Applications of a portable capillary electrophoresis instrument in environmental science

Capillary electrophoresis (CE) is a widely-used separation technique for the analysis of
ionic species. It has crucial advantages due to high efficiencies given that small
differences in ion mobility are often sufficient for the resolution. The key features of the
CE instrument such as portability, rapidity of analysis and the need for only a small
sample volume offer the potential to facilitate future work of environmental scientists.
This thesis presents new applications of a portable CE instrument in the environment,
including the associated sampling techniques and measurement protocols.
(i) A new method for the extraction and analysis of lake sediment pore water was
developed. The extraction of the pore water from the sediment core was performed with
filter tube samplers. Samples were immediately injected and measured by CE. All major
cations and anions could be separated at once including the redox sensitive Fe(II)
without any sample pretreatment. Along with fast injection, this prevents samples from
alterations and contaminations. Sample volumes of only 20 μL allowed a high spatial
resolution of the pore water profile, even with low water content.
(ii) In a next step, the new method was applied in the field at Lake Baikal. The CE
instrument was thus carried by cabin luggage in the plane and assembled in improvised
laboratory containers at the shore of the lake. The pore water analysis was performed
immediately after coring. High-quality data enabled the explanation of the formation
and transformation of very special iron (III) and manganese (IV) oxide layers, which are
buried in the reducing part of the sediment. The analysis of Fe (II) and Mn (II) allowed
the determination of sharp redox boundaries. Overall, the high-quality data from on-site
measurement eliminated doubts concerning artefacts from previous measurements when
core squeezing and sample pretreatment had to be practiced.
(iii) Besides the analysis of pore water, another challenging field in environmental
science involves the surface analysis of rocks and biofilm. Thereby, surface processes
are studied in terms of weathering, initial soil formation, as well as growth and vitality
of microorganism. We developed a new method for the quantification of mobile ions
and adenosine triphosphate (ATP) on surfaces. For the collection of available ions and
ATP, a single drop of pure water was spread on the surface of the mineral or lichen and
recollected for the analysis by CE and a luminometer, respectively. The heterogeneity of
granites and the effect of wetting and freezing and thawing was shown on bare rock
surfaces. On lichen, the effect of humidity and age on their vitality was demonstrated.