Calibration of High-Pressure Pumps High-pressure reciprocating pumps are commonly enmuntered as the delivery systems for liquid chromate graphs. Most pumps have precise control over the flowrate of mobile phase and can indicate to the trained specialist whether a problem exists with the pumping cycle. There are certain circumstances, however, when instrumental failures are better assessed using a simple calibration procedure. Whenever inlet valves are disassembled or when the inlet tubes are removed from the mobile phases, air bubbles need to be dispelled since their presence in a pump head can affect retention times and baseline fluctuations may he enhanced (air bubbles in the analytical column can ruin resolution). In addition to these problems, the inlet and outlet check valve seals, and piston rod seals have a tendency to leak when worn out. A ~umrr's performance can be assessed, and the pump effectively calibrated across any range ifflowrates using water (ormobile phase) and a measuring cylinder of suitable volume (or an analytical balance if the specific gravity of the mohile phase is known). The measurine wlinder can a d as a reservoir. or as a mlleetion vessel as shown in the fieure. The oroeedure is especially useful forth& systems incorporating post-kolumn reactors, since the contrihutian ofeach reagekt stream to the total flowrate can he individually checked.
Michael N. Quigley Chevron Science Center University of Pittsburgh Pittsburgh, PA 15260
550
Journal of Chemical Education
