A non‐mechanical chemical concentration modulator for multiplex gas chromatography

Abstract

Figure I Chromatogram resulting from a slngle 6 watt current pulse applied for 0.6 second. --J. R. Valentin and G. C. Carfe Mail Stop 239-12,

Multiplex gas chromatography by thermal modulation of a fused silica capillary column

“…The positive and negative parts are generated by different mechanisms and so differ in their amplitudes and band lengths. A convenient measure of this difference, or signal asymmetery, is the ratio of the sizes of the two parts from eq 8 and 9, (C+ -C)/(C-C_) = k + 1 (11) Expected and measured asymmetry ratios are given in Table I. Equations 8-11 predict large positive part signal amplitudes and very asymmetrical signal forms for strongly retained substances.…”

“…Wells has more recently demonstrated a similar technique using a fast valve to compress and chop the sample stream at the detector (9). We have demonstrated photochemical (10), thermal desorption (11), thermal decomposition (12), and oxidative (13) modulators for gas chromatography and thermal desorption (14) and electrochemical (15) modulators for liquid chromatography. Of course, injection ports, automated valves, and other sampling devices of conventional chromatography also fit the definition of modulators.…”

Concentration modulation by thermal decomposition for multiplex gas chromatography

“…The study was conducted with a Carle AGC Model 111 gas chromatograph equipped with a thermistor bead detector and an external sample modulator system reported previously [6]. The system reported here differs from the previous one in that a 0.25 mm ID by 0.38 mm OD by 21.6 cm long uncoated 304 stainless steel capillary tube was used as the modulator.…”

“…The chromatogram is then recovered by computational deconvolution of the resulting signal 111. Several types of devices have been constructed which modulate the sample stream producing multiple concentration pulses [2,3,4,5,6]. These devices modulate most or all components of the sample.…”

Electrochemical modulator for liquid chromatography

“…This chemistry is also an opportunity to apply them in ways not possible with simple mechanical valves. Several examples of chemical modulators have been described for gas chromatography (2)(3)(4)(5)(6), but only two have been used for liquid chromatography (7,8). Smit (9,10) described the use of valves as modulators in liquid chromatography.…”