More Differences Discovered between Silica-C™ and Ordinary Silica

The Cogent TYPE-C™ line of HPLC columns are all based on a unique type of silica in which surface populated with  silica hydride groups (>95%). The difference has a significant impact on a variety of chromatographic aspects with many benefits for the users. In order to demonstrate these differences, we compared a plain silica column with an underivatized Silica-C™ column. The method conditions are shown in Table 1. A simple isocratic method with two test solutes was chosen so that meaningful comparisons could be drawn regarding efficiency and so on.

                The chromatograms obtained are shown in Figure 1 and the data is presented in Table 2. What is most notable is that the silica column could not distinguish amongst the two test solutes under these conditions, while baseline resolution is obtained using the Silica-C column. This illustrates how the hydride surface can dramatically change the behavior of the column. In terms of peak shape, the silica column exhibits significantly more tailing, possibly due to the influence of silanophilic interactions with the amine groups of the test solutes. Finally, efficiency on the Silica-C phase surpasses the silica material as well for chromatographers.

 

Table 1. Method Settings

Parameter	Description
20% Solvent A	DI H2O + 0.1% formic acid
80% Solvent B	Acetonitrile + 0.1% formic acid
Flow Rate	1.0 mL/min
Injection Volume	0.5 µL
Detection	UV 210 nm
Sample	Phenylglycine and phenylalanine, 10ppm each

 

Table 2. Obtained and calculated chromatographic values

	HPS SILICA		SILICA-C
	Phenylglycine	Phenylalanine	Phenylglycine	Phenylalanine
tR (min)	4.504	4.504	7.276	8.484
selectivity	1.00		1.22
Rs	0.00		3.60
Tf	2.37	2.37	1.11	1.29
N/column	1967	1967	9097	8645
N/meter	13113	13113	60647	57633

 

Figure 1. Overlay comparison of column data. Peak 1) phenylglycine, peak 2) phenylalanine.