Extending the applicability of gas chromatography

Gas- en vloeistofchromatografie zijn de twee belangrijkste technieken in de analytische scheikunde, vooral in combinatie met massaspectrometrie. Beide technieken worden op tal van terreinen toegepast. De laatste jaren zijn met name de toepassingsmogelijkheden van vloeistofchromatografie toegenomen. Zowel in laboratoria als in wetenschappelijke publicaties wordt gaschromatografie steeds minder toegepast en bestudeerd. Dit is onterecht, betoogt Erwin Kaal. Met zijn onderzoek laat hij zien dat gaschromatografie de beste keuze is voor veel soorten analytische vraagstukken. Kaal richtte zich vooral op het vergroten van het toepassingsgebied van gaschromatografie (GC) en gaschromatografie gekoppeld aan massaspectrometrie (GC-MS). GC(-MS) wordt in de meeste laboratoria voornamelijk gebruikt voor de analyse van monstermaterialen die alleen vluchtige, apolaire bestanddelen bevatten. GC-MS is echter ook bruikbaar voor het analyseren van verschillende andere materialen die (ook) andere moleculen bevatten. Om de analyse van grote moleculen en/of polaire (biologische) moleculen met GC(-MS) mogelijk te maken ontwikkelde Kaal nieuwe analytische (monsterintroductie)technieken. Hij ontwikkelende tevens geautomatiseerde methoden voor het modificeren van moleculen die te groot of te polair zijn om direct geanalyseerd te kunnen worden met GC en hij koppelde vloeistofchromatografie aan gaschromatografie voor het multidimensionaal karakteriseren van grote moleculen

Comprehensive two-dimensional liquid chromatography and hyphenated liquid chromatography to study the degradation of poly(bisphenol A)carbonate

Size exclusion chromatography (SEC), gradient polymer elution chromatography (GPEC) and liquid chromatography at critical conditions (LC-CC) have been developed and applied to observe chemical changes in poly(bisphenol A)carbonate (PC) due to hydrolytic degradation. Especially LC-CC appeared to be very successful to observe differences in functionality of PC as result of hydrolytic degradation. Observed differences due to degradation could be identified by (semi) on-line coupling to matrix assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The differences in functionality could be attributed to the formation of different end-groups, i.e. OH end-groups. In addition, comprehensive two-dimensional liquid chromatography (2D-LC) has been applied successfully to study the hydrolytic degradation of PC. LC-CC x SEC showed that the formation of PC with different end-groups occurred over the whole molecular mass range. This information could not be obtained with the separate liquid chromatographic techniques, thereby illustrating the added value of 2D-LC. © 2005 Elsevier B.V. All rights reserved

Towards early detection of the hydrolytic degradation of poly(bisphenol A)carbonate by hyphenated liquid chromatography and comprehensive two-dimensional liquid chromatography

The hydrolytic degradation of poly(bisphenol A)carbonate (PC) has been characterized by various liquid chromatography techniques. Size exclusion chromatography (SEC) showed a significant decrease in molecular mass as a result of hydrolytic degradation, while 'liquid chromatography at critical conditions' (LC-CC) was very successful for observing differences in functionality due to degradation, i.e. the formation of OH end-groups. To characterize and identify the observed differences semi on-line coupling of liquid chromatography to matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and Fourier transform infrared spectroscopy (FT-IR) has proved to be very useful. Comprehensive two-dimensional liquid chromatography (2D-LC) was also applied to study the hydrolytic degradation of poly(bisphenol A)carbonate. LC-CC × SEC showed that the formation of poly(bisphenol A)carbonate with OH end-groups occurred over the whole molecular mass range. This information could not be obtained with the separate liquid chromatographic techniques, thereby illustrating the usefulness of 2D-LC. The main degradation processes of poly(bisphenol A)carbonate under the applied hydrolysis conditions turned out to be disappearance of cyclic PC oligomers, chain scission of PC and (subsequent) formation of OH end-groups. FT-IR, SEC and LC-CC have been used to follow the hydrolytic degradation with time. LC-CC proved to be the most promising technique to detect the degradation of poly(bisphenol A)carbonate at an early stage. © 2005 Elsevier Ltd. All rights reserved

Hyphenation of aqueous liquid chromatography to pyrolysis-gas chromatography and mass spectrometry for the comprehensive characterization of water-soluble polymers

A recently developed hyphenated system for "organic" size-exclusion chromatography-pyrolysis-gas chromatography-mass spectrometry (SEC-Py-GC-MS) is adapted to allow the use of aqueous LC eluents as applied in the characterization of water-soluble polymers. The system uses syringe-based transfer of multiple LC-fractions to the GC instrument with solvent elimination and subsequent pyrolysis in a programmed temperature vaporization injector. The problems of the large-volume injections of aqueous, salt containing eluents into the Py-GC-MS are solved by using a ‘sintered-bed liner’ for elimination of the water at a high temperature, a volatile salt and the installation of a back-flush option. After optimization, the system was applied for the determination of the combined molecular weight-chemical composition of a polyethylene glycol-polypropylene glycol block copolymer. This analysis was done with the system in the aqueous SEC-Py-GC-MS mode. Also demonstrated is the automated at-line characterization of a random polystyrene-polymethylmethacrylate copolymer, now with the system in the gradient reversed-phase LC-Py-GC-MS mode. The methods proposed in the present work are very useful for the detailed characterization of water-soluble copolymers