Page 133 - Basic Gas Chromatography
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119   1   TCD                                 These          b   RMR’   ~   7   ~   51   85   "   Ay   jo   ee   *   Fe   oe   Presto

          list.                               to Lovelock,   provides   that   consequently,            of
          following                           attributed   detector   electrons.   and,   Selected      permission



          the   sensitivity.   Characteristics    “capture   analysis.   for  Values                    by    100.
          in                                    selective   like pesticides                             Science   =
          given                          (ECD)   generally   a   that   residue   Response   .  Conductivity”   oe   R   9.9   benzene

          is   moderate   (TCD)               is   GC)   is   It   compounds   materials   TCD   Gases   12.5   12.7   100.0   128.0   18.0   Samples   17.5   13.5   ie   .!   10.1   12.7   6.0   4.6   Chromatographic   Inc.   Standard:

    (ECD)   characteristics   with  detector   Detector   ppm)   compounds   DETECTOR   (for   [23].   1961   those   pesticide   in   and   Thermal   Carrier   of  Journal   Industries,   helium.


    Detector   TCD   Conductivity   (~10   gas—helium   limit—400°C   CAPTURE   ECD   the   in  publication   for   halogenated   is   uses   Conductivities   the   Preston   of   100.   in  response



    Capture   of  summary   universal   MDQ—10°°g   Response—ail   Linearity—10*   Stability—good   Carrier   Temperature   of  invention   his   sensitivity   include   primary   Thermal   [20]*   dioxide   iodide   from  Reproduced   Division   A   =   He   to   molar


    Electron   A   rugged,   a   is   Thermal   aN  OF  HS  .   ELECTRON   The   on   based   high   very   compounds   its   of   one   7.4  TABLE   Compounds   Compound   Argon   Carbon   Helium   Hydrogen   Nitrogen   Ethane   n-Butane  n-Nonane   i-Butane   Cyclohexane   Benzene   Acetone   Ethanol   Chloroform   Methyl   acetate   Ethyl   *   Publications,   Relative   *   Relative   »
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   Detectors   so-called   integrator,   or   conductivity   returns   greater   the   high   small   causing   leaks   constant   constant   setting   a   depend-   temperature   circuit   larger   a   noise   for   TCD   columns   become   several   some   are   nL   a   manufacturer   gas   two   cell   at   conductivity   most   TC   that   7.4   values.   peak   The   as   the   for   with   quantitative


          (the   bridge   the   However,   because   ultimately   from   free   or   maintain   specify   (AT),   simpler   provides   less   and   desirable   Typically,   packed   not   and   in   columns   etching   the   the   the   so   highest   Table   TC   unusual   [21].   helium   values   directly

         divider   recorder,   the  thermal   the   and   filaments,   sensitivity.   life   wires,   must   be   voltage   to   may   difference   filament   unlike   the   limits,   is  volume   sensitivity.   for   has   20   to   uL   be  obtained   capillary   made   by   Another   operation   through   thermal   analyzed,   have   the   listed   in   smaller   to   get   inversion   using   response   correlate   for


         voltage   a   to   eluted,   value   the   filament   system   constant   used   controls   the   Nulling   detection   cell   good   very   capillaries   down   can   when   been   its   in   alternately   a   have   to   be   which   values   much   expect   peak   hydrogen   relative   not   necessary



         a   fed   former   to   the   shorter   tungsten   GC   at   can   be   temperature   Controlling   Bridge,   unbalance.   small   greater   are   narrow   required   has   instrument.   TCD;   must   hydrogen   have   can   partial   does   are
         across   is   it   of   fully   is   its   applied   greater   in   the   the   carrier gas.   operated   circuit   detector   a   the   lower   a   and   which   with   volumes   chromatograms   small   cell   passed   [5].   TCD   samples   relative   solids   one   to   due   analyze   experimental   response   factors

         dropped   part   or   analyte   returns   to   current   the   and   result   oxidize   reason,   be   can   the   or   control.   of   to  nulling   the  bridge   amplification,   chapter,   shapes   wL   140   Their   use   with   good   is  usually   micro-GC   single-cell   are   second   the   from   the   and  helium   from   the   liquids   and   gas,   W   a   attempts   to   some   TCD   calibration   FID.



         is   all   After   the   heating   also   readily   this   oxygen-free   Bridge   elaborate   Thus,   temperature,   type   amounts   this   in   of  peak   around   available   that   gas   extremely   a   for   uL)   (5   reference)   per   with   different   are   seen   as   carrier   a   shape   of   one   Although   the   for   the
         voltage   then   system.   cavities   the   differential   temperatures   oxygen   For   out.   with   more   temperature.   a   particular   measures   greater   earlier   capillaries.   are   shown   Make-up   An   chip   volume   and   times   10   used   gas   gases   be   can   well   as   used   as   the   if   contains   obvious   as


         That   and   data   sample   larger   of   burn   operated   Wheatstone   but   a   a  voltage,   the   it  constant   directly   range,   noted   reproduction   volumes   bore   but   cells   have   19].   TCDs.   a silica   on   small   (sample   of   carrier   very   is   used   It   [20].   gases   is   often   in   occurs   [22].   also   7.4   listed.   is   it   the   same

         bridge.   attenuator)   the   balance.   The   temperature   filament   impurities   to   The   current,   filament   current,   on   keep   have   wide   [18,   with   a   frequency   that   commonly   other   nitrogen   effect   gas   Table   samples   values,
   116       other   in   to   them   and   ing   to   which   linear   [17].   As   faithful   cells   or   routine,   Studies   cases   used   volume   uses   streams   a   The   (TC)   values   all   If   shapes,   same   carrier   the   TC   analysis,
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