RESUMO
A pressure-controlled on-column injection method was developed for microcolumn liquid chromatography. The system was assembled from a syringe pump, a Model M-445 Six-Way Micro Selection Valve, a separation column and a UV detector. The injection volume could be regulated by changing the applied pressure and/or the sample loading time. The system was evaluated in the ion-exchange mode. The system was applied to the determination of anions in river-water samples.
RESUMO
Split flow and bypass flow systems were assembled using Nano Y Connectors with low dead volume commercially available for capillary liquid chromatography (LC). The split ratio could be controlled by changing the dimension of restriction tubing and applied back pressure to the restriction tubing. The split flow system allowed us to use valve injectors and pumps commercially available for capillary LC. The reproducibility of the present split flow system was acceptable. The relative standard deviation for six successive measurements was 0.4% for the retention time, whereas that for the peak height and peak area was 1-3% depending on the analytes. The bypass flow system uses two Nano Y Connectors, where the eluent split at the first Nano Y Connector, which is located in the inlet of the separation column, is merged again into the effluent from the column at the second Nano Y Connector. The bypass flow system could avoid on-column detection and allowed us to use flow cells, leading to an approximate three times improvement in signal-to-noise. The present flow systems were evaluated by using aromatic hydrocarbons and alkylbenzenes as test analytes.
