Anion chromatography in open tubular capillary columns with indirect fluorometric detection

Summary A C₈ reversed-phase open tubular capillary column is dynamically modified with cetylpyridinium chloride to provide anion-exchange sites. Sodium salicylate is used as the eluent at the micromolar concentration range. The low capacity of the dynamically modified column allows the elution of common anions with k′ values similar to those in conventional ion chromatography. The reduced salicylate concentration allows good detectability in the indirect fluorescence mode, even though the baseline noise increased because the fluorescence intensity is lower. The noise level is equivalent to one picogram of non-fluorescing anions.     

Chemically modified teflon wall-coated open tubular columns for gas chromatography

Summary Wall-coated open tubular columns prepared from chemically modified teflon tubing have been developed for gas chromatography. Chemical reaction of the inner walls of teflon tubing allows bonding of an adhesive layer on which a variety of stationary phaes can be coated. Test mixtures of alkanes and alcohols were used to investigate the chromatographic properties of these columns and the stability and mixing of the adhesive and stationary phae layers. the results in dicate that mixing of the layers is negligible and that the column is stable for a long period of time.Principle author     

The application of porous silica layers in open tubular columns for liquid chromatography

Summary Two methods to realize a porous retentive silica layer on the inner wall of 10–25 μm fused silica capillaries for OTLC, etching and precipitation of silica from solution, have been investigated. Etching of the fused silica capillaries with 1M KOH, creates an activated surface, but the capacity of the silica layer is too small to serve as retentive layer in OTLC. Better prospects are offered by the precipitation of silica from a solution of polyethoxysiloxane, dynamically coated on the inner wall of the fused silica capillary. It appears to be possible to deposite a porous silica layer up to 0.8 μm thick (in a 25 μm capillary) by this method, which seems to be suitable for liquid-solid an dynamically generated liquid-liquid chromatography in open tubular columns. The performance of these columns are demonstrated by means of efficient separations of test mixtures using on-column fluorescence detection.     

Ultimate resolution in open tubular columns

The expression for the resolution function, R, in terms of operating parameters for open tubular columns has been extended to include inlet contributions to the peak variance. Subsequent optimization has revealed the existence of optima in the column radius, the stationary phase thickness and the diffusion coefficient ratio in the stationary and mobile phases-in addition to the well-known optimum in the flow velocity. This implies that R at optimum becomes R=f(K)L^0.6V_i^?0.2, i.e. a function only of the column length, L, the inlet volume, V_i, and the concentration distribution coefficient, K. For given K, L and V_i all other parameters such as retention time and pressure drop can thus be directly computed. The information is finally consolidated in the form of contour diagrams. The text itself is cast in the form of a science fantasy.     

Fast separations with open tubular ion exchange capillary columns

Fused silica columns of 4.6 μm i.d. were coated with 3-sulfopropylsilane as a cation exchanger and 3-(2-aminoethyl-amino)-propylsilane as an anion exchanger. Fast separations of cations (< 25 seconds) and of anions (< 35 seconds) were obtained, using a potentiometric microelectrode as a detector. In proceeding towards smaller i.d.s, a mixture of alkali metal cations could be separated successfully in an uncoated fused silica capillary of 2.3 μm i.d. as a result of retention by the surface silanol groups at pH 9.4.     

Pyrolysis-gas chromatography with linearly programmed temperature packed and open tubular columns. The thermal degradation of polyolefins

Summary The use of linearly programmed temperature packed and open tubular (Golay) columns was introduced in pyrolysis-gas Chromatographic systems. The use of packed columns was illustrated with various polymers.The thermal breakdown of polyolefins was studied more thoroughly employing programmed temperature open tubular (Golay) columns. Possibilities for the interpretation of the chromatograms were illustrated.

---

Zusammenfassung Die Anwendung von gepackten Säulen und Capillarsäulen in Verbindung mit linearer Temperaturprogrammierung wurde in die Pyrolyse Gaschromatographie eingeführt.Temperaturprogrammierte gepackte Säulen wurden zur Pyrolyse verschiedener Polymere verwendet. Der thermische Abbau olefinischer Polymere wurde mit temperaturprogrammierten Capillarsäulen eingehender studiert. Möglichkeiten zur Interpretation der Chromatogramme wurden aufgezeigt.

---

---

Dedicated to Prof. Dr. Karl Ziegler on the occasion of his Nobel-Price.     

Pyrolysis-gas chromatography with linearly programmed temperature packed and open tubular columns. the thermal degradation of polyolefins

Summary The advantages of the use of programmed temperature open tubular columns for the separation of the pyrolysis products of polymers is again demonstrated, using polyethylene samples. It is also shown that the combination of pyrolysis-gas chromatography with subsequent hydrogenation of the thermal breakdown products using open tubular columns for separation can successfully be used in the identification of the unsaturated components formed during pyrolysis.Based on the obtained results, the schematic of the thermal breakdown mechanism of polyethylene could be established.It is further proved that the investigation of the Chromatographic pyrolysis pattern permits an evaluation regarding the degree of branching in the original polyethylene molecules.

---

Zusammenfassung Die Anwendung von linear-temperaturprogrammierten Capillarsäulen zur Auftrennung von Pyrolyseprodukten wird am Beispiel der Pyrolyse von verschiedenen Polyäthylenproben beschrieben. Es wird ferner gezeigt, da\ die Methode der hydrierenden Pyrolyse-Gaschromatographie ebenfalls in Verbindung mit Capillarsäulen mÖglich ist und zur Identifizierung von bei der Pyrolyse entstandenen ungesättigten Verbindungen verwendet werden kann.Auf Grund der gewonnenen Ergebnisse konnte ein Schema fÜr den thermischen Abbaumechanismus des Polyäthylens aufgestellt werden.Weiterhin ist es mÖglich, im Pyrolyse-Chromatogramm unterschiedliche Verzweigungsgrade von Polyäthylenen zu unterscheiden.

---

---

Dedicated to Professor Dr. Dr. h. c. Stefan Goldschmidt on the occasion of his 75th birthday.

---

This paper is part of the work carried out by K. H. Kaiser at the Technikum fÜr Chemie und Physik Dr. GrÜbler, Isny/Allgäu, for his chemical engineering degree.

---

Part I: Cieplinski, E. W., and co-workers.     

The analysis of lubricating oil additives by supercritical fluid chromatography with packed and open tubular capillary columns

Lubricating oil additives have been analyzed by supercritical fluid chromatography on open tubular and packed capillary columns. Carbon dioxide and modified carbon dioxide were used as mobile phases and detection was accomplished by flame ionization and micro UV. Rapid and efficient analysis of the lubricating oil additives was demonstrated.     

Graphite layer open tubular (GLOT) columns in gas chromatography and environmental analysis

Summary The preparation of graphite layer open tubular (GLOT) columns is described together with their application to the analysis of priority pollutants and polar compounds such as alcohols, free carboxylic acids, aliphatic amines and phenols at the sub-nanogram level.A specific application of GLOT columns is for the direct analysis of aqueous solutions avoiding solvent extraction procedures. Several chromatograms of critical separations are reported together with calibration curves. A study of the reproducibility of column preparation is reported in terms of the standard deviation of the capacity ratio and of the minimum HETP obtained.     

The efficiency of open tubular gas chromatographic columns

Summary A new parameter, the mean specific plate number, is proposed for assessing the efficiency of support coated open tubular (SCOT) and wall coated open tubular (WCOT) columns and for comparing the efficiency of different open tubular columns. It has the advantage over most previously used parameters in that it has only a small dependence on the partition ratio and it allows for the column diameter.A graphical presentation is given of the maximum theoretical mean specific plate number as a function of the partition ratio for SCOT columns having a range of relative porous layer thicknesses and for WCOT columns with a range of phase ratios.This presentation permits ready visual comparison of the potential efficiency of different columns and enables a simple evaluation of the percentage utilization of theoretical efficiency from experimentally determined values of the maximum mean specific plate number. For a given column the percentage utilization of theoretical efficiency at optimum average gas velocity and that at optimum practical gas velocity or at a higher average gas velocity are shown to be equal provided that corrections for column pressure drop are made.     

Increased thermostability of non-polar wall-coated open tubular columns

A method of deactivating the inner surface of glass capillary columns is described, which can be used at 350°C without detoriation. A non-polar liquid phase was prepared from a commercially available liquid phase which, when coated on a glass surface, can withstand temperatures of 325°C for isothermal analysis and 350°C for temperature-programmed analysis. After deactivation, the column was coated using the static coating method. Then it was conditioned, tested and kept for 48 hours at 35O°C before being used for the analysis of a mixture of chlorinated pesticides.     

New method for the preparation of small diameter columns with polymeric stationary phases for open tubular liquid chromatography

The purpose of this report is to introduce a new method for use in coating polymeric stationary phase films on the inside wall of small bore diameter fused silica capillary tubing. This technique is being developed for use in fabricating capillary columns for open tubular liquid chromatography.     

Preparation and evaluation of 3 m open tubular capillary columns with a zwitterionic polymeric porous layer for liquid chromatography

A 3 m zwitterionic polymeric porous layer open tubular column (3 m × 25 μm id × 375 μm od) with a polymeric porous layer thickness of 4 μm was fabricated by the copolymerization of [2‐(methacryloyloxy)ethyl] dimethyl‐(3‐sulfopropyl) ammonium hydroxide and N,N’‐methylenebis(acrylamide). The effects of the diameter of the capillary, reaction temperature, and polymerization time on the preparation of the open tubular column were investigated. Characterized by scanning electron microscopy, the zwitterionic layer was observed to be rough and throughout the fused‐silica capillary homogenously, which increased the phase ratio. The separation of neutral, basic, and acidic compounds demonstrates the strong hydrophilicity of the poly[2‐(methacryloyloxy)ethyl] dimethyl‐(3‐sulfopropyl) ammonium hydroxide coating. In addition, the poly[2‐(methacryloyloxy) ethyl] dimethyl‐(3‐sulfopropyl) ammonium hydroxide porous layer open tubular column was applied for the analysis of flavonoids from the rootstalk of licorice, revealing the potential in separating complex samples. The relative standard deviation of retention time for run‐to‐run (n = 5), day‐to‐day (n = 3), and column‐to‐column (n = 3) of toluene, N,N‐dimethylformamide, formamide, and thiourea were below 1.2%, exhibiting good repeatability.