il60-improved-resolution

By: Leonard M. Sidisky, Katherine K. Stenerson, Michael D. Buchanan, Reporter US Volume 33.1

A Case Study Using a 56-Component Industrial Solvent Mix

The SLB®-IL60 gas chromatography (GC) column is based on an ionic liquid stationary phase platform and displays desirable features that existing non-ionic liquid columns do not. This is the second of several Reporter articles which explore various aspects of this column[1].

The variety of analyte-phase interactions possible with the SLB-IL60 column can be leveraged to provide improved separations. This is especially true for complex mixtures comprised of compounds with varying functionality. Polyethylene glycol (PEG) columns rate at 50-52 on our GC Column Polarity Scale, whereas the SLB-IL60 column has a 60 rating. Therefore, the SLB-IL60 column will exhibit ‘wax-like’ selectivity for many compound classes. However, the higher rating (60 compared to 50-52) does create subtle selectivity differences which is advantagous for many applications, such as multi-component industrial solvent mixtures.

The SLB-IL60 column was compared directly to five popular commercially available PEG columns, each from a different manufacturer. All columns were 30 m x 0.25 mm I.D., 0.25 µm dimensions, except the SLB-IL60 column, which has a 0.20 µm film thickness. Table 1 shows the maximum temperature limits for all columns tested. Complete specifications of SLB-IL60 columns are shown in Table 2.

Table 1. Maximum Temperature Limits*
Column
Isothermal °C
Programmed °C
PEG 1
280
280
PEG 2
260
270
PEG 3
250
260
PEG 4
250
260
PEG 5
280
300
SLB-IL60
300
300
* Obtained from paperwork included with commercial columns.

 

Table 2. SLB-IL60 Column Specifications
Application Modified (deactivated) version of SLB-IL59 provides better inertness. Selectivity more polar than PEG/wax phases, resulting in unique elution patterns. Higher maximum temperature than PEG/wax columns (300 °C compared to 270-280 °C). Excellent alternative to existing PEG/wax columns. Also a good GCxGC column choice. Launched in 2012.
USP Code None
Phase Non-bonded; 1,12-Di(tripropylphosphonium)dodecane bis(trifluoromethylsulfonyl)imide
Temp. Limits 35 °C to 300 °C (isothermal or programmed)


Industrial Solvents
A 56-component industrial solvent mix that contained alcohols, aldehydes, aromatics, chlorinated hydrocarbons, esters, ethers, ketones, and nitrogen-containing compounds was analyzed on each column under identical conditions. All five PEG columns produced almost identical chromatography. Figure 1 and Figure 2 show the chromatograms obtained from the PEG 1 and SLB-IL60 columns, respectively. Observations show the SLB-IL60 column provides:

  • An overall quicker analysis (22 minutes compared to 26 minutes)
  • A vastly different elution pattern
  • Resolution of more analytes; three co-elutions (6 compounds total) compared to six co-elutions (12 compounds total)
  • Resolution of a contaminant peak (peak c), suspected to be 2-methylbutyl acetate, from isoamyl acetate (peak 35)

Figure 1. Industrial Solvents on PEG 1

CONDITIONS: column: PEG 1, 30 m x 0.25 mm I.D., 0.25 µm; oven: 40 °C (4 min), 8 °C/min to 200 °C (5 min); inj. temp.: 250 °C; carrier gas: helium, 30 cm/sec; detector: FID, 250 °C; injection: 1 µL, 100:1 split; liner: 4 mm I.D., split/splitless type, single taper wool packed FocusLiner design; sample: 56-component industrial solvent mix, each analyte at 0.2 % (v/v) in pentane

Figure 2. Industrial Solvents on the SLB-IL60

CONDITIONS: column: SLB-IL60, 30 m x 0.25 mm I.D., df 0.20 µm (29505-U); oven: 40 °C (4 min), 8 °C/min to 200 °C (5 min); inj. temp.: 250 °C; carrier gas: helium, 30 cm/sec; detector: FID, 250 °C; injection: 1 µL, 100:1 split; liner: 4 mm I.D., split/splitless type, single taper wool packed, FocusLiner design; sample: 56-component industrial solvent mix, each analyte at 0.2 % (v/v) in pentane


Conclusion
Columns based on polyethylene glycol phase chemistry are widely used for a variety of applications (such as solvents and FAMEs). However, modification of PEG phase chemistry to affect selectivity is very limited. It is advantageous to possess columns with alternative selectivity, because resolution can be greatly affected by selectivity. The SLB-IL60 column is able to undergo many of the same analyte-phase interactions as PEG columns, plus some additional interactions. This results in the SLB-IL60 column being similar enough to PEG columns to make it useful for many of the same applications, but different enough to impart unique selectivity which can be leveraged to change elution patterns and/or improve resolution..

Featured Products
Description Cat. No.
SLB-IL60 GC Columns
15 m x 0.10 mm I.D., 0.08 µm df 29503-U
20 m x 0.18 mm I.D., 0.14 µm df 29504-U
30 m x 0.25 mm I.D., 0.20 µm df 29505-U
60 m x 0.25 mm I.D., 0.20 µm df 29506-U
30 m x 0.32 mm I.D., 0.26 µm df 29508-U
60 m x 0.32 mm I.D., 0.26 µm df 29509-U


References

  1. Sidisky, L.M.; Stenerson, K.K.; Buchanan, M.D. Supleco SLB-IL60 Ionic Liquid GC Coumns; Supelco Reporter 32.2: 29–31.

Trademarks

  • SLB is a registered trademark of Sigma-Aldrich Co. LLC
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