Operation of an HPLC Instrument

Mobile phase storage The figure shows four reservoirs, one for each of up to four pure solvents [e.g., water (perhaps with pH controUing buffer), acetonitrile, methanol, tetrahydrofuran, etc.]. Note the use of inlet filters. Alternatively one could prepare the mobile phase mixture to the desired composition manually, and store it in a single reservoir. Operation at a single, constant mobile phase composition is called isocratic HPLC elution. 

Fill/drain valve There are many liquid transfer lines and components that the mobile phase passes through before it gets to the head of the column. The 

HPLC detectors Like GC, HPLC has a wide variety of detectors, universal or specific, destructive or nondestructive, mass flow or concentration responsive, and with even more chaHenging requirements for interfacing to spectrometers in hyphenated techniques. Tubing of even smaller bore than described earlier in item 5 is necessary to connect the effluent end of the column to the detector to avoid extra-column band broadening effects. Pressures are lower and high strength and density PEEK plastic may be used in place of stainless steel. 

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