The Application Notebook
High-speed analysis of samples has always been desired for GPC analysis, however the speed of liquid chromatography measurements is directly affected by the analysis conditions. The column design is the most important point to achieve rapid measurements. The biggest hurdle to overcome is the high back pressure generated by high flow rates which constricts the column design. Polymer gel has been preferably used for size-exclusion chromatography (SEC) separation because of its variety of pore sizes, but has not been packed in columns for rapid measurement due to the concern that the high back pressure might crush the polymer gel, not allowing the column to work.
In order to solve this problem, Shodex developed a porous cross-linked styrene-divinylbenzene polymer gel with sharp particle size distribution to pack the Shodex HK column. The polymer gel successfully works to suppress back pressure, high flow rate, and GPC column for rapid measurement has been realized with the polymer gel.
The GPC column can be used for molecular weight measurement with the range from 100 to 1 million Da. The column is constructed with a 4.6 mm inner diameter and 150 mm length dimension, and has elution volume with less than 2.0 mL. It corresponds to less than 2.0 min of measurement time in case of 1.0 mL/min flow rate. At this flow rate, back pressure reaches 13.8 MPa, a suitable level for conventional HPLC or UHPLC equipment.
Polycarbonate as well as other polymers were studied at various flow rates. With each flow rate analyzed, the same results were obtained. Exemplifying SEC mode separation, can be achieved under more rapid conditions.
Poly(isobutyl methacrylate) was analyzed using two columns. The first column was the Shodex GPC HK-404L, an organic size-exclusion chromatography (GPC) column for ultra-rapid analysis, and the second column was the Shodex KF-805L, a conventional size-exclusion column. The elution volume per column of HK-404L is about 2.0 mL. The column pressure of HK-404L is low at high flow rates and the eluent can pass through the column at the same flow rate as the conventional column with the conventional HPLC instrument. The analysis time is decreased to 1/6 of conventional analysis and ultra-rapid analysis becomes possible.
HK-404L eluted the polycarbonate sample within 2 min with a 1.0 mL/min flow rate, while it took about 12 min to elute the same sample with a conventional column. The molecular weight results are comparable to conventional column. The Shodex HK-404L is a novel column ideal for the analysis polymers at a much faster rate without sacrificing the efficiency.
Shodex™/Showa Denko America, Inc.
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