Semiautomatic flow-injection method for determination of volatile acidity in wines

A flow-injection (FI) method based on analytical pervaporation was assessed for its routine use in the determination of volatile acidity in winery laboratories. The new method was compared with both the official method and the Mathieu method, which is most often used in Spanish wineries, by testing 30 different wines, including young and aged, and sweet and dry wines from Montilla-Moriles appellation d'origine. The robustness of the new method was established, and then all 3 methods were studied in terms of range of linearity and regression of the calibration curve, repeatability, reproducibility, sensitivity, detection and quantitation limits (LOD and LOQ, respectively), and time of analysis. The FI method surpassed the Mathieu method in reproducibility and both the Mathieu and official methods in LOD and LOQ and sensitivity; it also required less personnel involvement and shorter analysis time. The statistical criteria established by the Office International de la Vigne et du Vin were applied to the data and the results obtained indicated that the differences between the analytical parameters of the 3 methods are not significant and can be applied indistinctly. The correlation of the methods was studied by taking them 2 by 2, and the corresponding equations, coefficients, and deviations confirmed the statistical results. Thus, the new method can be used in winery laboratories with clear advantages over its 2 counterparts (the routine and official methods).