I am analyzing Metformin in Plasma Samples using Acetonitrile + DI Water with 0.5% Formic Acid. How I can Obtain Reproducible Results and Peak Shapes? Suggestion: Try by substituting Formic Acid in DI Water and adding Ammonium Acetate (10 mM) and Acetic Acid (1%) to the Aqueous Phase. This should improve the Reproducibility of Peak […]
No, it is an evolution of standard, high purity, based deactivated, type-B silica with a very stable and unique surface that does not retain water as all other HPLC columns do. If you are using a commercially available silica based HPLC column, TYPE-C™ columns may be considered the same as what you are currently using […]
No, the Cogent 4um and 2.o TYPE-C Silica™ based stationary phases are not available as unpacked bulk material. TYPE-C Silica™ is a very unique material and to properly pack columns or capillaries requires proprietary technology. For this reason, it is only sold in a pre-packed column format. However, 10um particles can be made available upon […]
It always depends on the individual compounds but generally speaking ANP is best suited to compounds of a more polar nature. In contrast, steroids as a class of compounds are mostly too hydrophobic for ANP and hence are generally poorly retained under these conditions. Reversed phase may be a more suitable chromatographic approach for retention and […]
Yes, you can. However, some labs react acetone with primary amines (+heat) to form acetone adducts (imines) in GC and GCMS. This reaction while using acetone as a mobile phase component in LCMS along with primary amines as part of the sample is something to consider. This reaction, according the University of Liverpool requires a primary amine, a ketone or aldehyde (in this […]
Using only Acetonitrile and Water and no additives is fully compatible with the Column and will not damage it. We might however recommend having 0.1% Formic Acid during Column Storage to help inhibit bacterial growth. You should change your Aqueous Solvent more frequently in this case for the same reason. If you find the Peak […]
The Cogent TYPE-C™ Silica columns have certain specification ranges for pH that must be followed to avoid damage to the material. These specifications apply to the mobile phase eluent present in the column. The amount of sample injected is so small compared to the mobile phase eluent that the effect is not significant. Therefore you should be able to inject […]
To answer this question, first we must define what Tanaka plots are. Nobuo Tanaka devised a set of chromatographic tests that are intended to characterize the properties of a given stationary phase. The analyst performs a separation of various test solutes in the manner described by the Tanaka test and records the resulting chromatographic values obtained […]
For Cogent TYPE-C™ Silica using a Transition Metal Catalyst, What if is the Presence of any Trace Quantity on the Surface and how did you measure this?
This is an issue we considered a long time ago. We intentionally ran the bonding Reaction at high Catalyst Concentration in order to actually reduce some of the Pt and Deposit it on the Surface. This produced a Visual Confirmation as the surface became Gray. Next we ran some Compounds that we knew would interact […]
High Pressure Develops after Flushing a Cogent Diamond Hydride Column with Acetonitrile, Cause and Solution. FAQ.
Question: I was running a method using an ammonium acetate-based mobile phase and decided to clean the column. I flushed it with Acetonitrile but noticed the Column pressure was higher than before when I returned to my method. What happened? Answer: The problem is most likely the Solubility of Ammonium Acetate in pure Acetonitrile. We […]
How can I restore my Diamond Hydride HPLC column? I ran out of mobile phase in my B solvent and air was accidently introduced into it and my analytes are not retaining now.
Although you should never let any HPLC column dry out, your column is probably not ruined. However, It could take days to get it restored when conditioning it with your mobile phase. If there is air in the column, give it a few hours of slow flow rate of your mobile phase or use isopropanol […]
For all new Cogent TYPE-C™ HPLC columns with the exception of new Diamond Hydride™ columns, all one needs to do is run 7-10 column bed volumes of your mobile phase through the column at your normal flow rate. Then it is best to inject a known standard and repeat the injections until duplicate chromatograms are […]
Aqueous Normal Phase (ANP) is a distinctly different retention mode than Hydrophilic Interaction Liquid Chromatography (HILIC). In HILIC, evidence has shown that retention is achieved by partitioning in and out of a water layer surrounding the stationary phase surface. With a much less polar surface, TYPE-C Silica columns do not exhibit this same partitioning retention behavior. Speculated local […]
It depends on the type of samples you are working with. The purpose of cleaning the column is to remove contaminants that build up on the column from your samples. As such, injecting clean samples such as standards mean that the column will rarely need cleaning. On the other hand, biological or physiological samples have […]
This Saw Tooth Pattern may be due to the presence of an Immiscible Solvent remaining in the Column. Even trace amounts of these Solvents can cause issues. The Immiscibility manifests as an unstable Baseline, such as the Example shown below. Suggestion: In order to fix this issue, try flushing the Column overnight with a mutually […]
This article describes how best to prepare Cogent TYPE-C Silica™ HPLC Columns for Initial Use when you first receive them as well as How To Store them, for either Overnight or Long-Term Storage, to prevent Column degradation. Storage Solvents for Reverse Phase (RP) or Aqueous Normal Phase (ANP): If RP and ANP are your desired next use […]
I am using a Cogent TYPE-C™column with LC-MS and solvents containing 10 mM ammonium acetate. I noticed that my source was getting white film on it. At the same time the background noise was very low. Is my column bleeding the packing material?
Cogent TYPE-C™ columns including the Cogent Diamond Hydride have a very low background noise even when used with LC-MS and the white film most likely comes from ammonium acetate build up from your mobile phase. These columns have been proven to be extremely durable and because of the direct silicon-carbon bonds of these phases, bonded phase bleed is almost […]
I have Broad, Split Peaks in an ANP Method with Acetonitrile/Methanol Diluent, What can I do to Improve Peak Shape?
I am analyzing Pyrazinoic Acid by Aqueous Normal Phase HPLC (ANP) using the Cogent Diamond Hydride™ Column. I observe two broad, Split Peaks for the Analyte. I am using an Acetonitrile/DI Water/Formic acid based Mobile Phase and my diluent is 50/50 Methanol/Acetonitrile. Retention is also low. What can I do to improve peak shape and/or […]
I heard that there is Not a Good Alternative to HILIC to Achieve Sufficient Retention for some compounds. Is this true? – FAQ
This is an untrue statement that can lead chromatographers to frustration as THERE IS an alternative mode of chromatography that surpasses HILIC in reproducibility, precision and the ability to separate both hydrophobic and hydrophilic compounds. It is well documented that Aqueous Normal Phase HPLC (ANP) is a very viable alternative to HILIC for polar compounds and in many cases superior […]
Is TFA or Formic Acid better for an Acidic Mobile Phase Additive for Cogent TYPE-C HPLC columns? Suggestion: Whether you choose Formic Acid or Trifluoroacetic Acid (TFA) as your Mobile Phase Additive for optimal results will depend on several factors. TFA, in most concentrations is Incompatible with some Detection Methods such as Mass Spectrometry and […]
Yes, it is and it has all the advantages of ordinary, market leading high purity, type-B silica supports for HPLC.
Many other column suppliers suggest different columns for Acids, Neutrals or Bases, which TYPE-C™ column is best for each of these compound groups?
The Cogent TYPE-C™ HPLC phases are unique in that they have different retention mechanisms which can be exploited to give unique separations. It may not be necessary to use different columns for different classes of compounds. Click here for real life examples of the Cogent TYPE-C™ and other HPLC columns separating many very different types of […]
While some types of analyses for compounds have traditionally required a high mobile phase pH (e.g. up to 10, 11 or 12) in order to get acceptable chromatographic retention due to a high pKa, it is not necessary to use high pH to get retention. These extreme pH conditions can be damaging to any HPLC […]
When you first receive a Cogent™ HPLC column, its performance should be checked by running a quick test to measure peak symmetry and efficiency. The column you purchased came with a Packing Test Chromatogram that shows the original QC values (peak shape, plate count) of test solutes under specified conditions. When you follow the conditions in that test […]
All nucleotides are are comprised of the following sub-structures: A nucleobase, a 5-membered ring sugar unit (either ribose or 2-deoxyribose), and one or more phosphate groups. In the case of inosine nucleotides, the nucleobase is hypoxanthine. When a ribose unit is attached to hypoxanthine via a β-N9-glycosidic bond, it is known as the nucleoside inosine. It is the presence of […]
What are some examples of third-party journal articles that feature the Cogent™ HPLC columns in metabolomics studies?
There are many examples of the Cogent™ HPLC columns used in metabolomics research, which have been published by third-party researchers in peer-reviewed scientific journals. Two notable works are described here. The first one, performed by Dr. Kyu Rhee and co-workers of Weill Cornell Medical College, uses the Diamond Hydride™ column to understand the pathogenic mechanism […]
What are the cost advantages of Cogent TYPE-C Silica columns over HILIC, mixed mode, and ion exchange for LC-MS and preparative applications?
There are several reasons why the Cogent TYPE-C™ Silica is preferred to HILIC, Mixed Mode, or Ion Exchange phases in terms of total cost to the end user. 1. With HILIC columns, you need to have 25–50 mM concentration of a salt present in the mobile phase in order to get polar compounds to elute from […]
When using the Cogent TYPE-C™ HPLC Columns in Aqueous Normal Phase (ANP) mode, which is the best Mode for Hydrophilic Analytes, you should expect the same Sample Loading Capacity as you would expect in typical, ordinary Normal Phase HPLC or HILIC, which is not the same as what you might expect for ordinary Reversed Phase […]
For chemical bonds in traditional, ordinary type B silica based materials, the organosilane starting material is Si-O-Si-C and this reagent is reacted with the silica to form the final stationary phase which includes a Si-O-Si-C ligand. This is in contrast with the Cogent TYPE-C™ phases in that the Si-C bond is formed directly as part of the […]
“Base-deactivated” means that the Column is designed for analysis of Basic Compounds. Conventional Columns Based on Type B Silica typically have Si-OH groups on the surface that interact with bases. This Secondary Retention Mechanism is typically Undesirable and causes poor Peak Shapes. The following are two ways that Reversed Phase HPLC columns can get around […]
Aqueous normal phase chromatography (ANP) is a chromatographic technique which encompasses the mobile phase region between reversed-phase chromatography (RP) and organic normal phase chromatography (ONP) used mainly to separate polar compounds such as acids, bases and peptides.. Using a hydrophobic stationary phase such as silica hydride (available as Cogent TYPE-C™ HPLC columns) a mobile phase of 98% organic […]
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 chromatography (RP) and organic normal phase chromatography (ONP) and is used mainly for polar compounds. In normal phase chromatography, the stationary phase is polar and the mobile phase is nonpolar. In […]
The stop depth or seating depth is the distance between the end of a ferrule and the end of a section of tubing in the inlet port of the column. If the stop depth is too short, there will be a gap between the tubing and the column inlet. On the other hand, if the distance is too long, the ferrule will not seat properly in […]
The biggest difference is the surface chemistry and how it will benefit you. The dominance of silicon hydride (Si-H) groups instead of the “silanol group” (Si-OH) common to all irregular or spherical Type A & B silica based phases changes the general character of the column; ie solvents will adsorb and desorb differently and much […]
The bubbling of gas / liquid that can rarely occur when you remove the end plugs from a brand new Cogent TYPE-C™ column is harmless and does not indicate that the column is damaged. The escaping gas is a result of the residual solvents and or reagents that were used in the chemical synthesis of […]
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 manner, the stationary phase is essentially in equilibrium with the wash solvent, so it may still take a long time to remove contaminants from […]
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 silica B based materials, the organo-silane starting material is Si-O-Si-C4-Phenyl and this reagent is reacted with the silica to form the […]
What Problems can Occur When Using a Dedicated Reversed Phase HPLC Instrument for ANP Method for the first time.
When a system is constantly run in Reversed-Phase (RP) HPLC, many Contaminants are retained, coat Seals, Frits, Check Valves and many other parts of an HPLC System. When these Contaminants build up, often it is time to replace them during a PM (Preventative Maintenance). It is important to note that when a system is used […]
Column temperature* is a useful but often overlooked variable in HPLC separations. In reversed phase (RP), retention generally decreases with increasing temperature. For this reason, higher temperature can often be successfully used to speed up a method’s run time. Furthermore, solvent viscosity decreases at higher temperatures, so pressure is lower and this allows for higher flow […]
Not normally! Trifluoroacetic Acid (TFA) will not Alter the Column Chemistry of Cogent TYPE-C Columns. If you have a Method that uses Formic Acid for example and then try a TFA Method, you can go back to the Formic Acid Method and obtain the same Retention behavior as before. Use of TFA does have other […]