
279572d33ad07a1d64ca043974f39b5b.ppt
- Количество слайдов: 44
Advances in Capillary Columns For Gas Chromatographic Applications Shawn Reese, Roy Lautamo, Chris Cox Gianna Barlupi, Rick Morehead, Jason Thomas, Gary Stidsen, and Frank Dorman
Old Technology? • Gas Chromatography is 50 years old! Like wine and cheese it seems to keep getting better!! • Packed columns (over 100 different phases) • Capillary debut commercially in 1970’s • Phase development parallels some packed column phases
Phase Development – Early Phases
Capillary Phase Technology • Pendant siloxanes do not show large viscosity changes with temperature (from -40 to 400 o. C) • High polarity applications require a wax phase which has a high temperature limit of 260 • Deactivation technology varies from manufacturer and can be a limiting factor on what is possible • Pendant phases are fairly similar from manufacturer to manufacturer
What Does the Industry Need? • Low Bleed? – What is bleed? Can it be stopped? • “MS” Phases? – Application of low-bleed technology? • Reproducible columns? – Why do our manufacturing profiles matter to you? • Inertness – Professor Walt Jennings, Riva 2004 • Selectivity-specific applications – PCB’s, Dioxins, PBDPE’s, pesticides
What is Bleed? • Common bleed ions associated with phases that contain PDMS • La. Chatlier’s principle works against us due to the volatility of the products.
Slowing Down Decomposition • “G” groups spreads Si-O groups out so that they cannot “back -bite” each other and form small cyclic rings.
Bleed Mass Spectrum Scan 3634 (24. 939 min): C 0830013. D 207 Abundance 7000 6500 Pentamethylcyclotrisiloxane+ 6000 5500 5000 4500 Heptamethylcyclotetrasiloxane+ 4000 Trimethylsilyl+ 3500 3000 2500 2000 73 1500 1000 44 281 96 500 0 m/z--> 133 156 50 100 150 177 230 200 253 250 327 355 384 407 430 455 475 300 350 400 450
Backbone modified phases slow down the back-biting mechanism
Low-Bleed – 1 st Generation (90’s) • What drives innovation? Introduction of “ms” phases! • As GC manufacturers make more sensitive detectors demands from the phases increase. • 1 st generation was a “ 5” in the backbone, first produced by Sveda (1951!)…did not appear in GC phases until early 1990’s. • Thermal decomposition decreased due to “stiffining” of the backbone chain.
Low Bleed Next Generation 21 st Century • “Next” Generation was application of “other” backbone modified groups, and “new” pendant groups • Selectivity can vary dramatically if the pendant groups are very different from one another, and the backbone Group “G” is significantly different than “phenyl”.
What “G” groups have been used? • Literature reports the following groups:
Deactivations – A new problem? • Bench-top mass spectrometers in the early 90’s had sensitivity similar to the standard FID • Today, sensitivity of bench-top mass spectrometers are better than the standard FID, and the column can interfere with detection. • Inertness is a more serious issue now with detection below nanogram levels on MS.
What else can we do? • As the mechanism on the previous slide implies, chemically inert polymers demand the most stringent synthetic conditions • We have devised “systems” that limit the polymers ability to “find” proton sources during phase procurement through deactivation techniques and through new, proprietary syntheses.
Restek’s Exceptionally Inert GC Columns (Rxi) • New column technology developed by Chemists at Restek and new research lab, Restek West • Rxi-1 ms, Rxi-5 ms • New deactivation chemistry, new polymer chemistry, new manufacturing process • Results in columns that are: – Highly Inert – Reproducible – Low bleed
Reproducibility = Reliablity for the user! • In-house QC results • Comparison between manufacturers • What do you need?
Bleed of Manufactured Columns Mean = 1. 9 p. A SD = 0. 65
Rxi-5 ms Bleed Study (30 m x 0. 25 mm, 0. 25 um film) Reference Peak 1 ng tridecane Columns include: 5% diphenyl 95% dimethyl & Silarylene based phases (30 m x 0. 25 mm, 0. 25 um) Detector: FID 350 o. C 330 o. C Rxi-5 ms 6 4 2
Retention Time “Windows” Ultimate Reproducibility Column-to-Column • Exact Length – Is this important? • Isothermal testing – Comparison of batch to batch reproducibility • In-house QC results – Film thickness – Coating efficiency – Selectivity
Rxi-5 ms Column Reproducibility
Film Thickness
Coating Efficiency
Selectivity
Selectivity
Inertness • 0. 5 ng on-column concentration – Basic compound – Acidic compound • 2 ng on-column comparison between manufacturers – Chromatographic peaks of pyridine – Response factor • This is the area that is a “WIP”…. we have come a long way…. . can it get better? We’ll show Rxi as an example of what all columns should be like!
Rxi-5 ms Column Inertness (30 m x 0. 25 mm, 0. 25 um) Acidic Compounds m/z 74 m/z 79 m/z 184 Basic Compounds
2 ng Pyridine Rxi-5 ms (30 m x 0. 25 mm, 0. 25 um)
Rxi-5 ms Column Inertness (30 m x 0. 25 mm, 0. 25 um)
Rxi-5 ms Column Inertness (30 m x 0. 25 mm, 0. 25 um)
Inertness Probes
Applications • Environmental – Semivolatile analysis • Clinical – Acidic and basic drugs
Rxi-5 ms Semivolatiles (5 ng on-column)
Rxi-5 ms Semivolatiles (5 ng on-column)
Rxi-5 ms Analysis of Drug Compounds
Rxi-5 ms Analysis of Drug Compounds
Summary of Rxi Columns • Unsurpassed inertness for active compounds • Low bleed • Excellent column to column manufacturing • Excellent overall performance due to combination of inertness, low bleed, and reproducible manufacturing process
Special Selectivity? • Application specific – not everyone is doing congener specific PCB analysis • Utilizes low-bleed technology, and incorporates many manufacturing techniques as our Rxi process • These polymers are Restek specific; cannot be found from other manufacturers
Rtx-Dioxin 2 • New phase that is specially “tuned” for dioxin analysis
Rtx-Dioxin 2
Rtx-PCB Congener Specific Analysis • Resolves most PCB’s into absolute separation or “MS-resolvable” separations (differing Cl numbers). • A low bleed phase – will allow for high temperature applications for “dirty” samples.
Rtx-PCB place picture here
Rtx-5 Sil. Ms – Shape selectivity
Rtx-17 Fused Silica Column • Rtx-50 vs Rtx-17 Rtx-50 – Both 50% phenyl / 50% methyl • Selectivity between Rtx-50 and Rtx-17 is different • GCx. GC separations coupled to a 5 or 1 • Equivalent selectivity to DB-17 Rtx-17
Acknowledgements • Chris English and innovations group for applications • Roy Lautamo for suggestions on how to proceed • Shimadzu for kind invitation and providing support for this trip!!