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Agilent J&W Ultra Inert GC columns prove their superiority for analysis of basic compounds
By Judy Berry, Ken Lynam, Caroline Cai, and Yun Zou
Agilent GC Applications Chemists
Analytes with active functional groups (e.g., basic compounds) have historically posed a challenge for GC because they tend to interact with active sites along the GC flow path (e.g., column surface if a GC column is not inert), resulting in peak tailing or irreversible adsorption. These interactions reduce sensitivity and make it difficult to obtain reliable peak identification and quantification. Agilent J&W DB-5ms Ultra Inert capillary GC columns have a special surface treatment that overcomes these problems, and recent experiments clearly show that they provide superior performance for difficult-to-chromatograph basic compounds.
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Table 1. Basic test mixture in methanol.
Table 2. Chromatographic conditions for basic test mixture.
(Click here to see the tables larger.)
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Excellent peak shapes, for better sensitivity and quantification
To measure the inertness performance of various GC columns, we analyzed a group of active basic compounds (Table 1) on DB-5ms UItra Inert columns (30 m x 0.25 mm x 0.25 µm, Agilent p/n 122-5532UI) and columns of the same chemistry (Varian VF-5ms, Restek Rxi-5Sil MS, Phenomenex Zebron ZB-5ms, and GL Sciences InertCap 5MS/Sil) and dimensions from four different vendors. We tested two columns from each vendor under identical conditions, as shown in Table 2. Both qualitative (peak shape) and quantitative (tailing factors) data were used to assess the column inertness performance.
As you can see in Figure 1, the Agilent column provided significantly better peak shapes for the basic compounds in the mixture. Better peak shapes translate to better signal-to-noise and more accurate and repeatable quantification.
We also calculated peak tailing using the U.S. Pharmacopeia tailing factor (Tf), which uses the following formula:
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Tf = W5.0 /(Tw x 2)
where:
- Tw = distance between peak front and retention
time of peak, measured at 5% of peak height;
units are the same as used for W5.0
- W5.0 = peak width at 5% of its height
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The closer the tailing factor is to 1.0, the more symmetrical a peak is. The tailing factors for the first four peaks are included in the chromatograms in Figure 2. The DB-5ms Ultra Inert column produced the best tailing factors in each case, and consequently the best shapes for the compounds of interest and therefore the best column inertness performance.
Inert for other active compounds as well
Every DB-5ms UItra Inert column undergoes a rigorous quality control test that ensures reliable results when you analyze challenging active analytes. That means the columns work well for a wide range of active compounds, as shown in Figure 3, in addition to the basic compounds demonstrated in the previous sections.
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Figure 1. Exceptional peak shapes for basic compounds are evident on the Agilent J&W DB-5ms Ultra Inert column. (Click here to see this image larger.)
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Figure 2. Significantly lower Tf values reveal the extraordinary inertness of the Agilent J&W DB-5ms Ultra Inert column. (Click here to see this image larger.)
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Figure 3. The DB-5ms Ultra Inert columns show outstanding peak shapes for chlorophenols, organophosphorous pesticides, and xylene isomers. (Click here to see this image larger.)
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Agilent J&W DB-5ms UItra Inert capillary GC columns provide superior inertness performance compared to similar columns from other vendors. To learn details about this study, please download the Agilent Application Note (5990-4092EN). If you want maximum sensitivity and more accurate and reliable quantification for analysis of active compounds, try these columns, risk-free.
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