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1 A case to eliminate retention time drift in ANP using the Cogent Diamond Hydride in LCMS.

We had a significant run to run RT drift ( up to 1 min for 10 repeated runs) using the Cogent Diamond Hydride™ HPLC column we ordered two weeks ago. After conditioning the column with 90% IPA and 10X…

2 A Tip to improve or obtain flat baselines in HPLC-UV gradient applications.

Due to differences in UV absorbance between two solvents at a particular monitored wavelength, you will generally observe a sloped baseline when performing gradient methods with HPLC-UV. As the solvent…

3 Acetone as the Organic Mobile Phase Component

“Green” substitute for separation of amino acids Caution: Acetone and Amines can react When working with Acetone as an HPLC solvent it is important to note that primary amines could react with Acetone…

4 Acid Washing RSA Vials has consequences

Q. What are the advantages and disadvantages of acid washing RSA Vials? A. There is no reason to acid wash RSA vials. The main reason to acid wash vials is to reduce adsorption due to native silanols…

5 Activity

It is the relative strength of the surface of the stationary phase in adsorption chromatography. In the case of silica gel, the more silanol groups are available on the surface, the more active it is.…

6 Add 10 micro molar EDTA to mobile phase for better peak shapes.

Metals from glass bottles and vials or your instrument can be one cause of poor peak shapes for the polyprotic acids and nucleotides in LCMS. This varies greatly from instrument to instrument so you should…

7 Adjusted retention time

Adjusted retention time (tR') is the retention time adjusted for the hold-up time: tR' = tR - tM where tR is the retention time and tM is the hold-up time. The hold-up time is the time of an analyte (small…

8 Amide vs. Amine/Amino HPLC columns

The amide functional group should not be confused with the amine or amino moiety. The presence of the carbonyl group imparts the amide functionality with significant physical and chemical differences…

9 Analysis of Cysteine by LC-MS

Cysteine is difficult to analyze by LC-MS because it is hard to ionize and also very sensitive to any metals in the instrument such as tubing, injectors, seals, joints etc. We do not currently have an…

10 ANP v. HILIC in Ballistic Gradients.

In comparing ANP vs. HILIC, the former has an advantage in using ballistic gradients because HILIC is generally not suitable for these types of gradients. The reason is the semi-permanent water layer…

11 Aqueous Normal phase (ANP) defined & compared to Reversed Phase & Normal Phase in HPLC

Aqueous Normal Phase (ANP) is probably the newest HPLC technique or at least the latest to be investigated well. Often we are asked what is ANP. Below is a link with more explanation than this article…

12 Aqueous Normal Phase (ANP) retention mechanism elucidated

The mechanism of aqueous normal phase (ANP) retention is an active area of investigation. However, much progress has been made in recent years at elucidating how polar compounds are retained by this mechanism…

13 Assuring retention of polar compounds in an ANP gradient in positive mode LCMS.

When using a Cogent Diamond Hydride™ column prepare your solvents for positive ionization in LC-MS: Solvent A: 50% methanol/50% DI water + 0.1% formic acid and Solvent B: 90% acetonitrile/10% DI water/0.1%…

14 Asymmetry factor

Measure the left half of the peak width at 10% peak height (A) and then measure the right half of the peak width at 10% peak height (B) (see figure below). The ratio of B over A is the asymmetry factor.…

15 Autoclaving inserts with plastic feet is not recommended.

Autoclaving glass or plastic inserts with attached plastic springs is not recommended. While the glass can withstand temperatures up to 1,000°F, the polyetheylene spring will become deformed, may crack…

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