Archive for the ‘GC Injection Techniques’ Category

GC Inlet Liner Selection, Part I: Splitless Liner Selection

Splitless injections are used when detection of trace amounts of analytes is necessary and the goal is to recover close to 100% of all analytes that are injected into the instrument.  During a splitless injection, the split vent is closed for a predetermined amount of time, directing all inlet flow onto the column (with the […]

GC Inlet Liner Selection: An Introduction

GC inlet liners play an important role in GC sample introduction. The sample’s first contact is with the liner and from there it is transferred to the analytical column. In the case of liquid injections, the sample must be vaporized inside of the liner prior to transfer.  Choosing a proper inlet liner for your analysis […]

Trade in Splitless for Split: Faster Speed & More Miles Analyzing 3-MCPD / Glycidyl esters

In my recent work with analysis of 3-MCPD and glycidyl esters, I reviewed the available methods by AOCS and they list splitless or pulsed splitless injection. Splitless injection theoretically transfers all of the sample onto the column, allowing the analyst to achieve trace levels of detection. However, there are limitations. Both splitless hold-time and focusing […]

General (very general) guidelines to help meet GC detection limits.

Sometimes we (tech service) receive requests from customers who cannot meet detection limits when developing a new method or when trying to follow a current method. They ask for advice on how to meet these limits.  As a result, I decided to provide some (very) general guidelines that I would follow back-in-the-day when I would […]

Troubleshooting Injection Volume Variation in the Concurrent Solvent Recondensation – Large Volume Sample Injection Technique

I’ve started receiving a number of questions about the large volume injection technique called Concurrent Solvent Recondensation – Large Volume Sample Injection. Most recently, a question came through the Tech Service group about injection volume variation. I had encountered a similar problem when working on the 50 µL injection for the combined 1,4-Dioxane and Nitrosamines (EPA […]

An introduction to the benefits of using split injection when performing semivolatiles analysis by 8270D – the instrument checkout mix

This blog is part of a series; the previous installments can be found here and here. We have mentioned several times that the reduced residence time resulting from the fast sample transfer that occurs during a split injection reduces in-inlet degradation and adsorptive loss. Proof of this can be seen in the first run of […]

It May be Hot Outside, but Your Headspace Analysis Can Still Suffer from the Cold

Summer days are my favorite – hot, sunny, and full of fun. But one thing that’s really not fun is trying to track down contamination and/or carryover in your headspace-GC (HS-GC) system. I get questions about this topic pretty regularly, so I thought I would post a blog on the most common culprit for contamination […]

Shoot-and-Dilute GC – The exciting world of split ratio

OK, maybe it’s too much to hope that split ratio is exciting, but I think the information I’m laying down, all based on data I’ve recently collected in the lab, can be helpful to anyone working with GC. So please check out my recent article in The Column. Let me know if you have any […]

Split Injection Makes for Easier Polar Solvent GC Work versus Splitless Injection

As anyone who’s doing QuEChERS knows, analyzing acetonitrile extracts on nonpolar GC columns (like Rxi-5ms, e.g.) using splitless injection can be problematic because of the classic solvent – stationary phase mismatch.  To avoid split peaks we usually have an initial GC oven temperature slightly above the 82°C boiling point of acetonitrile (MeCN), but this causes tailing […]

Don’t Forget to Change Your GC Inlet Bottom Seal and Trim Your GC Column as Part of Your Maintenance Routine!

While doing PAH analysis for dirty samples with splitless GC I saw increased peak tailing and loss of response, so I did what anybody would do: changed my GC inlet liner.  In this case I used a Restek Premium single taper inlet liner with wool.  Unfortunately when I did my next standard analysis, not much was improved.  […]