33 FID Bleed Comparison
Following column installation of new columns, conditioning, and the analysis of two test mixes to demonstrate the column and system were working properly, a temperature programmed bleed run was performed. The final temperature used for each column was based on its programmed temperature limit. An overlay of all six chromatograms is displayed in Figure 7. As shown, only the PEG 4 column exhibited a lower FID bleed level than the SLB-IL60, but did so at a final oven temperature that was 40°C lower. The PEG 5 column exhibited the highest FID bleed, which is surprising considering it has a 300°C limit for progammed use.
Conclusions
Ionic liquid GC columns provide advantages in terms of selectivity, maximum temperature and thermal stability to conventional columns of similar polarity. SLB-IL60 offers a slightly different selectivity compared to PEG phases and a higher maximum temperature and lower FID bleed than PEG/ WAX phases.
References
[1.] A. Bethod, et. al., J. Chromatogr. A, (2008), 1184, 6
[2.] D.W. Armstrong, et. al.,
J.Am.Chem.Soc., (2005), 127, 593A.X.
[3.] Zeng, et. al., Anal. Chim. Acta (2013), 803, 166
[4.] C. Cagliero, et. al., J. Chromatogr. A, (2012), 1268, 130
[5.] C. Ragonese, et. al., Anal. Chem., (2011), 83, 7947
[6.] C. Poole, et. al., J. Chromatogr. A, (2014), in press
Figure 7: FID Bleed Chromatograms Conditions
PEG columns: 30 m x 0.25 mm I.D., 0.25 µm
SLB-IL60 column: SLB-IL60, 30 m x 0.25 mm I.D., 0.20 µm (29505-U) oven: 50°C (2 min), 15°C/min to column programmed temperature limit (10 min) inj. temp.: 250°C
carrier gas: helium, 1 mL/min detector: FID, at column programmed temperature limit injection: 1 µL, splitless sample: methylene chloride
Solutions for Low Abundance Compound Analysis
The analysis of low abundance, basic or naturally occurring sensitive compounds presents particular challenges and difficulties for the chromatographer. The surface of even high quality standard glass vials will contain hydroxyl (silanol) groups that will deprotonate in sample diluents (such as water). These deprotonated hydroxyl groups can result in adsorption of basic compounds, changes in sample solution pH and hydrolyzation of susceptible compounds, potentially making some sample components undetectable and quantitation unreliable. Coating or cleaning the glass surface may improve the situation, but does not eliminate it altogether. Reduced Surface Activity (RSA) glass vials from MicroSolv Technology Corporation have been specifically developed for working with low abundance and sensitive analytes. The proprietary manufacturing process used in producing these vials virtually eliminates all silanol (hydroxyl) groups on the glass surface. This in turn minimises any adsorption of analytes to the glass wall, avoiding loss of sample and reducing inconsistent
quantitation. RSA vials have ultra-low levels of surface metal ions, making them an ideal choice for sensitive LC-MS/MS as well as GC-MS analyses. For further information on RSA vials, email Hichrom Limited, Tel: 0118 930 3660, or contact MicroSolv.
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