Analysis of small volumes of soil solution by capillary electrophoresis

Capillary electrophoresis (CE) is suitable for the analysis of cations and anions, including organic acids, in soil solution. In the concentration range typical for soil solutions, the standard deviation of the linear calibration function is, with the exception of NH₄/⁺ and Na⁺ (≃ 12%), better than 6%. Using drift correction procedures, CE is applicable for routine analysis. The advantage of this analytical technique is the minimal sample consumption of about 5 to 10 nL per analytical run, which enables new approaches for soil solution collection and analysis on a microscale level. As an example, a podzol profile was covered by a vertical matrix of 6 x 10 microlysimeters (sampling distance 2 cm). High resolution maps of soil solution chemistry showed, that, although some solutes had concentrations related to soil horizons (UV as measure for DOC, SO4₄/^2-, Al³⁺), in general there was little correlation between the clearly visible soil horizon borders and concentration isolines. For all solutes analyzed even within soil horizons marked concentration gradients could be observed.