Precision of an automated all-glass capillary gas chromatography system with an electron capture detector for the trace analysis of estrogens

Subnanogram detection of steroids has become increasingly important today. One applicable method for gas chromatographic determination of subnanogram quantities of estrogens as halogenated derivatives is electron capture detection. HFB-derivatives of 7 different estrogens were automatically injected onto a prolonged narrow bore wall-coated glass capillary column. Normal split injection could not be used for this trace analysis because of too much loss of sample. Only small amounts of sample were available from which double analysis had to be performed. Cross-contamination of the automatic sampling system as well as precision of retention times and peak areas were determined. The type of injection described showed better quantitative results compared to the splitless injection technique. All details of the system used together with the results are this discussed in this paper.     

Gas-liquid chromatography of amino acids: Columns and methodology as a basis for routine amino acid analysis using glass capillary gas chromatography

A carefully Standardized technique is described for the preparation of glass capillary columns which can be used successfully for routine quantitative amino acid analysis. Comparison is made between two different modes of sample injection. Preliminary quantitative results from “split” injection and “on-column” injection techniques are evaluated statistically and it is concluded that the “on-column” system is a prerequisite for quantitative amino acid analysis by glass capillary gas chromatography. An analysis of fish muscle protein hydrolyzate illustrates an application of this technique and results are compared with those from a packed column analysis.     

Comparison of dynamically coated SE-54, SP-2250 and carbowax 20M wall-coated open tubular (WCOT) glass capillary columns,prepared after surface pretreatment with Superox™-4 or with BaCO3

A new surface pretreatment for the preparation of wall-coated open tubular (WCOT) glass capillary columns has been evaluated. This technique involves the application of a non-extractable layer of Superox?-4, a 4,000,000 MW polyethylene glycol, to the glass surface as a pretreatment and deactivation agent. Unlike other polyethylene glycols, Superox-4 is stable at high temperatures (> 300°C) in the absence of oxygen, coats smoothly onto a bare glass surface and resists droplet formation. WCOT columns (SE-54, Carbowax 20M, and SP-2250) prepared using this technique are compared to columns prepared using a modified Grob [2,3] BaCO₃ procedure. The Superox-4 pretreated columns were equal or superior in quality to the BaCO₃ pretreated columns, based on the appearance of an activity standard and the effective theoretical plates (N_eff) per meter. Chromatograms showing practical application of the WCOT columns prepared using both methods is given.     

Characteristics and performance of gas chromatographic detectors with glass capillary columns

A comparison of the characteristics and Performance of the flame ionization, electron capture, and flame photometric detectors with capillary columns is described. Factors which may affect the limits of detection, linearity, chromatographic peak shape, and other detector performance characteristics are discussed and compared with the results of a model derived for the behavior of concentration and mass flow-rate dependent chromatographic detectors used with capillary GC systems. Examples are given of highly complex and labile mixtures such as pesticide residues and products from coal hydrogenation.     

Are we using the full resolving power of capillary GC?

Precise evaluation of the chromatographic data by means of the relative retention will allow the full use of the resolution achieved by capillary columns. In practice, retention-index determination is best suited for this purpose. The reproducibility of retention-index determination strongly depends, among other factors, on the accuracy of retention time measurement. A reproducibility of ±0,05 i.u. can be easily achieved with modern gas chromatographic equipment, provided the retention times can be measured with an accuracy of at least ±0.01%. This can be shown by error propagation analysis of retention-index calculation performed with the aid of a programmable pocket calculator.     

The theoretical basis of column chromatography in multicomponent separations. Part 1: Analytical requirements and peak resolution. Development of a high performance column system

The point of our published papers since 1957 is reviewed. The relations between the required value of peak resolution, K₁ (or R), and peak separation, K₃ (eqn 9); K₁ and relative accuracy of a peak height quantitative method, P_h (eqn. 10); K₁ and relative accuracy of a peak area method, P_a, (eqn. 12) at different concentration ratios, ?, are derived. The final result in Table 2 shows a large influence of ? on the required value of K₁. The approximately linear relation between peak width and retention value (eqn. 18) exists not only in GC. but also in HPLC. Plate height values H¹ and H^∞ for a solute with capacity ratio, k′, equal to unity or approaching infinity, respectively, are used to evaluate the column efficiency (eqn. 20). The measuring methods (eqn. 21,22,23) and parameters effecting on H¹ and H^∞ are given for GC packed column (eqn. 24), GC open tubular column (eqn. 25) and HPLC (eqn. 26). In the light of this, columns of high efficiency were developed. Some typical chromatograms for high speed analysis and separation of complex mixtures are given.