Development and use of carbon adsorbents in high-performance liquid-solid chromatography : II. Reproducibility of carbon adsorbents and the influence of graphitization on their performance

Abstract

The reproducibility of the performance of carbon columns has been studied in terms of retention data and efficiency. The repeatability of the data obtained with one column over several months was excellent, in spite of its use for the analysis of a variety of samples with solvents with a wide range of eluotropic strengths. It was found that the retention data on carbon adsorbents are proportional to the total surface area of the adsorbent in the column, within the limits of error of measurement of this parameter, except for polyaromatics. For these compounds, the carbon adsorbents exhibit active sites and the retention increases faster than the surface area. Graphitization had little effect on the retention data or the eluotropic strengths of the solvents. The column efficiency for inert peaks is good, showing that excellent packings can be obtained with carbon black particles, either graphitized or not. The column efficiency decreases markedly with increasing retention, which seems to be a property of columns packed with large particles of porous adsorbents. Graphitization has also a small effect on this phenomenon and accordingly is much less useful in liquid than in gas chromatography, except in preparative applications, as the loadability is one order of magnitude greater.