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31 Development guide for ANP or Aqueous Normal Phase HPLC methods

Why ANP is better than HILIC for most polar compound methods HILIC will require more time to equilibrate, more salt to retain compounds, lacks RT precision and lifetime of the columns is short. With ANP…

32 Difference between adsorption and absorption. For Chromatographers.

Although these two terms sound similar, they are actually quite distinct and should not be confused. • Adsorption is the adhesion of a substance to a surface. This process creates a film of the adsorbate…

33 Do Cogent TYPE-C Silica™ stationary phases for HPLC have a partial positive charge? If so, is retention for basic compounds reduced because of this?

No, studies using zeta potential experiments have shown that the Cogent TYPE-C Silica™ stationary phases have a negative charge due to the presence of hydroxide ions on the surface. Retention for basic…

34 Factors that affect Sensitivity in HPLC.

Sensitivity of an HPLC chromatogram can be said as the ability to observe all analytes in sample, even a very small quantity. One of the most important factors in sensitivity is the "Signal to Noise Ratio"…

35 Fittings Definition: Screw Thread Call-Out.

What is a Thread Call-out for "English" fittings? This is a common system for describing the threading on a fitting that uses the English method. The Thread Call-Out normally consists of two numbers where…

36 For sugars analyzed by LCMS, sodium acetate is added to obtain greater sensitivity of Na adducts. Could you do this using ammonia instead, observing the NH4 adducts?

In LCMS, you will get much better sensitivity of Na-sugar adducts in the EICs compared to sugars themselves. The same principle will work for NH4 adducts as well, but there are notable drawbacks. The…

37 Fosetyl-aluminum analysis tips by HPLC

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…

38 High baseline noise with Cogent Diamond Hydride column

One reason background would be high is if something was injected that was stuck on the column and it is bleeding off or if harsh pH conditions were used. Either of these can occur sometimes without the…

39 How can I calculate the ligand density of a bonded phase?

The ligand density can be calculated using the Berendsen-de Galan equation: α = 106 %C/(102 MW carbon nC – %C MW ligand) SBET where α is the ligand density (µmol/m2), %C is the percent carbon (%),…

40 How can I fix an issue of split peaks and a high column pressure in HPLC or LCMS?

This is most likely due to "channeling" of the flow pattern inside the column. The packed bed uniformity has been disrupted and the split peaks and high pressure are indicative of this. In this case,…

41 How can I get separation of tartaric and malic acid in a complex mixture?

Suppose you have a sample containing lactic acid, glycolic acid, formic acid, L-tartaric acid, DL-malic acid, and succinic acid. The Cogent Diamond Hydride™ HPLC column will be an excellent column choice…

42 How can I obtain a flat baseline in gradient mode besides using "blank subtraction" in HPLC?

There is another way you can obtain a flat baseline besides "blank subtraction" but it can be a little tricky. It is called "absorbance matching". Typically when your B solvent is mostly acetonitrile,…

43 How can I separate capsaicinoids in hot sauce by HPLC?

If you have a hot sauce extract containing nordihydrocapsaicin, capsaicin, dihydrocapsaicin, and homodihydrocapsaicin, the Cogent Bidentate C18 2.o™ HPLC column is a good choice for sufficient separation…

44 How can my finger tight fitting be producing band broadening in HPLC?

Most chromatographers may not realize it but if fittings are not properly set and a perfect connection is accomplished, a dead volume can occur that does not get swept. This extra volume can cause band…

45 How do autosampler vials cause missed injections?

HPLC instrument manufacturers require "Fit and Form" specifications for vials used in their autosamplers. These include minimum and maximum vial dimensions for height, neck, shoulder and outer dimensional…

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