Quantitative analysis of chlorofluorocarbons

Vidal-Madjar, Claire; Parey, Fatima; Excoffier, Jean-Louis; Békássy, Sándor

doi:10.1016/s0021-9673(00)80298-8

Cited by 15 publications

(4 citation statements)

References 28 publications

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“…The HFC mass detection limits are considerably higher, 14 and 45 ng for HFC-125 and -134a, respectively. These results are worse than those of Vidal-Madjar et al 40 Their ECD mass detection limits for CFC-11 are 75 fg in pulsed detector mode, 250 ft in dc mode, corrected for a SNR of 3. A mass detection limit for CFC-12 of 1.6 pg for dc detector mode is estimated based on their data.…”

Section: Discussioncontrasting

confidence: 67%

Temperature-Dependent Electron Capture Detector Response to Common Alternative Fluorocarbons

Sousa

Bialkowski

1997

Anal. Chem.

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The relative electron capture detector (ECD) response to alternative fluorocarbons (AFCs) using gas chromatography are found to be at least 1 order of magnitude lower than that for CFC-12. Detection limits for the chlorofluorocarbons CFC-12, HCFC-22, HCFC-123, and HCFC-124 are found to be 2.5, 90, 30, and 90 pg, respectively. Those for the hydrofluorocarbons are significantly poorer; 14 and 45 ng for HFC-125 and HFC-134a, respectively. HFC-152a was not detected using ECD. Since atmospheric concentrations of these compounds are in the low part-per-trillion level, GC-ECD is apparently not sensitive enough to be used for AFC analysis without substantial preconcentration. Two columns are evaluated for the AFC separation. The Poraplot Q WPLOT column showed good separation ability, though column bleed limits detection performance. A Carboxen 1004 packed column exhibits much lower interference. But separations are time consuming and peak broadening adversely affects limits of detection. Mechanisms for the ECD response are proposed based on thermodynamics and temperature-dependent ECD responses. CFC-12, HCFC-123, and HFC-125 apparently undergo ion-forming dissociative electron capture. The electron capture process for HCFC-22 and HFC-134a appear to form molecular ions. Both mechanisms appear to be operative for HCFC-124 electron capture. Dissociative electron capture rate constants for HCFC-123, HCFC-124, and HFC-125 are estimated to be 3.5 × 10(-)(10), 1.0 × 10(-)(10), and 5.6 × 10(-)(13) cm(3) s(-)(1), respectively at 300 °C.

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Section: Discussioncontrasting

confidence: 67%

Temperature-Dependent Electron Capture Detector Response to Common Alternative Fluorocarbons

Sousa

Bialkowski

1997

Anal. Chem.

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“…Such results are in contrast, however, with some welldocumented examples of hypercoulometric response (4)(5)(6)(7), observed for different strong electrophores in a pulsed e.c.d. and with the fact that some halocarbons (possibly the many compounds following mechanism ß in the classification of Wentworth and Chen) are especially likely to give nonlinear 1 Present address: Istituto sull' Inquinamento Atmosférico del C.N.R., Area della Ricerca di Roma, C.P.…”

contrasting

confidence: 85%

Experimental parameters affecting hypercoulometric response in gas-phase coulometry

Ciccioli¹,

Hayes²

1985

Anal. Chem.

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The response of an electron-capture detector designed for coulometric response was examined as a function of solute, pulse interval, carrier-gas type, solute amount, carrier-gas flow rate, and chromatographic-peak profile. For CCl3F, it was shown that the average numbers of electrons absorbed per molecule ranged from 1.0 to 4.1, varying primarily with pulse interval but also displaying a complex dependence on sample amount. Comparison of these results with theoretical expectations leads to the conclusion that a 1:1 "coulometric response" may not be observed under certain operating conditions. Because the specific conditions required depend on many variables, including, to some extent, sample amount, true coulometric operation of an electron-capture detector is difficult to establish and maintain. Effects which may contribute to the production of hypercoulometric response are critically discussed.

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“…Such measurements are useful to determine the rates of rapid processes associated with heterogeneous electron transfer (3-8). In a previous paper, we demonstrated that the scan rate employed in the cyclic voltammetry technique could be extended to values as high as 500 kV s_1 (9). These voltammograms were, however, distorted by the combined effects of ohmic drop, cell time constant, and instrument response.…”

Section: Resultsmentioning

confidence: 99%

“…Vejrosta and Novak (7) described a dynamic system for producing parts-per-billion levels of such compounds by two-stage dilution of a pure gas stream saturated with the compound of interest. Other workers reported the use of permeation tubes with gravimetricaly calibrated permeation rates to produce accurate concentrations of single organic species (8,9).…”

mentioning

confidence: 99%

Preparation of accurate multicomponent gas standards of volatile toxic organic compounds in the low-parts-per-billion range

Rhoderick¹,

Zielinski²

1988

Anal. Chem.

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Quantitative analysis of chlorofluorocarbons

Cited by 15 publications

References 28 publications

Temperature-Dependent Electron Capture Detector Response to Common Alternative Fluorocarbons

Temperature-Dependent Electron Capture Detector Response to Common Alternative Fluorocarbons

Experimental parameters affecting hypercoulometric response in gas-phase coulometry

Preparation of accurate multicomponent gas standards of volatile toxic organic compounds in the low-parts-per-billion range

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