On-Chip Integration of Sequential Ion-Sensing System Based on Intermittent Reagent Pumping and Formation of Two-Layer Flow

The coupling of antibody-, receptor-, or enzyme-based inhibition assays postcolumn to chromatographic systems provides biological detectors with extraordinary high sensitivity and specificity. Three monoclonal antibodies (MC10E7,AD4G2, M8H5)directed against microcystins and protein phosphatase 1 (PP1) were used as off-line detectors for the HPLC separation of microcystins and nodularin in comparison to UV detection. For HPLC/ ELISA coupling using antibody MCIOE7, a detection limit of 0.04 ng microcystin-LR was achieved. The provisional guideline value for microcystin-LR (1mug/L, WHO) could be monitored without prior sample concentration, in contrast to UV detection. Quantification of microcystinLR and two cross-reactants was demonstrated. Furthermore, cross-reactivity or enzyme inhibition of new microcystins, only available in small amounts, can be determined by this method. Using a cyanobacterial extract, HPLC/ ELISA coupling was compared to HPLC/UV and electrospray ionization mass spectrometry (ESI-TOFMS).