High-performance liquid chromatography on small particle silica gel

Abstract

Liquid chromatographic columns of 5-to 10-µ TLC grade silica gel have been packed by a high pressure, balanced density slurry technique. The columns have yielded HETP values of less than 0.1 mm at a linear velocity (v) of 1.18 cm/sec. For nitrobenzene (k' = 4.3), 15 effective plates per second were generated at 1.18 cm/sec. The HETP vs. v curve was lower than that obtained on Corasil II, a porous layer bead (PLB) adsorbent. The columns showed little loss of efficiency at high v's. The sample loading was greater than for an equal weight of PLB, but not so great as predicted by the ratio of surface areas.Porous adsorbents, such as silica and alumina, in large particle sizes (150+ µ ) have been used for many years in liquid chromatography. As the adsorbent particle diameter (dp) decreases, column efficiency should increase because of more rapid mass transfer. Snyder (1) verified experimentally for silica gel that column efficiency expressed as the HETP, (or H, Height Equivalent to a Theoretical Plate) was dependent on (dp)o s, for 20 5$ dp ^200 µ in a regularly packed column. Particles of silica smaller than 40 µ have proved difficult to pack reproducibly by dry packing techniques (/).Using small diameter kieselguhr, Huber (2) successfully packed 5-to 15-µ irregular particles by a dry-packing procedure with a controlled amount of tamping. Scott (3) preferred packing 5-to 7-µ spherical, highly cross-linked ion exchange resins in a concentrated aqueous slurry.Slurry packing has been applied to 20-µ silica gel (1), but little additional work has been reported on the successful application of the technique. This paper reports the preparation and use of columns of finely divided silica gel of a 5-to -µ particle size range which are packed by a high pressure, balanced density slurry procedure. A balanced density solvent is one that has a density equal to that of the silica so there is a minimum of particle size segregation during packing. Polystyrene-based steric exclusion chromatography packings are sometimes packed by a balanced density procedure (4). EXPERIMENTALApparatus. Columns were packed using a high pressure slurry packing apparatus shown schematically in Figure 1. A reservoir supplied liquid to a Whitey Laboratory Feed Pump Model LP-10 (Whitey Research and Tool Co., Emeryville, Calif.). This diaphragm-type pulsating pump forced the slurry from the slurry reservoir into the chromatographic column at very high flow rates and pressures. Equipped with an 8-mm plunger and 30:1 gear ratio, this pump can deliver a maximum flow rate of 1400 ml/hr and a maximum output pressure of 5000 psi.

Fast analysis in liquid chromatography using small particle size and high pressure

“…However, particles of silica smaller than 40 lm have demonstrated some difficulties with packing reproducibility. Irregular shapes of microporous particles were used throughout the 1970s [40][41][42][43], until spherical material was obtained and improved [44][45][46].…”

Separation of Azoxybenzenes and Some Derivatives by High Performance Liquid Chromatography.

“…In order to prove this, infrared analysis of the eluted peaks was carried out. The two eluted peaks for 4-chloro-'4-methoxy azoxy benzene were fractioncollected with a methanol mobile phase containing 80% v/v of methanol differential refract meter detector was used because the photoreaction of azoxy benzene derivative might be induced by ATV irradiation [12] . The same , I.R.…”

The contributions of Csaba Horváth to liquid chromatography

“…"Fast LC", "High Speed LC", and "High Efficiency LC" were used by Horvµth [6], Kirkland [9], Huber [10], Majors [11], and Karger [12], while the phrase "High Performance LC" was introduced later by Majors [13]. Still, "High Pressure LC" [14] dominated as the descriptive term well into the next decade, when "High Performance LC" slowly gained the upper hand.…”