Comparative study of the performance of spherical and angular silica and alumina supports in the 1-10-μm size range

Study of Dispersion in Packed Chromatographic Columns by Pulsed Field Gradient Nuclear Magnetic Resonance

“…The correlation coefficient, although smaller than for the fit to the Giddings equation is still satisfactory, with r 2 = 0.995 (0.991). It is important to observe that the values of the Knox constants that were derived for our column following the classical efficiency test of an HPLC column are very close to the values that are considered as typical, ,− while the values derived from PFGNMR are much lower. It has been reported that typical values for well packed columns are b = 2, a = 1, and C = 0.01 .…”

“…Equation 10 has been widely used in the literature. It explains reasonably well most experimental data. − ,− , This is in part due to the narrow range of values of the reduced velocity within which most of these data have been acquired. It is not easy to operate at high reduced velocities columns packed with the fine particle materials currently available .…”

“…Pure water was used for the PFGNMR measurements and n -butylbenzene to record the conventional plate height data. The latter compound is retained on the C18 silica stationary phase and we know that C depends on the retention factor, increasing with increasing k ‘ at low values of this factor. ,− The larger value of λ accounts for the markedly higher plate heights (approximately twice larger) observed with the conventional procedure of determination. Note that these measurements were carried out on a freshly prepared column which had not undergone full consolidation, while those reported in ref had been made after completion of the entire investigation, on a consolidated column.…”

“…On the other hand, from a chromatographic point of view at least, it is of little interest to operate them at values of ν below 1. So, in most cases, experimental correlations have been studied in the range of ν between 1 and 20 to 40. ,− , This is barely sufficient for an accurate estimate of a . In most cases, the estimates obtained for b and/or c are poorly precise.…”

A High‐Throughput Composite Catalyst based on Nickel Carbon Cubes for the Hydrogenation of 5‐Hydroxymethylfurfural to 2,5‐Dimethylfuran

“…Following the principles of column chromatography, the number of theoreticalp lates N in ac olumni sameasure of the column efficiency,w hich,a mong others, is af unctiono f the materials properties, of the column packing, ando ft he columnd imensions. [44][45][46] Here, high numbers of theoretical plates are associated with high column efficiency.E xemplarily, N was determined for the columnp ackedw ith the Ni@SAZn_ (1)],i n which t R is the retention time of toluenea nd w H is the peak width at half maximum. [46] N ¼ 5:…”