Liquid Chromatography

Ion suppression in Biological Sample Analysis: You May or May Not See It but It’s There

Interferences exist in every chromatographic analysis whether they are recognized or not. Interferences can be visible in your chromatogram and present themselves as reduced peak area counts, split peaks, shoulders around the peak, or peak...

Understanding Your Sample Preparation Options – Why “Mixing and Matching” Should Be In Your Sample Prep Tool Kit

A successful chromatographic analysis starts with the sample. Sample selection, collection, transportation, preservation, storage, and sampling protocol are all aspects of testing that need to be considered in the context of your analytical...

Food Analysis: What’s Changing and What Are My Sample Prep Options?

While food and beverage imports and exports continue to increase, regulating bodies are taking a greater interest in these activities that can affect public health. Since the early 2000s, worldwide food imports have increased dramatically, as...

When 'Just Enough' is Not Enough — Part II

In the last column, we discussed ‘just enough’ sample preparation techniques, such as filtration, protein precipitation, extraction partitioning, solid-supported liquid extraction and QuEChERS. Now we will discuss when ‘just enough’ is not enough...

Quantitative Accuracy and Sample Preparation: Pre-Preparation Steps to Improve Results

We’ve covered many of the types of sample preparation options available to make samples ready for instrumental analysis by gas or liquid chromatography and mass spectrometry detection. There are techniques such as QuEChERS, liquid-liquid...

Injecting Organic Solvents in Reversed-Phase

A reader wrote me recently asking what would happen if he injected his sample, which came dissolved in hexane, into a reversed-phase mobile phase of methanol-buffer. The first answer is that this is not a good habit, but is it possible? We’ll see.

Column Abuse, I: Does Air Damage the Column?

I recently had an inquiry from a reader of 'HPLC Solutions' that comes up with some regularity in the HPLC troubleshooting classes that I teach: “Will I damage the column by getting air in it?” Let’s consider the possibilities for a moment. One...

Column Abuse 2: Column Storage

A reader asked me if she was in danger of shortening the lifetime of an HPLC column by removing it after each batch of samples and storing it. This also raised the related question about expectations of shorter column lifetimes if the same...

Column Abuse 3: Oops, I Dropped It!

What happens if your favourite HPLC column accidentally rolls off the bench and lands on the concrete floor of the lab? Is it ruined?

Readers Share In-Line Degasser Experiences

After I wrote an article on in-line Degasser (HPLC solutions #72), I immediately received some reader feedback on a specific failure, which was published in 'Failed Degasser' (HPLC solutions #73). Since that time I have been collecting occasional...

Column Blockage

A reader reported a problem blockage of a column packed with one of the newer shell-type packings. The mobile phase A comprises a mixture of 0.1 M KH2PO4, 0.05% triethylamine (TEA), and 150 mg/L EDTA adjusted to pH 7.5 with NaOH. The B-solvent is...

Method Limits

A reader recently emailed me a question that went something like this: “I’m using LC-MS/MS to analyse a biomolecule that I have isolated from tissue by LC-MS/MS. The lowest point on the calibration curve that I prepared is 0.1 µM. All the samples...

Peak Purity

A reader recently asked a question about the use of the peak-purity function of his diode-array UV detector (DAD). The question related to whether or not he could detect the presence of enantiomers, stereoisomers, diastereoisomers, or epimers...

Dwell Differences

The dwell volume comprises all the HPLC system volume between the point the solvents are mixed to the head of the column. For high-pressure-mixing systems, this includes the mixer, connecting tubing, and sample loop. For low-pressure-mixing...

Measuring Dwell Volume

In a previous article (Dwell Differences, HPLC Solutions #85) we saw an example of how the appearance of a chromatogram could change when a gradient method was run on two HPLC systems of differing dwell volume. In this article we’ll look at a...

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