Determination of Tannins in White Wines by Thermal Lens Spectrometry

Tannins in white wines were determined by reduction of the Folin-Ciocalteu reagent, extraction of the phosphomolybdenum blue produced into chloroform in the presence of a tetraalkylammonium salt, and thermal lens spectrometry (TLS). The TLS setup was pumped with a diode-array laser (60 mW, 818 nm), and the thermal lens effect was probed with a He-Ne laser in a crossed-beam configuration. Extraction was quantitative within the range 25-250 ng...