Electrokinetic sample extraction and enrichment: a new method for the isolation of analytes from sludge-type matrices

Electrokinetic sample extraction and enrichment is introduced as a newly developed concept for the analysis of substances in sludge-type or paste-like matrices. It is based on electrokinetic transport phenomena as electromigration and electroosmosis occurring when an electrical field is applied to the fresh, wet samples. Problems usually associated to sample drying can be avoided, e.g., losses of volatile analytes or contamination. We have designed and built a suitable apparatus for electrokinetic sample extraction and enrichment. Appropriate operating conditions (field strength, buffer composition, concentration, and volume) were identified in experiments with an artificial sludge model and real-world lake sediments. A proof of principle of the method was provided by the electromigrative extraction and online enrichment on a solid-phase sorbent disk of an azo dye from a diatomaceous earth slurry. Electroosmotic extraction and enrichment of a cyanobacterial hepatotoxin at trace levels was finally investigated as an application example using lake sediments. Rather clean extracts were obtained even with high organic content sediment samples, as shown by high-performance liquid chromatography with diode array detection.