In addition to exhibiting, Restek will hold a vendor seminar at the 7th International Symposium on Recent Advances in Food Analysis (RAFA). Presented by Restek’s own Julie Kowalski on November 5 at 1:30 p.m., this valuable seminar will explore prolonging GC-MS/MS performance by means of Shoot-and-Dilute injection versus analyte protectants. Prizes will also be given away to select attendees.
RAFA 2015 takes place on November 3–6, 2015 at the Clarion Congress Hotel Prague, Czech Republic. This biennial symposium summarizes the latest strategies and identifies current issues surrounding food quality and safety control analysis and bioanalysis. While at RAFA, be sure to also stop by Booth# 46 for a visit and to discuss our latest innovations in food science.
Visit http://www.rafa2015.eu/programme_vendors_seminars.html today to register for the symposium and to sign up for Restek’s vendor seminar.
Prolonging GC-MS/MS Performance: Shoot-and-Dilute Injection versus Analyte Protectants
Thursday, November 5, 1:30 p.m.
Julie Kowalski and Jack Cochran
In gas chromatography–mass spectrometry (GC-MS), most problems occur on the front end, at the GC inlet, where compounds can degrade during hot splitless injection, active compounds can be irreversibly adsorbed to inlet liner surfaces, and nonvolatile material from dirty samples can compromise the transfer of less volatile compounds of interest from the inlet to the GC column. These issues are magnified due to the very slow inlet flow during splitless injection, which is typically less than 2 mL/min.
Two strategies to mitigate these issues will be demonstrated in this seminar. One approach is to use split injection, what we call, and “Shoot-and-Dilute.” With newer, more sensitive GC-MS/MS systems, LOD and LOQ requirements are often achievable using split injections at ratios of 10:1 or greater. Increased flow through the inlet during split injection minimizes residence time inside the inlet liner, which decreases compound degradation and adsorption, and maintains acceptable data quality longer. In addition, GC oven start temperature can be higher, thus reducing overall run time as well as the time needed to re-equilibrate the GC oven prior to the next analysis. Another benefit of split injection is improved peak shape for early eluting pesticides when injecting acetonitrile-based QuEChERS extracts.
The second strategy to overcome GC inlet problems is to use “analyte protectants,” which are essentially volatile and chromatograph-able masking agents such as sugars, diols, etc., that are co-injected with each sample and standard to temporarily occupy active sites in the GC inlet liner and column. These analyte protectants have low m/z ions and the mass spectrometer can essentially overlook them in favor of target compounds.
Both strategies were tested with multiclass pesticides and compared against a typical splitless injection method without use of analyte protectants for QuEChERS samples. For Shoot-and-Dilute, viability of split injection based on detectability of a wide range of analytes was determined. Optimized split injection, inlet, and initial GC oven temperatures were determined. Benefits of analyte protectants were evaluated by peak shapes and responses of both well-behaved and problem pesticides. The goal of both Shoot-and-Dilute and analyte protectants approaches is to improve initial and long-term chromatographic performance.