Argon ionization

Fales and Pisano (30) were the first to describe the gas chromatographic analysis of amphetamine. They used 4% SE-30 in a silanized glass column and an argon ionization detector for the separation of (3-phenethylamine, amphetamine, norephedrine, eph drine, histamine, tyramine, dimethyltriptamine, tryptamine, 5-methoxytryptamine, benzylamine, N-methylbenzylamine, octopamine, synephrine, normetanephrine, serotonin, N-acetyltryptamine, find melatonin. The method was also used for the analysis of amphetamine extracted from urine. 

James and Martin soon developed a gas-density balance as a detector, but the sensitivity of GLC was increased enormously when the argon ionization detector was invented by James Lovelock it was he who also produced the electron capture detector in conjunction with S. R. Lipsky in 1959.162 The flame ionization detector originated in the same year.163 Another important advance in the early days of GLC was the introduction of capillary columns, which were first used by M. J. E. Golay in 1956.164165 The development of some of the first commercial instrumentation has been described.166167... 

The sensitivity of the detector was similar to that of the katherometer i.e. about 1 x 10 g/ml. Unfortunately, the practical lifetime of this detector was also relatively short as it was eclipsed by both the FID and the argon ionization family of detectors introduced by Lovelock. Nevertheless, the development of these early detectors not only helped establish GC as a viable analytical technique but also stimulated the development of other types of vapor sensing devices. The future... 

The equation indicates (and experiments confirm) that the rapid increase in current flow with increasing vapor concentration will, in theory, lead to an infinite current at some finite vapor concentration. This would appear to render the argon ionization system impractical as a GC detector. It will be seen however that this cascade effect can be controlled by suitable electronic circuitry. 

The type of detector to be employed determines the nature of the carrier gas which may be used. Argon is used with the argon ionization detector. Helium is used with flame-ionization, thermal conductivity, thermionic emission, and cross-section detectors. Hydrogen may be used in thermal conductivity detectors to give maximum sensitivity. Probably the commonest and cheapest carrier gas is nitrogen, which can be used with flame-ionization, electron capture, thermal conductivity, and cross-section detectors. Argon-methane mixtures may be used with electron capture detectors. 

Apparatus Barber-Colman Model 10 or an E.I.R. instrument fitted with argon ionization detector. 

Fia. 15. Separation of tryptamine-related indole bases. The compounds are N,N-dimethyltiyptamine (DMT), eneamine (acetone condensation product) from tiypt-amine (TRYPT-SB), 7-trimethylsilyloxy-JV,iV-dimethyltryptamine (7-OH-DMT-TMSi), 4-trimethylsilyloxy-iV,i r-dimethyltryptaniine (4-OH-DMT-TMSi), 5-tri-methylsilyloxy-iV,JV-dimethyltryptamine (5-OH-DMT-TMSi), 6-trimethylsUyloxy-JV, iV -dimethyltryptamine (6-OH-DMT-TMSi), and the eneamine (acetone condensation product) from 5-trimethylsilyloxytryptamine (5-OH-TRYPT-TMSi-SB). Conditions 7% F-60, 1% EGSS-Z, on 100-120-mesh Gas Chrom P, 182 C, 18 psi argon ionization detection system. Reproduced from Homing et al. (H15), with permission. 

Apparatm Barber-Colman Model 10 gas chromatograph equipped with an Argon ionization detector (A-4183). 

The purpose of the detector is to determine when and how much of a compound has emerged from the column. Although the goal of all detectors is to be as sensitive as possible, many detectors are designed to be selective for certain classes of compounds. Dozens of different types of detectors have been developed, but only a few are used routinely. Those are thermal conductivity (TC), thermionic (N/P), electron capture (ECD), flame photometric (FPD), Hall electroconductivity detector (Hall or ELCD), hydrogen flame ionization detector (FID), argon ionization (AI), photoionization (PID), gas density balance (GDB), and the mass spectrometer. Chemists usually select a detector by the following criteria, listed in priority ... 

Argon ionization All organic substances with Very good 0.1-100 ng, Good Very sensitive to impurities and water ... 

Detectors are either concentration sensitive or mass flow sensitive. The signal from a concentration-sensitive detector is related to the concentration of the solute in the detector and is decreased by dilution with a makeup gas. The sample is usually not destroyed. Thermal conductivity, argon-ionization, and electron capture detectors are concentration sensitive. In mass-flow-sensitive detectors, the signal is related to the rate at which solute molecules enter the detector and is not affected by the makeup gas. These detectors usually destroy the sample, such as flame ionization and flame thermionic detectors. Sometimes two-column GC is used to increase resolution, by taking cuts of eluents from an initial column and directing them to a second column for secondary separation. The first detector must be nondestructive or else the eludnt split prior to detection, with a portion going to the second column. 

Thermal conductivity detectors have been discussed in detail by Ingraham (107), who also described their application to thermodynamic and kinetic measurements. In this same book. Lodding (4) describes the gas density detector as well as several ionization detectors, such as the argon ionization detector, the electron capture detector, and others. Flame ionization detectors have been described in detail by Brody and Chaney (108) and Johnson (109). The latter also discusses other types of detectors. Malone and McFad-den (110) described many different types of special identification detectors, such as those listed in Table 8.3. Numerous texts on gas chromatography describe a wide variety of detectors, many of them useful in EGD and EGA. 

Scentoscreen (Gas Chromatograph) with Argon Ionization Detector... 

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