Liquid Chromatography

Proficiency testing data portal

Merck has introduced our new proficiency testing data entry portal. The new portal, released 2018, can be accessed at Merck-pt.com. The portal has been streamlined to offer speed, ease of use, and data handling. 

The Basics of HILIC

How can we describe the mechanism at the basis of HILIC retention? We will answer this question and give you an insight into the main interactions that govern chromatographic separation in HILIC mode.

Do you HILIC?

Are your analytes eluting close to the void volume of a reversed-phase (RP) column? Do you have problems retaining organic molecules under conventional reversed‑phase liquid chromatography (RPLC) conditions? Have you increased the initial...

Chromatography software to support more HPLC systems

DataApex is pleased to announce that Clarity VA Chromatography Software supporting the Hitachi Chromaster and Primaide HPLC systems is now available in the North American market. This special Clarity version is exclusively available through...

Acid in A and B

I had a follow-up enquiry about one of the recent articles. In 'Why Acid?', I discussed some of the reasons why acids such as formic or trifluoroacetic (TFA) are added to mobile phases for LC-MS work. The reader noted that in Figure 1 of that...

Injection Problems

Q: I am running an isocratic method with a 250 x 4.6 mm, 10 µm particle column at 1 mL/min with a 20% acetonitrile (ACN)/buffer mobile phase. I dissolve my sample in ACN and inject. Normally my compound of interest comes out at 7.7 min. I...

Frit Cleaning

In a recent email, a reader enquired about the best way to clean the frits used in the HPLC system. He indicated that he had been sonicating them in nitric acid, but wasn’t sure if that was the best way to approach the problem.

Retention Shifts

A reader complained about retention times that changed in an overnight HPLC run and wondered how to diagnose the problem source. The question left too many possibilities, and because there was no complaint about changing resolution, I’ll assume...

Enantiomer Separations

Recently, a reader sent a question about how to get started with a method that required separation of enantiomers by reversed-phase HPLC. Unfortunately, the problem is a non-starter in this context. Enantiomers cannot be separated by...

MP Lifetimes

A reader recently sent in this e-mail: “I am trying to find information that I can put in an SOP regarding how long a mobile phase can be used before it must be discarded. I’ve heard 1-2 weeks from some sources, whereas others say a month, and...

Why Acid?

Recently, I received an email from a reader asking why formic acid was specified as an additive for the mobile phase in an HPLC method he was using. Formic or trifluoroacetic acid at 0.1% concentrations are common, especially for LC-MS work....

PEEK Follow-up

PEEK (poly-ether-ether-ketone) tubing and fittings have become a standard part of most HPLC systems today. The flexibility and ease of cutting the tubing, coupled with the convenience of finger-tightened fittings make a combination that is hard...

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