Two separate cylinder mixes are required by the laboratory for the preparation and analysis of HDS™ Personal Monitors.
HDS™ Preparation: A cylinder containing 1 PPM Bromofluorotoluene (BFT) in Helium is used to “charge” the samplers prior to sending them into the field. Since the BFT remains at the same concentration through the sampling process and delivery back to the laboratory, the BFT serves as an excellent recovery standard to validate leak-tight and inert conditions.
HDS™ Analysis: A second cylinder containing Fluorobenzene (FB) in Nitrogen at 1 PPM is used as an internal standard. Each HDS™ Personal Monitor is pressurized to 7psig (7psi above atmospheric pressure) either manually or automatically on the Entech 7650-L10, 7410D, or 7200 | 7650-M MillionAir™ System, providing an internal standard to verify the correct delivery of the sample to the GCMS.
The Helium/BFT standard utilizes a single stage high purity regulator, while the N2/FB cylinder uses a 2-stage high purity regulator to maintain a more constant 7psig to improve analytical precision. Lower concentration BFT and FB at 10 PPB are used when performing HDS™ sampling in larger canisters and Bottle-Vacs™ for high sensitivity measurements to low or sub-PPB levels.