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TYPE-C Columns

31 Using temperature changes for separations of terpenoids with the Cogent Bidentate C18 and Cogent UDC-Cholesterol HPLC columns

Temperature is a useful variable to consider in HPLC separations. Control of temperature can reduce run times, alter selectivity, and change analyte efficiency. In this study of three terpenoids (bexarotene,…

32 Using the Cogent Diamond Hydride and Cogent Bidentate C18 columns together in a tandem LC separation.

If you connect these two columns in parallel but use the same mobile phase program on both columns, it will be difficult to have both reversed phase and aqueous normal phase mechanisms operating simultaneously…

33 What are the main differences between HILIC and Aqueous Normal Phase?

There are many important differences between HILIC columns and Cogent TYPE-C Silica™ columns but for the sake of brevity, we will only address the main differences. The Cogent TYPE-C™ silica columns…

34 What is Aqueous Normal Phase (ANP) and how can it help you?

Aqueous normal phase chromatography From Wikipedia, the free encyclopedia Aqueous normal phase chromatography (ANP) is an HPLC technique which encompasses the mobile phase region between reversed-phase…

35 What is the chemical structure of the Cogent DIOL stationary phase?

The Cogent Diol stationary phase structure has a single point attachment as shown below. Note this bonded phase is attached to the silica hydride surface and offers very unique retention mechanisms for…

36 What is the metal content of the silica used in Cogent TYPE-C HPLC columns?

Metal impurities testing via ICP (Inductively Coupled Plasma) analysis is peformed for the following, along with acceptance specifications: Al: Not more than 5.0 ppm Fe: Not more than 20.0 ppm Ti: Not…

37 What is the most effective way to clean HPLC columns after or before use?

Many commonly used cleaning methods feature a strong wash solvent, run isocratically in order to elute strongly retained compounds or residual solvents from the column. After some time of washing in this…

38 What is the purpose of using isopropanol (IPA) as part of the aqueous mobile mobile phase solvent in ANP methods?

Some of our Cogent HPLC column application notes that feature Aqueous Normal Phase (ANP) use 50% isopropanol (IPA) as part of the aqueous component of the mobile phase. The main reason for this use is…

39 What is the structure of the Cogent Phenyl Hydride bonded ligand? What is a "direct silicon-carbon bond"?

The Cogent Phenyl Hydride phase is a 4 carbon chain with a phenyl group at the end attached directly to the silica hydride surface with a single, direct silicon-carbon bond. With bonds in traditional…

40 What temperature should I use with the Cogent TYPE-C 2.o™ HPLC columns?

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.…

41 When is the acid group of the Cogent UDA HPLC column ionized?

The pKa of most simple carboxylic acids is in the range of ~pH 4.7-5.0. The carboxylic acid group of the Cogent UDA™ HPLC column can be either ionized or non-ionized depending on the pH of the mobile…

42 Why doesn't triphenylamine retain in ANP on a Diamond Hydride column?

There can be many reasons why any compound does not retain in any given HPLC method, however in this case, triphenylamine has three bulky phenyl groups (see structure below), which can create steric hindrance…

43 Why is it important not to exceed a mobile phase pH of 7 when using the Cogent Diamond Hydride?

Selection of too high a pH could lead to voids developing in your column. Data for the dissolution rate of silica in pure aqueous solvents as a function of pH shows significantly increasing solubility…

44 Working with plasma samples and Cogent TYPE-C HPLC columns

When working with plasma extracts, we recommend using 50% methanol/50% DI water for washing between injections. Flow rates of 0.5ml/min for 20-30 minutes for a 4.6mm x 250mm column should be sufficient.…

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