The power of GC-MS/MS for trace analysis in matrix.

Dear GC-MS user,

We thought you might be interested in this very short application note that illustrates the advantage of GC-MS/MS over traditional GC-MS.

Quantifying the pesticide Tebuconazol in cabbage with GC-MS/MS using an Evolution-upgraded Agilent GC-MS system

Chromsys introduced the Evolution upgrade in 2006, and since then many labs in Europe, North America and Asia have benefited greatly from the enhanced sensitivity this upgrade brought them. Analytes that were previously very difficult or downright impossible to quantify in matrix now gave clean and sharp peaks using the SRM mode. The Evolution upgrade is available for EI and CI systems.

In this brief application note, we illustrate how a customer who analyzed tebuconazole in green cabbage increased sensitivity using an Evolution-upgraded system. The results are compared to their old SIM method used before the upgrade.

SIM mode (EI)

(See Figure to the left)

Tebuconazole eluted at 11.50 minutes and the four SIM traces (m/z 250, 125, 83, 70) are shown here. Only one was really usable, but the signal to noise was low and any lower concentration would have caused sensitivity issues.

The same sample with MS/MS (SRM in EI mode)

(See Figure to the left)

Using SRM mode, interference was removed and of the four transitions (250>125 @ -18eV; 125>89 @-15eV; 250>129 @-18eV; 150>70 @-15eV), 250>125 @-18eV gave the highest S/N ratio (black trace in the figure to the left).

MRM is the method of choice when it comes to the determination of low limit concentration of pesticide residues in complex ("heavy") matrix since it offers significant improvements in the signal/noise ratio due to the matrix
elimination effect of the MRM.

A little background on MS/MS

A triple quadrupole mass spectrometer (QqQ) links two stages of mass analysis. The first quadrupole mass filter (Q1) pre-selects a precursor ion ("parent ion") which is fragmented by collision with an inert gas in the RF-only collision cell (q2). The resulting product ions ("daughter ion") are subsequently selected by the thirdquadrupole (Q3) mass filter.

Typical applications for the MS/MS technique are doping analysis, forensic science, drug testing, pesticide residues in food, biomarker analysis for oil exploration, dioxin trace analysis, etc. In essence, samples with heavy matrix.

The Evolution is available both as an upgrade to existing Agilent 5973/5975 systems ($79,000) or a full system (with EI or CI) starting at $129,000 including 7890 GC. Discounts are given for educational institutions. Feel free to give us a call at 703-780-1500. We would be happy to discuss the Evolution and send you a quote.

Sincerely,

Ingo Christ
CHROMSYS LLC