Normal Phase Applications

Valves for Normal Phase Applications (G7104A/C, G7120A)

Current passive inlet valves and outlet ball valves used with Agilent Infinity and Infinity II/III pumps do not work well while running nonpolar solvents for normal phase applications (for example, hexane and heptane). With such applications, pressure drops could be observed. They are the result of particles in insulating solvents, electrostatically charging up, and sticking to the nonconductive ruby balls inside the standard valves, such that the valves no longer close properly (could take just hours). For normal phase applications, a second type of valve is available. These valves use a new material for valve balls, which is a conductive ceramic. The ceramic balls do not charge up electrostatically and show good performance in normal phase applications. The valves are marked with "N" to stand for normal phase. Agilent recommends using these valves for (and only for) normal phase applications.

To avoid changing to the Type N valves when running critical solvents, it is possible to increase the conductivity of the mobile phase, by adding 5 % of a miscible, polar solvent. In general, isopropanol is a good choice.

No design change has been done for active inlet valves, which have already been used successfully for normal phase applications in 1260 Infinity I/II/III pumps.

Seals for Normal Phase Applications

For running normal phase applications on Agilent Infinity III pumps, yellow PE seals are required as piston seals. By default, 1290 Infinity, 1290 Infinity III, and 1260 Infinity III Flexible Pumps use ceramic pistons and yellow PE seals as piston seals. 1260 Infinity I/II/III pumps use sapphire pistons and black PTFE piston seals in a standard configuration. If using black PTFE seals with normal phase applications, the black PTFE seals wear and generate small particles. Such particles can clog valves and other parts in the flow path. When running normal phase applications on 1260 Infinity I/II/III pumps, the piston seals have to be changed to yellow PE seals. For optimum performance, PE seals should be replaced during preventive maintenance.