Flow scheme for GC reprised
 Flow scheme for High Performance Liquid Chromatograph
                                      4) Sample mix is separated on 
 1) Solvents                          short ~10”  packed column
 selected by 
 quaternary                             5) Separated components 
 Mixing valve (A)                       detected at detector
                                       Packed column
                       HPLC pump                      Detector (D) 
   Quaternary flow mixing    HPLC injector port 
   solenoid valve  (B)       (sample in here too)
                                                   6) Exiting mixture 
     2) High pressure HPLC pump sucks selected     is discarded here
     solvents into and through injector port (C) 
     3) Sample mix is injected into port and combined with solvents
  GC 
  chromatogram
  HPLC
  chromatogram
            GC      vs.        HPLC
  1. Thermal ramp              1. Solvent mixing/25 oC 
  2. Gas mobile phase (He)     2. Liquid mobile phase 
                                  (solvents)
  3. Flow produced by gas      3. Flow produced by pump
     pressure
  4.  Flow is often split      4.  Flow is not split
  5. Separated species often   5. Separated species can 
     lost during detection        often be recovered 
  6. Chemical apps common      6. Biological apps common
  7. 10-20 m capillary         7. 0.25 m packed columns 
     columns (long)               (short)
  Single piston 
  HPLC pump
                   Must achieve maximum of 60-
     $3000-6000    120 MPa pressures without 
                   leaking or seal failure  (600-
                   1200 atm=9000-18,000 psi)