HPLC Detector Design and Operation

Sections 13.1.1 and 13.1.2 described the stationary-phase column and the mobile-phase liquid, respectively. Section 13.1.3 described how these and other HPLC instrument components are connected together and operated. The last item therein, number 8, detectors, covers such a broad and important variety of devices that another subsection will be required to describe them. Many of the principal featnres of HPLC detector operation are those described for GC detectors in the introduction in Section 12.7. The stndent is enconraged to reread that section. Only item number 4 in Section 12.7, is peculiar to GC. An analogons feature in HPLC would be postcolumn derivatization, which will be treated later in Section 13.1.5. As in the GC chapter, hyphenated HPLC techniques are discussed separately in Section 13.1.6. 

RI Characteristics. Universal nondestmctive concentration detector relatively insensitive requires thermostatting and useable only with isocratic HPLC separations. 

ELSD Characteristics. Universal destructive mass-flow detector sensitive requires auxiliary gas useable with isocratic or gradient mobile phases but with no buffer salts insensitive to flow variations more expensive than RI detector not usable with mobile phase buffers. 

Th EL 0 detects any compound less volatile thon the mobile phase to low nanogrom levels using a simple 3-Slep process  

Column effluent passes through o needle and mixes with nitrogen gas to form o dispersion of droplets. 

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