José Antonio García-Domínguez

Contribution to the study of micropacked columns in gas chromatography

Abstract Several chromatographic columns made from glass tubes of I.D. 0.5–1 mm and with solid support particle sizes of 100–120 and 120–140 mesh were evaluated. The effect of liquid film thickness, column diameter, permeability and particle diameter to column diameter ratio on column efficiency is discussed. The pressure drop at the optimum gas velocity per unit column length and per theoretical plate is considered. A column is discussed with 6250 theoretical plates per metre, and others, les efficient per unit length, with a total of about 60 000 theoretical plates which can be run at about 7 kg/cm 2 if nitrogen is used.

The hold-up time in gas chromatography1: III. Linearity of the plot of ln tR′ of the n-alkanes vs. carbon number questioned

Abstract Three arguments are presented to show that the plot of the logarithms of the adjusted retention times of n -alkanes eluted under isothermal conditions versus their chain length is not a straight line, as generally accepted, even for n -alkanes of seventeen carbon atoms. Comparison of values of t R ′ deduced by methods based on the linearity assumption (ln t R ′= mz + n ) and on a different approach [ t R = A +exp( B + Cz D )] shows that experimental retention times do not fit the first expression, independently of the value used for the hold-up time, even if the correlation coefficient of the fit is better than 0.99999.

Measuring specific retention volumes in capillary gas chromatography with improved accuracy and precision

Abstract The specific retention volume (Vg), which has traditionally been determined in gas chromatography using long, heavily loaded packed columns, should produce better, more reliable values if capillary columns are used. However, the smaller dimensions of some of the parameters involved introduces additional sources of error which have been overcome with a recently proposed equation. A careful consideration of the sources of error involved has been carried out using both the traditional and the new equations. The conclusion drawn is that the new equation will produce reliable Vg values with expected errors (1%) lower than those expected from packed columns (2%) using the traditional equation.

Method for the classification and selection of stationary phases in gas chromatography

Abstract A new method of classification is applied to 233 stationary phases used in gas chromatography. Clustering together all those which have similar chromatographic behaviour, 45 are found to be singular in the sense that no other stationary phase exhibits similar characteristics and therefore they may not be replaced by any other. The remaining 188 stationary phases may be reduced to 33 selected liquids which may represent the larger set of 188, in the sense that all selectivity possibilities of the 188 stationary phases are retained in the 33 selected. A further reduction in the number of selected stationary phases will adversely affect the separation capacity of the set. The selected list of 33 stationary phases is not unique, and many of them may be replaced by an equivalent one without any loss in separation capacity.

Reduction of the number of characterizing probes in gas chromatography by factor analysis

Determination du comportement chromatographique des phases stationnaires, a partir de 10 solutes types

Indirect determination of specific retention volumes in gas chromatography use of the retention indices of McReynolds' samples

Abstract The specific retention volumes of n -decane on 24 liquid stationary phases of the silicone type were calculated from the retention indices of the samples used by McReynolds in his characterization of gas chromatographic stationary phases. The average error of prediction was 2.24%. The effects of errors on the logarithm of the relative retentions of consecutive n -alkanes and the values of the retention indices were studied, and also its dependence on stationary phase polarity.

Indirect determination of specific retention volumes in gas chromatography : Use of retentions of the McReynolds probes relative to n-decane

Abstract Specific retention volumes of n -decane oon 24 liquid stationary phases of the silicone type have been calculated from retention data relative to n -decane, of n -dodecane and the ten probes used by McReynolds to characterize stationary phases in gas chromatography. The average error of predictionis 1.2%, with only one error above 3% (5%). Relative retentions of consecutive n -alkanes varied from 1.18 to 1.64. The experimental values of the specific retention volumes of n -decane varied between 1.39 and 129.2 ml/g.

Slow gas-phase oxidation of ethylal with C-14 as a tracer

The slow gas-phase oxidation of ethylal was investigated at low temperatures (160–190°C) by the static method. The main products were carbon oxides, water, acetaldehyde, acetic acid, ethanol and ethyl formate with some methanol, formaldehyde, formic acid, n-butane, ethylene and peroxides. Three different ethylal samples labelled with C-14 in each one of its three different positions, respectively, have been synthesized; their oxidation has been studied and the reaction products analysed by radiochromatography. A mechanism is suggested where the branching intermediates are hydroperoxides derived from ethylal.