorium in 100% agave and mixed tequila brands. In search of parameters useful for discrimination between 100% and mixed tequila categories, 5-hydroxy-methylfuraldehyde, 2-furoic acid (2-FAC), 2-furaldehyde (2-FAL), 2-furylmethylketone (2-FMC), 5-methylfuraldehyde (5-MFA), syringaldehyde (SIR) were also determined, using simple and fast reversed phase chromatographic procedure. Principal component analysis was used as the variable reduction procedure. In the multivariate model obtained, a natural separation of 100%, mixed and aged tequilas has been observed in the space defined by the first three principal components that accounted for 94% of total system variability. The analysis of correlation revealed statistically significant direct relationship between 100% tequila and 2-FAL, 5-MFA, Cu (β = 0.781, p = 0.028; β = 0.688, p = 0.042; β = 0.664, p = 0.046, respectively), between mixed tequila and Hg, Th, Mo (β = 0.948, p = 0.000; β = 0.905, p = 0.002; β = 0.867, p = 0.012, respectively) and between aged tequila and SIR, 2-FAC (β = 0.937, p = 0.000; β = 0.889, p = 0.000, respectively). In conclusion, among 25 parameters initially selected, the above 8 (2-FAL, 5-MFA, Cu, Hg, Th, Mo, SIR, 2-FAC) could be useful in the multivariate discrimination between tequila categories.