CHROMATOGRAPHY 43 glycol ether analysisSPEEDING UP
Rebecca Stevens & Chris English explore how replacing a 624- type column with an Rxi-1301Sil MS column reduces GC analysis time and maintains good separation of glycol ethers of regulatory concern
G
lycol ethers are high production volume industrial chemicals
that often occur as complex mixtures of isomers. Teir unique amphiphilic structure gives them favourable properties such as low volatility, strong solvent strength, high water solubility and the ability to serve as coupling agents that promote the miscibility of aqueous and organic phases. Tese properties make glycol ethers a popular alternative to traditional oxygenated solvents such as ketones, ethers and alcohols. Because toxicological studies indicate that some glycol ethers pose a serious health hazard, the EU and Canada have both adopted regulations limiting their use in consumer products. In the EU, several glycol ethers are banned entirely while others are regulated to a specific concentration level. In 2010, Environment Canada (EC) published a reference method1
for analysis of glycol
ethers in consumer products including cleaners, degreasers and coatings. Te EC method addresses the most commonly used glycol ethers and describes
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an analytical approach for achieving reporting limits.
Column choice is key to faster analysis Te EC method recommends a standard 624-type column in a 60m x 0.32mm x 1.80 µm format and a temperature program that spans 30 minutes for glycol ether analysis. To reduce analysis time, we used an Rxi-1301Sil MS column instead of a 624 column. Te Rxi-1301Sil MS column has very similar selectivity to that of 624-type columns as both are based on cyanopropylphenyl stationary phases; however, the thinner film and higher thermal stability of the Rxi-1301Sil MS column provide good separations in a fraction of the time. Te Rxi-1301Sil MS column
in a 30m x 0.25mm x 0.25 µm format with optimised run conditions results in an analysis time of just eight minutes (Fig. 1). Using a fast temperature program, baseline resolution of the DPGME isomer group is possible and is comparable to – if not better than – the original method. Te 0.25 µm film results in higher efficiency, narrow peaks, and, in turn, improved resolution with less retention. Te Rxi-1301Sil MS column also has a temperature limit of 320°C, allowing for a high- temperature isothermal hold to remove any low-volatility sample components from the column. If these low-volatility contaminants are not removed they may elute in subsequent analyses as broad ‘ghost’ peaks, possibly interfering with the analytes of interest.
Fig. 1. An Rxi-1301Sil MS column provides excellent separation of glycol ethers of regulatory importance three times faster than under the EC method conditions while maintaining baseline resolution of the DPGME isomers
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