Sequential determination of titratable acidity and tartaric acid in wines by flow injection spectrophotometry

Abstract

A flow injection manifold is proposed for the sequential determination of titratable (total) acidity based on a pseudotitration and of tartaric acid based on the formation of a coloured vanadate complex. The method involves in-line dialysis prior to injection to avoid interference from the sample background absorption in the spectrophotometric detection. The changes in the colour of both reactions were monitored using two flow cells aligned in the optical path of a single spectrophotometer. Wine samples were analysed without any sample pre-treatment; table wines in the range 1–10 g l^–1 (total acidity) and 0.5–4 g l^–1 (tartaric acid) and port wines in the range 1–8 g l^–1 (total acidity) and 0.5–5 g l^–1 (tartaric acid). Sixteen samples can be measured per hour, and the results were comparable to those obtained by reference procedures for both determinations. RSDs (n = 10) generally lower than 3% were obtained.

References

1. M. A. Amerine and C. S. Ough, Methods for Analysis of Must and Wines, Wiley, New York, 1980.
2. B. F. Pilone and H. W. Berg, Am. J. Enol. Vitic., 1965, 16, 195.
3. Office International de la Vigne et du Vin (OIV), Recueil des Méthodes Internationales d'Analyse des Vins et des Moûts, OIV, Paris, 1978.
4. Official Methods of Analysis of the Association of Official Analytical Chemists, AOAC, Gaithersburg, MD, 16th edn., 1997.
5. O. Yu. Berezin, Ya. I. Tur'yan, I. Kuselman and A. Shenhar, Talanta, 1995, 42, 507.
6. G. Hill and A. Caputi, Jr., Am. J. Enol. Vitic., 1970, 21, 195.
7. G. J. Pilone, Am. J. Enol. Vitic., 1977, 28, 104.
8. L. Almela, I. Lázaro, J. M. López-Roca and J. A. Fernández-López, Food Chem., 1993, 47, 357.
9. M. Peris-Tortajada, A. Maquieira and R. Puchades, Am. J. Enol. Vitic., 1993, 44, 118.
10. F. Lázaro, M. D. Luque de Castro and M. Valcárcel, Analyst, 1986, 111, 729.
11. F. J. Krug, H. Bergamin F^o and E. A. G. Zagatto, Anal. Chim. Acta., 1986, 179, 103.
12. M. Valcárcel and M. D. Luque de Castro, Flow-Injection Analysis, Principles and Applications, Ellis Horwood, Chichester, 1987.
13. J. L. F. C. Lima, O. B. A. O. Neves and A. O. S. S. Rangel, in Automatic Control of Food and Biological Processes, ed. Bimbenet, J. J., Dumoulin, E., and Trystram, G., Elsevier, Amsterdam, 1994, pp. 67–74.
14. J. Ruzicka, E. H. Hansen and H. Mosbæk, Anal. Chim. Acta., 1977, 92, 235.
15. G. L. Long and J. D. Winefordner, Anal. Chem., 1983, 55, 712A.
16. J. C. Miller and J. N. Miller, Statistics for Analytical Chemistry, Ellis Horwood, Chichester, 3rd edn., 1993.