Customers occasionally ask about the hydrocarbon ranges of the Polywax materials which we sell. Although these ranges can vary, the approximate values for each material are found below.
Polywax 500: C20-C72
Polywax 655: C20-C100
Polywax 850: C20-C110
Polywax 1000: C20-C120
Personally, I have never prepared solutions using these materials, so I used Google to try and find information to share with our blog readers. To my surprise, I wasn’t able to find any recommended procedure on the preparation of calibration standards using these Polywax materials. As a result, I needed to ask a few of my coworkers for suggestions/advice. I also reviewed ASTM D7169-11 “Standard Test Method for Boiling Point Distribution of Samples with Residues Such as Crude Oils and Atmospheric and Vacuum Residues by High Temperature Gas Chromatography” to see how the authors of this method recommend preparation of calibration standards.
Below are a few comments/suggestions which you may find helpful if you do not have a method available.
A common dilution solvent is Carbon Disulfide (CS2). Please note that this is a very flammable and toxic material. Always keep the temperature of this solvent below its boiling point when preparing any solution. In addition, always work under a fume hood, and wear protective gear. Section 8 (Reagents and Materials) in ASTM D7169-11 describes how to prepare calibration standards of Polywax 655 / Polywax 1000 using carbon disulfide as the solvent.
For those of you who would rather prepare their solutions with a less dangerous solvent, you may want to try using cyclohexane, or a mixture of cyclohexane/toluene/isooctane. Note that if using GC/FID and a simulated distillation GC column like shown below, the solvent peak may overlap peaks of interest.
Preparation of concentrations above 1% weight/volume can be difficult. The solution is ready for use only if clear. Warming and/or stirring may be necessary (please take all the necessary precautions described above).
Up to 2% w/v may be possible, but customers have reported extreme difficulty in obtaining a clear solution at this concentration.
We generally recommend using Mininert Sampling Valves for standard storage instead of other caps/septa. (Vials)
For additional information about these materials, see Polywax Polyethylenes.
(POLYWAX is a trademark of Baker Hughes Incorporated.)
To read more about Restek individually tested simulated distillation columns, see MXT-1HT SimDist columns.