Argon detector

The electron capture detector is the result of a series of developments which were initiated in 1951 by D. J. Pompeo and J. W. Otvos (14) of the Shell Company s development laboratory in California. The device they invented was a beta-ray ionization cross-section detector (Section 5.8). Deal et al. (15) at the Shell laboratory in California and Boer (16) in Amsterdam modified the detector, used originally to monitor effluents of a large scale plant process, for applications in GC. From the limited success of the detector. Lovelock (17) produced the beta-ray argon detector in 1958 (Section 5.8). This modification substituted argon as the carrier gas and placed a potential of 1000 V across the electrodes. Argon passing between the electrodes absorbed radiation and formed a metastable species with energy (11.6 eV) sufficient to ionize most substances. Proposed mechanisms for this process are ... 

QUANTITATIVE ASPECTS. Normally the presence of high quantities of the organic acid is sufficient for diagnosis. However, quantification is sometimes required. To do this, serial amounts of the individual acid must be carried through the derivatization, and a calibration curve set up. The various acids show widely different responses to the argon detector. From the standard curves the amounts can be derived by interpolation. Calculation on the basis of urine dilution must be included as well as the aliquot of the final solution that was taken for injection. The procedure for this is similar to that described for estriol in pregnancy urine. 

Hill, D. W., Newell, H. A. The effect of nitrous oxide and carbon dioxide on the sensitivity of small argon detector for use in gas chromatography. Nature 201, 1215 (1964). 

In retrospect the triad of symposia held in 1956, 1958 and 1960 not only established GC as a unique and reliable analytical technique but also contained the first disclosure of 90% of the devices used in modern GC. Between the 1958 and 1960 symposia. Lovelock developed a family of ionization detectors starting with the Argon Detector [16,17] in 1958 of which three different models were created and demonstrated to function well, and ending in 1959 with the electron capture detector [18], which, second to the FID, is probably the most commonly used detector today. 

At the 1960 symposium, research into the mechanism of detection of a number of the more important GC detectors was reported. The FID was carefully examined by Ongkiehong [19] and Desty et al. [20], the different argon detectors were described in detail by Lovelock [21] and the performance of the FID and Argon Detectors were compared by Condon et al. [22]. The integral and differential ionization detectors were also discussed by Matousek [23]. At the end of the 1960 symposium, the majority of the GC detectors that are used today had been described and their function explained and understood. Since that time few, if any, new GC detectors have been introduced and innovations that have been described have been largely extensions and improvements of older concepts. 

Argon Detectors, Helium Detectors and the Electron Capture Detector... 

Power Supply Circuit to the Macro Argon Detector... 

Although the argon detector is a very sensitive detector and can achieve ionization efficiencies of greater than 0.5%, the detector was not popular, largely because it was not linear over more than two orders of magnitude of concentration (0.98 < r > 1.02) and its... 

A diagram of the micro argon detector sensor is shown in figure 3. This sensor was designed to have a very small "effective" volume so that it could be used with capillary columns where the flow rate may be as low as 0.1 ml/min or less. In the micro argon detector sensor, the anode is withdrawn into a small cavity about 2.5 mm in diameter. 

The Separation of a Hydrocarbon Mxtnre on a Nylon Capillary Column Using the Micro Argon Detector... 

The triode detector is a modification of the micro argon detector and a diagram of the triode detector sensor is shown in figure 5. 

Table 1 The Relative Characteristics of the Three Different Argon Detectors...

In operation the cathode is connected to earth, the collector gives a positive signal to the amplifier and the anode is connected to the positive power supply. The specifications of all three argon detectors are given in Table 1. 

The Separation of a Mixture of Hydrocarbons Monitored by the Thermal Argon Detector and the FID... 

It is seen that the performance of the two detectors is very similar. The thermal argon detector is not, presently, commercially available. However, its high sensitivity, freedom from radioactivity and electron producing ancillaries make it a very simple detector to fabricate and... 

The development of the ionization detectors by Lovelock that evolved from the original argon detector culminated in the invention of the electron capture detector [2]. However, the electron capture detector operates on a different principle from that of the argon detector. A low energy 3-ray source is used in the sensor to produce electrons and ions. The first source to be used was tritium absorbed into a silver foil but, due to its relative instability at high temperatures, this was quickly replaced by the far more thermally stable Ni source. 

The lamp was operated at about 3 mm of mercury pressure with a current of 1.5 mA. under which conditions the potential across the electrodes was 220 V. Pitkethly reported that a concentration of lO g/1 gave an electrode voltage change of 0.3 V. Now the noise level was reported as about 10 mV thus at a signal-to-noise level of 2 the minimum detectable concentration would be about 3 x lO ig/ml. This sensitivity is comparable to that of the FID and the argon detector. 

The Simple or Macro Argon Detector Sensor The Micro Argon Detector The Triode Detector The Thermal Argon Detector The Helium Detector The Pulsed Helium Discharge Detector The Electron Capture Detector The Pulsed Discharge Electron Capture Detector References Chapter 7... 

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