The generally accepted definition for a UHPLC (Ultra High Pressure Liquid Chromatography) column is one in which the particle size is below 2 µm. Our Cogent TYPE-C Silica 2.o™ columns have an average particle size of 2.2 µm, making them “near-UHPLC” phases. The idea behind UHPLC columns is that, as particle size decreases, peak efficiency increases dramatically. […]
We would recommend against using different particle sizes and stationary phasess for guard and analytical column combination. That being said, the Cogent 2.o™ columns are valuable so it may be worth trying and seeing if the guard column does or does not have an adverse effect on efficiency in the method. If the purpose of using a […]
The following graph shows a study investigating the day to day retention time Precision of two test solutes on the Cogent Diamond Hydride 2.o™ Column. Many factors can affect column robustness and lifetime, so it is not possible to define specific values for those parameters. Mobile Phase: A: DI H2O + 0.1% formic acid B: Acetonitrile + […]
In terms of storage, conditioning, and general use, the same protocols can be used for the Cogent Diamond Hydride 4um and Cogent Diamond Hydride 2.o™ products. The main difference between the two is of course particle size. Cogent Diamond Hydride Product Page
How do Retention and Efficiency of Asymmetric Dimethylarginine, ADMA Compare Using 4um vs. 2.o™ Diamond Hydride™ Columns?
ADMA can be retained using an ANP gradient method with the Cogent Diamond Hydride™ HPLC column. Retention times for ADMA differed only slightly between the 4um and 2.o™ stationary phases. Efficiency however was notably higher when using the 2.o™ phase. This can be readily observed from the greater peak height using the 2.o™ column in the […]
The column pressure under any conditions can be predicted using the following equation: P = (150 η L F) / (dparticle2 dcolumn2) where P is the pressure, η is the solvent viscosity, L is the column length, F is the flow rate, dparticle is the particle diameter, and dcolumn is the column inner diameter. If only the particle size is varied (same method, same column dimensions), then the factor (150 η L F) […]
What Pressure Should I Expect with a Diamond Hydride 2.o HPLC Column at Flow Rates From 0.2-2.0 mL/min?
The below data was recorded on a Waters UPLC™ system. Please note that the pressure can vary widely depending on such factors as mobile phase viscosity, temperature, column ID, and column length. The conditions shown below should clarify any questions you may have regarding this data. Column: Cogent Diamond Hydride™, 2.2um 120A, 2.1 x 50mm, cat# […]
We recommend a starting temperature of 25 °C for most applications. Generally you will see higher retention at higher temperatures and lower retention at lower ones with Aqueous Normal Phase (ANP) chromatography. This can sometimes be a useful tool for fine-tuning the retention/selectivity of the peaks. Although temperature is a variable to consider during method development, we […]