1. W. Buchberger, Z. Frezenius, Anal Chem. Electroanalysis, 354 (1996) 797.
2. M. Callull, R.M. Marce and F. Borrull, J. Chromatogr., 590 (1992) 251.
3. M. Callull, E. Lopez, R.M. Marce, J.O. Olucha and F. Borrull, J. Chromatogr., 589 (1992) 151.
4. C.X. Gao and I.S. Krull, J. Chromatogr., 515 (1990) 337.
5. T.J. O'Shea, S.M. Lunte and W.R. LaCourse, Anal. Chem., 65 (1993) 948.