Excellent inertness for analysis of challenging polar compounds

Yun Zou, Agilent GC Columns Applications

GC and GC/MS detector technology now pushes the limits of detection to the parts-per-billion and parts-per-trillion levels. As these detectors can only detect the analytes that reach them, the activity of the flow path plays a critical role in GC and GC/MS analysis outcomes. Active sites within the flow path can adsorb or catalytically decompose labile analytes, which causes peak tailing and signal loss. The Agilent J&W Ultra Inert GC column family pushes industry standards for consistent column inertness, resulting in lower detection limits and more accurate data for difficult analytes.

Performance tested against the strictest QC standards

New Agilent J&W DB-WAX Ultra Inert columns overcome the persistent inertness problems of standard polyethylene glycol (PEG) columns. All DB-WAX Ultra Inert columns are individually tested with an Ultra Inert Wax test probe mixture according to the strictest industry QC standards. This ensures consistent column-to-column inertness performance for challenging active analytes such as free fatty acids, alcohols, diols, and aldehydes—with minimal compound adsorption or degradation. Having the same selectivity as the Agilent J&W DB-WAX GC column makes upgrading to Ultra Inert performance easy with minimal validation.

Three new Agilent application notes, 5991-6637EN, 5991-6635EN and 5991-6638EN confirm the excellent inertness performance of Agilent J&W DB-WAX Ultra Inert columns.

Figure 1. Chromatograms of a 0.1 mg/mL test mixture of DEG, 1,2-Propanediol, Ethlyene Glycol (EG), 1,3,-Propanediol and glycerin, resolved on an Agilent J&W DB-WAX UI and a WAX column from supplier A.

Figure 2. Chromatograms of a 0.1 mg/mL test mixture of DEG, 1,2-Propanediol, Ethlyene Glycol (EG), 1,3,-Propanediol and glycerin, resolved on an Agilent DB-WAX UI and a WAX column from supplier B.

Figure 3. Overlay of a section the GC/MS chromatogram of lavender oil. Agilent J&W DB WAX (blue) and Agilent J&W DB-WAX UI 30 m x 0.25 m, 0.25 µm (red). Showing that highly active compounds such as terpinen-4-ol (peak 26) and α-terpineol (peak 30) exhibit excellent peak shape and better response on the DB-WAX UI GC column.

Figure 4. Overlaid GC/FID chromatograms of repeat injections of the Chinese liquor sample. Alcohol, aldehyde and organic acid peaks are sharp and well-defined.

Improved and more reproducible peak shapes

Agilent J&W DB-WAX Ultra Inert (UI) columns were used for a GC/MSD analysis of organic solvents— ethylene glycol (EG) and diethylene glycol (DEG)—in toothpaste. The multiple active hydroxyl functional groups found in those compounds make it difficult to achieve good peak shapes during its analysis. Figure 1 demonstrates that when using an Agilent J&W DB-WAX UI column, symmetrical peak shapes were achieved for highly active compounds, including EG and DEG—indicating a high level of column inertness. We compared the performance of the Agilent J&W DB-WAX UI column with other vendor’s WAX columns. Figures 1 and 2 show that good performance was achieved in the first analysis on each WAX column, with the performance of the supplier A and B columns being similar to that of the Agilent J&W DB-WAX UI column. However after 10 injections, there was noticeable tailing and reduced response of 1,3-propanediol in the chromatograms for supplier A and B columns. In contrast, high inertness and improved thermal longevity of the Agilent J&W DB-WAX UI column provided better peak shape and more reproducible analytical results for these active compounds.

Consistent selectivity with improved sensitivity

In another study, lavender oil samples were evaluated using GC-FID and GC/MS. Thirty-six major components of the lavender oil samples were identified. The same selectivity was achieved with both Agilent J&W DB-WAX and J&W DB-WAX UI columns, as illustrated in Figure 3. However the Agilent J&W DB-WAX UI column provided better peak shape and improved sensitivity for active compounds because of its improved inertness. Due to the same selectivity, no additional method development or validation is needed when switching to an Agilent J&W DB-WAX UI column to replace a DB-WAX column.

Excellent performance with challenging samples

A third study included the analysis of distilled spirits. This analysis was challenging because of the high levels of water in the samples (40-80%). Traditional PEG columns had shortcomings with more chemically active components in the alcohol/water matrix and were unstable with aqueous samples. The inertness of the Agilent J&W DB-WAX UI column ensured that excellent resolution and peak shape was achieved for challenging polar compounds, including alcohols, aldehydes and organic acids. Figure 4 shows the overlaid FID chromatograms of 200 injections of Chinese liquor sample on the Agilent J&W DB-WAX UI column, illustrating the excellent reproducibility in retention time and peak shape--overcoming many of the traditional shortcomings of PEG columns.

Ensure better results with Agilent Inert flow path solutions

Agilent J&W DB-WAX Ultra Inert GC columns deliver excellent inertness with more reliable peak shape and better longevity than competitive WAX columns. By minimizing activity along every step of the GC and GC/MS flow path Agilent Inert Flow Path Solutions improve system performance, ensure better results and allow you to process more samples without unplanned maintenance and recalibration. To learn more, watch our video A View of the Inert Flow Path.

For Research and Quality Control Use Only. Not for use in diagnostic procedures.

This information is subject to change without notice.

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Article Directory – June 2016