Avoiding Split Peaks in Gas Chromatography for QuEChERS Extracts in Acetonitrile

Acetonitrile injections don’t damage Rxi-5Sil MS GC columns. But urban legends persist, so analysts sometimes do unnecessary and laborious solvent exchanges for QuEChERS extracts.

A real problem that might warrant solvent exchange is mismatch between the polar solvent acetonitrile and non-polar pesticide GC columns (e.g. DB-5ms, Rxi-5Sil MS). Upon injection, lack of wetting leads to split GC peaks, especially severe for early eluters. Adjusting GC oven start temperatures rarely eliminates the problem.

A simple method for avoiding split GC peaks for acetonitrile extracts is to add toluene to the extract. At 50% toluene, peak splitting is gone, and sensitivity is only reduced by 2 (not even that, considering height reduction of split peaks). Even 25% toluene can eradicate peak splitting. Adding internal standard in toluene to a QuEChERS extract prior to injection is an elegant way to kill two European Starlings with one Accrington brick. And, no solvent exchange!

2 Responses to “Avoiding Split Peaks in Gas Chromatography for QuEChERS Extracts in Acetonitrile”

  1. […] Also Mixing with another solvent, like toluene, may also help, see: Some excellent work was done by Jack Cochran to fix this:   http://blog.restek.com/?p=638 […]

  2. […] 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 […]

Leave a Reply

Restek Domestic Customer Service



Your Full Name

Your Email

Company Name


Spam Block (Please leave this blank)

all fields required

Thank you

Your message has been sent. We will be in touch shortly.

Message not sent

Sorry, your message could not be sent at this time. Please try again later, or contact Restek or your local Restek representative via phone.