Usually multicapillary columns (MCC) are used at flow rates of a carrier gas close to 60 ml/min, which are typical for normal work of chromatographic detectors.
However some detectors require higher flow rates for their work. Such the detectors, for instance, are ion mobility spectrometers, atomic emission and molecular condensation nuclei detectors. As a rule there is an additional stream of the carrier gas in these detectors, which dilutes a gas mixture eluating from a column that results in decreasing the concentrations of substances and in lowering the sensitivity of analysis. MCC can use for their work both the usual and big flow rates of a carrier gas that enables to decrease or to eliminate the additional stream and to increase the sensitivity of analysis.
At the big flow rates MCC consisting of 60 - 80 μm capillaries have a temperate pressure difference (dP) and relatively high capability of separation.
The combination of a high permeability and separation capability of MCC is a unique for chromatographic columns.
Examples of separation of hydrocarbon mixtures are shown on the Figures.
The data were obtained on chromatographic systems with photoionization detector and multicapillary columns at 250C. Purified air was used as a carrier gas.
MCC, 220 mm long, 1200 capillaries, each of which has 40 μm inner diameter; phase OV-1; flow rate 500 ml/min; dP=1.2 atm.
MCC, 200 mm long, 1200 capillaries, each of which has 60 μm inner diameter; 0.3 μm film of OV-1; flow rate 500 ml/min; dP=0.6 atm
MCC, 250 mm long, 2200 capillaries, each of which has 80 μm inner diameter; 0.8 μm film of OV-1301; flow rate 1000 ml/min; dP=0.37 atm.
1 – acetone;
2 – ethyl acetate;
3 – benzene;
4 – toluene;
5 – butyl acetate;
6 – m-xylene;