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New Agilent J&W Ultra-Inert GC Columns revolutionize semivolatile analysis.
By Kenneth Lynam
Agilent GC Applications Chemist
Anyone who works in the environmental industry knows that one of the greatest challenges you face is the need for ever-greater sensitivity, performance and integrity of analytical results when working with active compounds and trace-level samples, or screening for unknown samples.
Whether quantifying waterborne contaminants or analyzing undiluted soil digests, chemists have been finding that standards for column inertness and sensitivity that were more than adequate just a few years ago are no longer adequate for today’s ever-more demanding trace level environmental analysis.
To address the challenge of ever-increasing column inertness performance, Agilent has developed a new series of capillary columns, the Agilent J&W Ultra Inert GC Capillary Columns. These columns are built on a new technology to deliver on the promise of consistent column inertness, and provide:
- the highest degree of column inertness
- exceptionally low column bleed
- improved peak shapes for active compounds
- greater signal-to-noise ratios
- minimum compound loss and degradation
- extended column life and more instrument uptime
- 0.18 mm ID configuration supported for high throughput applications
Proving that these new columns consistently perform as promised, required development of an aggressive testing mix discussed in detail in the article by Walt Jennings, “Addressing concerns in QC tests for GC columns.” This new testing procedure evaluates GC column inertness performance more effectively by using deliberately aggressive probes to thoroughly investigate column inertness quality.
The following tests clearly show the value of establishing a column inertness baseline and extending that baseline inertness profile to a real-world application – US EPA 8270 – with challenging analytes in the semivolatile sample set. These tests make it easy to see the advantage of using the Agilent J&W Ultra Inert Columns for semivolatile analysis.
Baseline inertness profile predicts successful analysis
Injecting challenging analyte mixes on a chromatographic system can be a good way to evaluate that system’s suitability for the test. Good sample recoveries and peak shapes quickly show that the system is functioning properly and establish a baseline inertness profile for the column. This profile then serves as a predictor for the successful analysis of chemically active species such as semivolatiles.
We tested column baseline inertness on an Agilent 6890N GC equipped with an Agilent 7683B autosampler and an FID using a test mix containing 1-propionic acid, 4-picoline, trimethyl phosphate, and 1-heptanol. Figure 1 shows a baseline inertness chromatograph for an Agilent J&W DB-5ms Ultra Inert column. The chromatogram illustrates exceptional peak shapes and signal-to-noise ratios, and minimum compound adsorption for these challenging analytes. Note in particular the peak shape for trimethyl phosphate (# 6). The observable peak tailing for this analyte makes it an excellent tool for evaluating column inertness. On a lesser inert column this peak may not be seen at all.
Column performance evaluated on semivolatile challenging analytes
We continued to evaluate column performance on a semivolatiles mix selected to range in polarity from basic to acidic species, and from very early eluting nitrosamine to late eluting polynuclear aromatic hydrocarbons (PAHs). Figure 2 is a total ion chromatogram of the challenging analyte mix with a 4-ng on-column loading of each component.
One key assessment criterion for US EPA 8270 system suitability is the response factor for 2,4-dinitrophenol and its most closely eluting internal standard acenaphthene-d10. The minimum acceptable average response factor is 0.050 and the typical range is between 0.1 to 0.2. This response tends to decrease at lower concentrations and as the system or standard starts to deteriorate. Figure 2 shows that response factors – at a concentration of 5 µg/mL – were greater than 0.1 for 2,4-dinitrophenol and were greater than 0.2 for 4-nitrophenal. These values indicate excellent column performance at even low standard concentration.
Benzidine recovery is another key indicator of semivolatile analysis inertness performance because it is subject to thermal breakdown in the inlet at injection port temperatures above 260 °C. In this instance, an injection port temperature of 260 °C gave good recoveries for benzidine and was still hot enough for higher molecular weight PAHs to volatize.
Benzidine retains peak shape in broader semivolatile mix
To further assess US EPA 8270, we tested a mix of 93 semivolatile compounds that included a wide diversity of analyte polarities and that had boiling points ranging from N-nitrosodimethylamine to benzo (g,h,i) perlyene. Figure 3 shows the elution and peak shape of highly basic benzidine and its response relative to flouranthene in the nearest eluting peak. Even in this large mix, benzidine gave good relative response and peak shape.
As you can see from the tests performed, columns with well-defined inertness baselines provide a reliable platform for the analyst to begin analysis of semivolatiles. And Agilent J&W Ultra Inert GC Columns allow you to perform trace level analysis of acids, bases, or other active compounds with the utmost confidence thanks to the industry’s highest degree of column inertness and lowest level of column bleed, minimal compound adsorption, and superior column-to-column consistency – backed by the most stringent individual testing in the industry.
To learn more about this study, review Agilent Application Note 5989-8616EN and the in-depth Über One Test Mix article. For information on the new series of Agilent J&W Ultra Inert GC Columns, view our product page or speak to your Agilent Representative.
References:
- K. Lynam, “Semivolatile Analysis Using an Inertness Performance Tested Agilent J&W DB-5ms Ultra Inert Column,” Application Note 5989-8616EN, 2008.
- “Ultra Inert GC Columns: a New Tool from Agilent J&W to Battle Challenging Active Analytes,” Technical Overview 5989-8665EN, 2008.
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