UV detection of derivatized carbonyl compounds in rain samples in capillary electrophoresis using sample stacking and a Z-shaped flow cell

The feasibility of trace analysis of carbonyl compounds in size classified rain samples by capillary electrophoresis (CE) is demonstrated. Limits of detection (LOD) in the range of 170-300 nmol/l were reached after derivatization of aldehydes with 5-(dimethylamino)-naphthalene-1-sulfon-hydrazide (dansylhydrazine, DNSH) and using both a Z-shaped flow cell (ZFC) and sample stacking. Advantages and disadvantages of the detection using a ZFC providing an optical path length of 3 mm were examined. The improvement of LOD by factors of 20 and a loss of resolution for example from 4.7 (on-column detection) to 2.5 (ZFC) is due to the extended light path. Furthermore an enrichment of the analytes is possible by sample stacking. Problems according to the higher susceptibility of the detection system to disturbances in the electrolyte system could be solved using a special sample injection technique.