Development and validation of a high performance liquid chromatography-diode array detection method for the determination of aging markers in tequila.

A solid-phase extraction procedure followed by analysis by high performance liquid chromatography (HPLC) with UV-vis photodiode array detection (DAD) is proposed to simultaneously determine 11 aging markers in tequila. The method showed good intraday (n=5) and interday (n=3) precision, RSD<1.6% in both cases, for each of the identified compounds. The calibration curves were linear at the tested ranges (R(2)>0.999). Good recoveries (84.2-108.5%) were obtained for 10 of the 11 compounds studied; and the LOD and LOQ ranged from 0.62 to 4.09 microg/mL and 1.9-12.4 microg/mL, respectively. The proposed methodology was applied to a set of 15 authentic tequila samples grouped by aging state (blanco, reposado and añejo). An ANOVA analysis combined with discriminant analysis with stepwise backward variable selection was used to differentiate between the various aging groups based on their oak related compounds content.

Detection of bacterial infection of agave plants by laser-induced fluorescence.

Greenhouse-grown plants of Agave tequilana Weber var. azul were inoculated with Erwinia carotovora, the causal agent of stem soft rot. We investigated the laser-induced fluorescence (LIF) of agave plants to determine whether LIF can be used as a noninvasive sensing tool for pathological studies. The LIF technique was also investigated as a means of detecting the effect of the polyamine biosynthesis inhibitor beta-hydroxyethylhydrazine as a bactericide against the pathogenic bacterium Erwinia carotovora. A He-Ne laser at 632.8 nm was used as the excitation source, and in vivo fluorescence emission spectra were recorded in the 660-790-range. Fluorescence maxima were at 690 and 740 nm. The infected plants that were untreated with the bactericide showed a definite increase in fluorescence intensity at both maxima within the first three days after infection. Beginning on the fifth day, a steady decrease in fluorescence intensity was observed, with a greater effect at 740 than at 690 nm. After 30 days there was no fluorescence. The infected plants that had been treated with the bactericide showed no significant change in fluorescence compared with that of the uninfected plants. The ratio of fluorescence intensities was determined to be F 690 nm/F 740 nm for all treatments. These studies indicate that LIF measurements of agave plants may be used for the early detection of certain types of disease and for determining the effect of a bactericide on bacteria. The results also showed that fluorescence intensity ratios can be used as a reliable indicator of the progress of disease.