On-line Trace Enrichment: Acidic Alumina

[I] Snelleman, W., Rains, T. C., Yee, K. W., Cook, H. D., and Menis, O., Anal. Chem. 42, 394 (1970). [2] Epstein, M. S., and O'Haver, T. C., Spectrochim. Acta 30B, 135 (1975). [3] Epstein, M. S., and Winefordner, J. D., Prog. Analyt. Atom. Spectrosc. 7, 67 (1984). [4] McLeod, C. W., Cook, 1. G., Worsfold, P. J., Davies, J. E., and Queny, J., Spectrochim. Acta 40B, 57 (1985). [5] Cook, 1. G., McLeod, C. W., and Worsfold, P. J., Anal. Proc. 23, 5 (1986). [6] Deardorff, E. R., Private Communication, National Bureau of Standards, March 1981. [7] Smith, M. V., and Burke, R. W., Private Communication, National Bureau of Standards, August 1987. [8] Wittman, A., and Schuster, L., Spectrochim. Acta 42B, 413 (1987). [2,3]. In the experiment relatively large volumes of sample are passed through a microcolumn in the flow injection (FI) manifold and retained analytes are subsequently eluted by injection of a small volume of eluent. Activated alumina offers a novel route for analyte preconcentration since it can function both as an anion and a cation exchanger depending upon solution pH. Under acidic and basic conditions alumina exhibits a high affinity for oxyanions and cations, respectively: