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What capacity of vacuum pump should I use with an SPE vacuum manifold?
Asked Feb 16, 2022
In order to achieve consistent flow rates when running multiple tubes simultaneously it is advisable to use a vacuum pump which can generate a vacuum equivalent to 20" of mercury.
What impact does temperature have on GPC separations using Phenogel?
Asked Nov 16, 2020
Temperature typically only has minor impacts on GPC separations, but it should be considered nevertheless. Elevating the column temperature can help improve solubility of some analytes which may improve the resolution of poorly soluble analytes. Further, increased column temperature can also reduce mobile phase/diluent viscosity mismatches which can improve the performance of a separation. One caution one must consider with elevated temperature relates to the flash point or boiling point of your mobile phase solvent. Although it is sometime tragically overlooked, one does not want to do a separation at a temperature anywhere close the flash point of a mobile phase.
What solvent should I use for my separation using Phenogel?
Asked Nov 16, 2020
The main factor on solvent use is solubility. What solvent is your analyte soluble in? That will dictate the mobile phase used for your separation because your analytes must be soluble in the mobile phase to be separated by the column. Sometimes poor resolution or low recovery of an analyte can be caused by poor solubility of the analyte in the selected mobile phase.
How do I prepare my samples for N-Glycan analysis?
Asked Oct 1, 2020
The Glycans are typically released from the proteins by PNGase F in buffer solution and then labelled using 2-AA or 2-AB. The samples can then be cleaned up using a HILIC based SPE sorbent such as the bioZen N-Glycan Clean-up plate under typical HILIC conditions to remove excess labeling reagent, salts and surfactants.
What are the retention mechanisms of Rezex H+ and how can they be influenced?
Asked Feb 2, 2016
Rezex H+ separates analytes isocratically based on three different separation modes: GFC for sugar residues, ion exchange interactions for organic acids, and reversed phase for organic compounds (glycerol and ethanol). The size exclusion mechanism is most influenced by flow rate. The ion exchange mechanism can be influenced by pH and temperature. The reversed phase interactions are influenced by primarily by temperature.
At what pressure are Verex 20mm Pressure release seals designed to break?
Asked Mar 28, 2016
Pressure is released at 3.0 +/- 0.5 Bar (1 Bar = approximately 14.6 PSI)
The pressure release will split and vent to prevent the seal and vial from breaking. This prevents instrument down time and provides added lab safety
Only use pressure release for high temperature work
For the highest quality vial and cap products, we recommend Verex. Our vials and caps are manufactured to provide high quality, state-of-the-art solutions for your most challenging, sensitive applications.
What should I consider when chosing between Kinetex phenylhexyl, biphenyl and F5?
Asked Jul 21, 2020
Kinetex phenylhexyl is best suited to the separation of aromatic compounds which are relatively hydrophobic. It can also be used as an alternate selectivity to a C8 or C18, retaining compounds to a similar extend compared to a C8, but with the additional pi-pi interations allowing for aromatic positional isomers to be separated. Kinetex biphenyl is more applicable to polar aromatic compounds, and will also offer a good degree of shape selectivity. Kinetex F5 is the most polar phenyl phase, due to it's highly polar nature and the interactions it can undergo with analytes it is the best option for analyzing highly polar analytes, and those compounds which differ in terms of pi electron structure.
Which C18 columns are most appropriate for preparative separations?
Asked May 9, 2017
Phenomenex has a variety of preparative C18 columns to choose from. If the you are looking for a material that can handle large sample volumes then Luna C18(2) would be the best option. Gemini NX-C18 offers extended pH stability for high pH analyses and a different selectivity to Luna C18(2). Kinetex core-shell columns are best suited for those who are looking for high efficiency preparative applications often where closely eluting impurities pose a problem. Kinetex C18 is also fully scalable from UHPLC to Prep so it is perfect for labs that require the same selectivity across multiple particle sizes. Luna Omega Polar C18 and PS C18 offer a different selectivity to more traditional C18 phases and would be ideal for analysts who need a different selectivity or greater retention of polar compounds.
What filters do you recommend for use prior to ion chromatography?
Asked Oct 14, 2020
PES (polyethersulfone) syringe filters show low non-specific binding for ionic species, this combined with their hydrophilic properties make them a good choice when the filtration of ionic species is required.
What impact does changing the alkylamine have on the separation of oligonucleotides?
Asked Oct 1, 2020
The alkylamine used directly affects retention time, with longer chains leading to increased retention, e.g. hexylamine will show longer retention times than triethylamine. There is also a difference in solubility so generally gradients need to be adjusted to allow for this. Generally, the effect of ion-pair is oligo-specific; for example, Gapmers longer amines offer better resolution whereas for siRNA shorter amines offer an improvement in resolution.