Gas Chromatography Detectors - Ionization Detectors > The Micro Argon Detector > Page 60

At the other end of the sensor is another inlet that provides a scavenger flow of argon that rapidly removes the solute from the cell through two holes at the bottom of the anode cavity. This procedure reduces the effective sensor volume to less than a microliter and thus allows the efficient use of a capillary column. The radioactive source originally used was about 25 micro-curies of radium (an a particle source). Although the radioactive source was very small (defined in those days as about a "wrist watch", as equivalent quantities of radium were used to produce the luminous dials of many watches at that time) it was subsequently recognized that exposure to a particles could cause a health problem. Eventually radium was replaced by tritium (a very weak b ray emitter) which, although a fairly strong source (sometimes as much as one curie was used), it was relatively harmless from the point of view of radiation energy. However, it is also somewhat unstable at high temperatures causing loss of tritium to the air and consequent atmospheric contamination.

Column: 1000 ft of Nylon tubing 0.020 in I.D. Temperature 23oC. Column efficiency for butane eluted at 65 minutes 0.75 x 106 theoretical plates

Figure 30 The Separation of a Hydrocarbon Mixture on a Nylon Capillary Column Using the Micro Argon Detector