The Supelco Dioxin Prep system provides a highly efficient means of extracting and isolating dioxins, furans, and PCBs from stack gases, wastewater, soil, food, blood, and milk. The prep system design reduces solvent usage, decreases  sample preparation time by 1-2 days, and results in extraction recoveries greater  than 85%.

The convenient  multi-layer silica gel column is key to the extraction process; seven layers of treated  silica oxidize, reduce, and separate  polar interferences.  The modular glassware and hardware  design makes it convenient  for analysts to select only a few pieces or the entire prep system for their extraction needs.
A vacuum adapter  and a vacuum manifold provide the option of running a single sample or multiple samples at one time, using vacuum or gravity feed.

Multi-layer Silica Gel Dioxin Column

Potential chromatographic interferences  are removed from the sample as it migrates through  the several layers of treated  silica gel. The silver nitrate treated  layer removes sulphur-containing compounds;  whilst two sulphuric acid treated  layers oxidise sample lipids and remove any basic analytes. The potassium hydroxide treated layer removes any acidic sample components. Dioxins, furans, and Multi-layer PCBs pass through  the silica column unretained.
The column design includes an elongated tapered  end that slips inside the dual-layer carbon reversible tube or Florisil micro column, preventing  leakage of solvent and sample as well as contamination of/by the PTFE fittings. For very dirty samples, bulk treated  silica gels and empty glass tubes are available to customise  packings to meet individual sample needs.

Dual-layer Carbon Reversible Tube

Originally developed for the Japanese  market in accordance  with JIS method  K-0311 and K-0312, a unique dual-layer carbon reversible tube isolates and concentrates the non- ortho PCBs, dioxins, and furans with a minimum of hexane and toluene.  Isolation and separation  is based on the two layers of carbon having different affinities for such compounds. Carboxen-1016 provides a low surface area (75 m2/g), whilst Carboxen-1000 has a high surface area (1200 m2/g).
The combination  of the two Carboxen? layers isolate the dioxins, furans, and non-ortho PCBs. Any aliphatic hydrocarbons and the remaining PCBs present in the sample pass completely through the carbon tube into a waste fraction. The carbon tube is then removed and flushed in reverse direction with toluene to collect the dioxins, furans, and
non-ortho  PCBs.

Dioxin  Prep System - Florisil Version

In 1998, the World Health Organization identified 12 polychlorinated  biphenyls (PCBs) that exhibit dioxin-like activities. These WHO-12 PCBs are now included as part of the overall dioxin concentration and should be systematically investigated in industrial emissions. The original Dioxin Sample Prep System (Multi-layer Silica Gel Dioxin Column plus Dual-layer Carbon Reversible Tube) is ideal for the rapid cleanup and isolation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). However the extraction of PCBs can prove more challenging requiring multiple fractionation  steps. As not all the WHO-12 PCBs are non-ortho, some of these compounds of interest will not be retained. These will pass through the carbon tube directly into the waste fraction, resulting in a split of the PCBs into two fractions. To address this issue a “Dioxin Prep System–Florisil Version” was developed in collaboration with Corus Research, Development and Technology, Rotherham,  UK,and Hall Analytical Laboratories, Manchester,  UK.
In this new system, the Dual-Layer Carbon Reversible Tube is replaced with a micro-column (reversible tube) packed with Pre- Activated Florisil. As the sample extract passes through the multilayer silica gel column and onto the Florisil micro-column, the relatively weak retention  of all the PCBs means they can be easily eluted with n-hexane and /or n-hexane /dichloromethane mixtures. The subsequent PCB fraction contains all PCBs and can be further treated  by basic alumina clean-up to remove any saturated hydrocarbons before analyzed by GC/MS. Further elution of the Florisil micro-column with dichloromethane  is used to collect the PCDD/ F fraction. As a result, the new “Dioxin Prep System–Florisil Version” can rapidly separate  PCBs from PCDD/ Fs prior to analysis for simpler quantitative  determination.

For convenience, ampoulised  Pre-Activated Florisil is available for use with the Dioxin Prep System. The Florisil ampoule is snapped open and emptied  into an empty micro-column (reversible tube), 6.35/10 mm O.D. before sample clean up is performed.

How does it compare?  - Extraction Recoveries

The multi-layer silica gel column in series with the dual-layer carbon reversible tube provides extraction recoveries of 85% or better with less than 200 mL of toluene as illustrated in Figure 3. Recoveries of 13C internal standards  ranged from 65% to 95% [n = 3; RSD from 10% to 20%] for the dual layer carbon system. Figure 4 shows how the recoveries compare to previous used method.  An overview on recoveries with the Florisil system is shown below.

Challenged  with a variety of matrices, the Dioxin Prep System -Florisil Version has demonstrated the ability to clean up sample extracts for dioxin (and PCB) analysis from an array of certified reference  materials and inter-calibration samples including sediments  WMS-01 and DX-3, fish tissue WMF-01, and intercalibration samples from
Orebro University, Sweden (2004 and 2005).

A selection of the results is shown in Figure 5 and Tables 4 & 5*. The Dioxin Prep System showed good recoveries and RSDs for Dioxins and PCBs. Recoveries of 13C internal standards ranged from 80% to 87%[n = 4; RSD from 13% to 16%).