Actas de congresos
Monosegmented Flow Titrator
Analytica Chimica Acta. , v. 438, n. 1-2, p. 67 - 74, 2001.
De Aquino E.V.
An automatic titrator based on the monosegmented flow approach is described. The flow titrator is unique in fulfils the definition of IUPAC for the titration technique. This means that, the flow analyser produces a complete titration curve and is capable using the equivalence point concept for determination of the titrant concentration without the use of any calibration, usually employed in similar systems. The titrant is added to the sample monosegment by using a syringe driven by a step motor. The titrant is added with a precision of ±0.5 μl. The main advantage of the proposed flow titrator is in the fact that, if necessary, only one aliquot (100-200 μl) of the sample need be employed to make a complete titration with a suitable titrant solution. This feature has been demonstrated by titrating Fe(II) and H2O2 solutions with KMnO4. However, a complete titration is not the fastest way to find the end point. A successive approximations algorithm is described which allows the end point to be achieved in, at most, eight steps. The novelty of this approach is that the sample solution does not need to be discarded when titrant addition do not exceed the end point. The proposed flow titrator has been evaluated for spectrophotometric, indicator based, titrations of strong and weak acids and for titration of hydrogen peroxide in commercial products using KMnO4. The results show that the system can, on average, perform one titration each 2 min, when employing the successive approximations algorithm. The precision and accuracy for HCl or acetic acid titrations (concentration range 0.0025-0.100 moll-1), using phenolphthalein as indicator, and H2O2, using the self indicating KMnO4 titrant, was from 0.5 to 2%. Because the proposed system resembles a real titrator in all aspects, all detection techniques employed for conventional titrations can be, in principle, also employed with this flow manifold. © 2001 Elsevier Science B.V.4381-26774Blaedel, W.J., Laessig, R.H., (1964) Anal. Chem., 36, p. 1617Blaedel, W.J., Laessig, R.H., (1965) Anal. Chem., 37, p. 332Calatayud, J.M., Falcó, P.C., Abert, R.M., (1987) Analyst, 112, p. 1063Fleet, B., Ho, A.Y.W., (1974) Anal. Chem., 46, p. 9Nagy, G., Fehér, Z., Tóth, K., Pungor, E., (1977) Anal. Chim. Acta, 91, p. 7Ruzicka, J., Hansen, E.H., (1975) Anal. Chim. Acta, 78, p. 145Astrom, O., (1979) Anal. Chim. Acta, 105, p. 67Araújo, M.C.U., Santos, A.V., Honorato, R.S., Pasquini, C., (1997) J. Autom. Chem., 19, p. 157Taylor, R.H., Ruzicka, J., Christian, G.D., (1992) Talanta, 39, p. 285Taylor, R.H., Rotermund, J., Christian, G.D., Ruzicka, J., (1994) Talanta, 41, p. 31Chen, R., Ruzicka, J., Christian, G.D., (1994) Talanta, 41, p. 949Korn, M., Gouveia, L.F.B.P., Oliveira, E., Reis, B.F., (1995) Anal. Chim. Acta, 313, p. 177Martelli, P.B., Reis, B.F., Korn, M., Lima, J.L.F.C., (1999) Anal. Chim. Acta, 387, p. 165Honorato, R.S., Araújo, M.C.U., Lima, R.A.C., Zagatto, E.A.G., Lapa, R.A.S., Lima, J.L.F.C., (1999) Anal. Chim. Acta, 396, p. 91Pasquini, C., Oliveira, W.A., (1985) Anal. Chem., 57, p. 2575Raimundo I.M., Jr., Pasquini, C., (1997) Analyst, 122, p. 1039Brito, V.O., Raimundo I.M., Jr., (1998) Anal. Chim. Acta, 371, p. 317Ganzarolli, E.M., Lehmkuhl, A., Queiróz, R.R.R., Souza, I.G., (1999) Química Nova, 22 (1), p. 53De Koning, M.A., (1998), M.Sc. thesis, Chemistry Institute, UNICAMP, SP, BrazilHonorato, R.S., Araújo, M.C.U., Veras, G., Zagatto, E.A.G., Lapa, R.A.S., Lima, J.L.F.C., (1999) Anal. Sci., 15, p. 1Sandell, E.B., West, T.S., (1969) Pure Appl. Chem., 18, p. 429Raimundo I.M., Jr., Pasquini, C., (1993) J. Autom. Chem., 15, p. 227Horowitz, P., Hill, W., (1989) The Art of Electronics, 2nd Edition, , Cambridge University Press, Cambridge