Sorbent Properties
Purity
HydrophobU is a carbonaceous sorbent with a purity of over 99.9%. It has negligible sulfur content, and metal impurities can be reduced to levels below 100 ppm, if desired. The high purity ensures efficient release/desorption of analytes of interest. HydrophobU has almost zero ash content and burns completely in air at 650oC.
| Carbon | greater than 99 wt.% |
| Metals | less than 100 ppm |
| Halogens | less than 100 ppm |
| Other elements | less than 10 ppm |
Thermal stability
HydrophobU offers excellent thermal stability with a service temperature of up to 400oC. The higher service temperature of HydrophobU compared to conventional sorbents allows analytes to be released over a shorter timescale, for improved peak shape and resolution. Furthermore, rapid release of analytes allows the use of a low flow rate of the carrier gas. In addition, HydrophobU has high particle endurance (low friability), ensuring a long service life in applications where it is subject to mechanical wear.
Hydrophobicity
In many trace analytical applications, moisture sorption limits the choice of sorbent used. When atmospheric moisture binds to the sorbent surface, it blocks the sorption of analytes of interest, i.e. volatile and semi-volatile organic compounds (VOCs and SVOCs). In contrast to other porous carbon sorbents, HydrophobU is highly hydrophobic while maintaining the ability to adsorb and release a wide or narrow range of VOCs depending on the specific material chosen. The figure on the right shows the moisture sorption of the sorbent material. The material only adsorbs 20 wt.% of water after extended exposure to high relative humidity conditions (70%).
Friability refers to the ease with which a solid substance can be broken up into smaller particles. Most carbon-based sorbents are extremely friable. This means that one must take great care when packing and hauling these sorbents. By contrast, HydrophobU has low friability, i.e. good mechanical integrity. This directly translates to improved anti-clogging properties. HydrophobU does not leave any fines behind when it is placed onto and then removed from a sheet of paper, in contrast to the activated carbon sorbents which leave behind a fine powder, darkening the paper.
