Carel A . Cramers

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Most sample-enrichment procedures currently available rely on adsorption of the analytes of interest by a suitable adsorbent material. Although good performance can be obtained for many practical problems, in some cases the applicability of adsorptive sample preparation falls short, particularly for the enrichment of polar and/or high-molecular-weight(More)
The performance of the sorbent polydimethylsiloxane (PDMS) is compared to that of the adsorbents Carbotrap and Tenax for the enrichment of volatile and reactive sulfur compounds. These included: 1- and 2-propanethiol, tetrahydrothiophene, 2-thioethanol and 2-ethylthioethanol. Several artifact-forming reactions were identified on both Tenax and Carbotrap(More)
Separations below 1 s of a mixture of organic compounds ranging from C5 to C8 have been performed to investigate the performance of a time-of-flight mass spectrometer in fast gas chromatography. The gaseous samples were focussed on a cold trap, and then injected after thermal desorption to obtain the required narrow input band-widths. Also, to obtain a very(More)
This paper describes the characterisation of reversed-phase liquid chromatography (RPLC) columns using thermodynamic measurements. Retention versus 1/T data were used to construct Van't Hoff plots. The slope of these plots indicates the standard enthalpy of transfer of the analyte from the mobile to the stationary phase. The standard entropy can be(More)
In 14 mongrel dogs wash-in and wash-out curves for halothane were obtained from measurements of arterial blood, mixed venous blood and end-tidal gas. From a certain point in the wash-in period the halothane concentration of arterial blood can be calculated from the halothane concentration in end-tidal gas and the blood-gas partition coefficient for(More)
A fast and reliable procedure for gas chromatographic profiling of components in ultrafiltrated uremic serum has been developed, using glass capillary columns. Sample pretreatment consists of ultrafiltration, evaporation and silylation. Some twenty components are identified by electron-impact and chemical ionization mass spectrometry. A comparison is made(More)
A method for the assay of acidic catecholamine metabolites in biological fluids using capillary gas chromatography--electron-capture negative-ion mass spectrometry is described. The method combines acetylation of phenolic hydroxy groups in buffered aqueous solution followed by pentafluorobenzyl ester formation and acetylation of aliphatic hydroxy groups(More)
A Stokesian dynamics computer simulation based method is presented for the estimation of the bed porosity of slurry-packed capillary liquid chromatography (LC) columns. A colloidally well-described reversed-phase stationary phase-slurry liquid suspension was used as a model system. The applied simulation method takes into account the velocity of the slurry(More)
In order to screen UV-absorbing solutes in large numbers of uremic serum samples, an automated liquid chromatographic method was developed. The method proved to be reliable and reproducible in more than 500 analyses. HPLC separation was performed using gradient elution on a 25-cm Ultrasphere Octyl reversed phase column, with 5 microns particles.(More)
Solubilities of some polycyclic aromatic hydrocarbons (PAHs) in supercritical carbon dioxide were measured with a procedure based on a direct on-line combination of a saturation cell to a flame ionization detector. Acenaphthene, anthrance and chrysene were selected as the test solutes. A method was developed and evaluated which enables the measurement of(More)