Over the years, many chromatographers have been given the task to develop HPLC and LCMS methods for polar compounds. Those who have chosen HILIC columns often report their gradient methods are problematic causing them frustration, more method development time and additional costs. Mostly the complaints are the “downtime” between runs that HILIC and all ordinary […]
Category: HPLC Column Information
EDTA plasma samples for creatine & creatinine – Blog.
Since we have done work with creatine and creatinine in urine, see appliction note we been asked about measuring levels of these compounds in EDTA plasma samples. It should be possible unless there is some interference from the EDTA; we have not measured EDTA retention under these conditions (where we determined creatine and creatinine). Obviously plasma is a different matrix […]
Fosetyl-Aluminum Analysis by HPLC. Optimizing Tips.
You can use the Cogent Bidentate C18™ column in reversed phase (RP) with a high water content method. According to a 2014 third-party research article, if the analysis is done by reversed phase an ion pair agent is recommended to increase retention and reduce peak tailing. Here, 8 mM sodium sulfate was used in a […]
How can I separate methacrylic acid and dodecyl benzene sulfonic acid?
Good retention and peak shapes have been observed for similar compounds. Methacrylic acid is similar in structure to acrylic acid, which can be well-retained with a mobile phase of DI water + 0.1% formic acid and a Bidentate C18 column. Dodecyl benzene sulfonic acid has some of the same functional groups as docusate sodium, which also has […]
How do the Terms Nano, Capillary, and Micro-LC Differ in Terms of Column ID and Typical Flow Rates?
The following table shows the flow rate and column ID ranges for the various terms which is generally accepted by chromatographers but definitions may differ from different sources. Term Colum i.d. range (um) Flow rate range (uL/min) Nano 25–150 0.02–1 Capillary 150–500 1–10 Micro 500–1000 10–50
How does a Pulse from an HPLC Pump Affect the Column and its Performance?
If your HPLC pump produces a “pulse” (i.e. cyclic fluctuation in flow/pressure), this can cause problems for your Method and Column. The pump will not be delivering optimally Precise/Accurate Flow and this can cause your system to not meet System Suitability Criteria as well as other issues. Sudden changes in the Pressure can also cause […]
How to analyze phosphorylated compounds with the Cogent Diamond Hydride™ column by HPLC.
Phosphorylated compounds can be difficult to analyze by HPLC. However, a wide variety of compounds with the phosphate functional group have been able to be retained with the Cogent Diamond Hydride™ column in ANP mode. Examples include phosphorylated sugars, herbicides, and nucleotides. The strategy can also be applied to other compounds of this type such […]
How To Choose a Cogent HPLC Column. Order of Hydrophobicity.
The first thing to consider is the chemical structures of the Analytes in your Sample and the corresponding most suitable Retention mode for them. For Reversed Phase, the general order of Stationary Phase Hydrophobicity (and therefore retentiveness in RP) is as follows (left to right) and for hydrophilicity (and therefore retentiveness in ANP) is shown […]
How To Condition Cogent RP, HPS & Axis HPLC Columns for Storage.
For Cogent RP™, Cogent HPS™ & Cogent Axis™ HPLC Columns Long Term Storage: Rinse the Column with 8 Column Volumes with pure Solvent that you use as your mobile phase. It is important to use non-buffered Mobile Phase. Then purge the Column with 8 Column Volumes of 100% HPLC Grade, Filtered Isopropyl Alcohol. Then purge […]
Hydrophilic & Hydrophobic peptides analyzed by LCMS in ANP
The Cogent Diamond Hydride™ HPLC columns using aqueous normal phase (ANP) chromatography are very good choices for LCMS or HPLC analysis of most peptides. We have published an article on peptides demonstrating the ability of the column to retain a very broad range of peptides. This paper uses experimental, capillary ID columns but it works just as well with standard […]
I heard that there is Not a Good Alternative to HILIC to Achieve Sufficient Retention for some compounds. Is this true?
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 […]
Types of isomers and suitable HPLC columns for separation
There are many types of chemical isomers, and each may require different approaches to obtain chromatographic separation. Some examples are as follows: Empirical Isomers: These compounds have the same empirical formula but the atoms could be arranged in any possible configuration. This is the most general type of isomer. Knowing all of the possible isomers […]
Use a Cogent TYPE-C™ column to develop methods instead of columns you have experience with many benefits?
There are many reasons to use Cogent TYPE-C columns for new methods. Below are some of the reasons and attached is a White Paper that provides a concise argument. Often gradients are required to cope with large differences in polarity of multiple compounds in a mixture. With TYPE-C™ columns there always is the possibility to achieve […]
Using different Cogent™ HPLC stationary phases for different selectivity.
Each of the Cogent™ stationary phase materials has a different bonded ligand and therefore potential for different selectivity of given analytes. Consider the example, featuring the Cogent Bidentate C18™ and Cogent UDC-Cholesterol™ columns in another Knowledge Base article: https://kb.mtc-usa.com/article/AA-00781 Note the two columns give substantially different retention for the same analytes under the same conditions. As […]
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, tretinoin, and tazarotene), we compared the Cogent Bidentate C18™ and Cogent UDC-Cholesterol™ columns at different temperatures in an attempt to gain insight into their retentive behavior. The […]
What are the differences between Cogent Amide columns and all the other Amide brands on the market?
The Cogent Amide HPLC column is very polar and effective for compounds that have amines as well as sugars such as galactose, sucrose, glucose and basic pharmaceuticals such as Prozac, Tizanidine and others. The Cogent Amide™ column is made with TYPE-C™ silica so it can be used in Reversed Phase, Normal Phase or Aqueous Normal Phase HPLC and […]
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 (silica hydride) perform similarly to HILIC columns as far as polar compound retention in a “Normal Phase” elution order is concerned. With both types of columns using higher than 70% organic composition of the […]
What is the most polar Cogent TYPE-C HPLC column?
The most polar HPLC stationary phase manufactured by MicroSolv Technology Corporation is the Cogent Amide™. It is very robust compared to most other “amide” columns and can be very effective for compounds such as sugars and other carbohydrates but also for compounds with amines. The Cogent Amide™ column is made with TYPE-C™ silica so it […]
When to use PEEK over stainless steel for HPLC column Harware.
Data in certain types of analyses may be adversely affected by use of stainless steel HPLC columns. In these cases, you may want to consider a column housed in PEEK hardware instead of traditional stainless steel. Mainly used in Ion Chromatography and for some bioactive compounds, PEEK columns may circumvent the issues associated with stainless […]
Which column do you recommend for the separation of positional isomers by HPLC or LCMS?
The answer to this question depends on what type of positional isomers. For reversed phase separation of aromatic positional isomers, the Cogent Phenyl Hydride™ is often a good choice. These isomers may differ in their electron density of the aromatic ring due to the positions of the various substituents that may be present. These differences […]
Which Column would you Recommend for a Bromhexine HPLC Assay Method?
I am currently using the following Method for analysis of Bromhexine. What Column and/or alternative Method Conditions can you Suggest? Mobile phase: Potassium di-hydrogen phosphate buffer(take Potassium di-hydrogen phosphate 1.0g, add 900ml DI Water, then change pH to 7.0 with 0.5mol/L NaOH solution, and dilution it to 1000ml by DI Water )-acetonitrile(20:80), Column temperature: 40C, Wavelength:245nm […]
Which HPLC column diameter should I use for LC-MS?
For most standard HPLC applications such as UV detection methods, a 4.6mm or 3.0mm I.D. is suitable. Lower diameters will present unnecessary problems for standard UV methods. For instance, the system tubing and especially the flow cell may cause band broadening with a 2.1mm column due to extra-column dispersion effects. With most LC-MS (as well as some other […]
Which HPLC column do you suggest for analysis of carotene or lycopene?
With these types of compounds, the main challenge will be separating the different isomers. There are numerous double bonds in the molecules, and many combinations of cis/trans isomers are likely to be encountered. Because the isomers differ little in hydrophobicity but significantly in shape, a column with shape-selective capabilities would be required for an adequate separation. Reversed […]