T. Wickstrom et al., Comparison study of five analytical methods for the fractionation and subsequent determination of aluminium in natural water samples, J ENVIR MON, 2(2), 2000, pp. 171-181
Five methods for aluminium fractionation used in different laboratories in
Norway and Finland were compared using six control, 75 soil water and 10 la
ke water samples. Different fractionation principles [cation exchange, form
ation of the Pyrocatechol Violet (PCV) or quinolin-8-ol (oxine) complex], t
ypes of cation exchanger [Amberlite (Na/H) or Bond Elut (H)], reaction time
(from 2.3 s), flow systems (flow injection analysis or segmented flow) and
determination principles (molecular absorption spectrometry or ICP-AES) we
re tested. Determination of the 'labile' fraction was strongly dependent on
the method used and the largest differences were observed between the ICP-
AES method with cation exchange (Bond Elut H form) and the 'quickly reactin
g' method (oxine, 2.3 s). Different flow systems, both using cation exchang
e and determination of the PCV complex but with different reaction times an
d an extra acidification step, resulted in large differences in the 'reacti
ve' and 'non-labile' fractions determined. However, the determination of th
e labile fraction gave similar results with both these methods. The two dif
ferent types of cation exchanger used (with and without pH buffering and wi
th different counter ions) in the ICP-AES methods resulted in differences,
mainly because of a smaller 'non-labile' fraction in the non-buffered syste
m. The two flow injection systems (oxine and PCV complexation) showed commo
n trends, which may be connected with the short reaction times used. Compar
ison with theoretical equilibrium calculations using the model ALCHEMI sugg
ested that the best correlation for the determination of the 'labile' fract
ion were obtained with the ICP-AES method with an Amberlite column.