Agilent J&W Ultra Inert GC Columns: A New Tool to Battle Challenging Active Analytes

John J. Harland, Agilent Technologies, Inc.

QC test probes serve a vital function in ensuring the reproducibility of modern GC columns. These probes ensure that the columns have been properly deactivated, contain the correct amount of stationary phase, and have the same relative retention as the last column purchased. The choice of individual compounds in these test mixes varies widely and can have profound consequences on the performance of a column in the users' applications.

Figure 1

The choice of test probes can either highlight or mask the deficiencies of a column with respect to activity. By selecting undemanding probes, column activity can go undetected.

A QC Test for Today's Demanding Applications

One way of quickly evaluating the suitability of a chromatographic system and column is the deliberate injection of challenging analyte mixes. Good sample recoveries and peak shapes quickly show that the injection system is functioning properly and establish a baseline inertness profile for the column. The baseline inertness profile then serves as a predictor for successful analysis of chemically active species. The use of more demanding test mixes to certify column inertness performance is the approach taken for every column offered in the Agilent J&W Ultra Inert series of capillary GC columns.

Figure 1 shows a baseline inertness chromatogram for an Agilent J&W DB-5ms Ultra Inert column — using the "über One" test mix, the test mix used for every column that is shipped. The probes in this mix have low molecular weights, low boiling points and no steric shielding of their active groups.These characteristics allow the probative portion of the test molecules to penetrate — and fully interact with — the stationary phase and column surface.

The chromatogram illustrates exceptional peak shapes and signal-to-noise ratios, and minimum compound adsorption for these challenging analytes, particularly trimethyl phosphate (#6). The degree of peak tailing for this analyte provides a clear indication of column inertness. On a lesser inert column this peak may not be seen at all.

Testing of each column with the new über One test mix will ensure consistent column inertness. With an established inertness baseline for each column, more demanding analytes can be done routinely.

Conclusions

Today's demanding analysis of trace, active analytes demands the most inert columns available. Unfortunately, not all QC test mixes are capable of differentiating which columns will meet these requirements. With Agilent's new über One Mix, carefully selected chemical species known to adsorb onto active surfaces provide the means for an in-depth evaluation of column inertness.

Each Agilent J&W Ultra Inert column is individually tested with the new über One Mix.This testing provides analysts assurance of consistent column inertness performance, and hence the utmost confidence in their analytical results.

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