Chromatographic separation method and associated apparatus

DETAILED DESCRIPTION The present invention has met the above-described need by providing means for effectively controlling the flow rate through a column such as a capillary or packed column in supercritical fluid chromatography without requiring replacement of a restrictor.
This is accomplished by simultaneous flow and pressure programming.
A high pressure pump provides a fluid to an injector which in turn introduces a sample into the fluid and delivers the fluid containing sample to a column which is positioned inside an oven which serves to maintain the fluid sample at the desired temperature.
A flowmeter may be interposed between the pump and injector in order to monitor the flow rate.
A portion of the fluid sample separates as it passes through the column after which the fluid passes through a first restrictor.
The high pressure pump has a second outlet for delivering the fludd (without sample) to a pressure control inlet which is positioned between the first restrictor and the nozzle.
By adjusting the pressure of the fluid introduced at the pressure control inlet, the flow rate of the fluid sample through the column may be controlled.
A second restrictor may be interposed between the pressure control inlet and the nozzle in order to provide a further flow control.
Detector means may be positioned so as to receive fluid emerging from the second restrictor in order to analyze the same.
A control valve, which may be controlled by any suitable means, is adjustable in order to control the pressure of the fluid entering the pressure control inlet.
A transducer may also be provided so as to monitor the pressure of the fluid exiting the control valve and to thereby provide feedback information to the controller to permit further adjustments.
Where the detector means is a flame detector, it may be advantageous to increase the temperature of the auxiliary fluid such that it compensates for reduction in temperature of the column effluent fluid as it emerges from the column.
This results in the desired reduction in pressure before entry into the flame detector while avoiding the hereinbefore discussed problems