ORC Bench Studies
Preparative Clean Up
· Hydrocarbon fuels & oils, metabolites, biological or food matrix & elemental sulfur are common chromatography interferents. Without clean-up, dilution is required, & the loss of analyte sensitivity may render the data unusable.
· Various types of clean-ups are available from MAI, including GPC (Gel Permeation Chromatography), bench column chromatography, in-a-vial sorption, & chemical treatment.
· Automated clean-up methods are being developed in-house that will allow more diverse, complex procedures.
· Clean-up techniques are best applied to retricted target groups because the specific chemical affinity of the target analytes is the key to the separation process. ‘Basket’ methods such as EPA 8270 have no useful clean-up procedure whereas restricted chemical groups such as PCBs, PNAs and dioxins have very effective clean-ups.
· GPC (EPA 3660) is applied to matrices containing biological (cell material, peptides, proteins, triglycerides, fats/oils) interferents and/or elemental sulfur & combines size exclusion & affinity chromatography. It is not sufficient by itself to clean up natural matrices but can be a useful starting point, especially for time integrated SPMD samples.
· Bench column chromatography (EPA 3600) primarily uses silica gel, alumina or florisil as sorbents in affinity chromatography & requires skilled chemists, well developed techniques & accompanying QC data for effective use.
· Examples of our laboratory separations using bench column chromatography are:
Aliphatic hydrocarbons (C6-C36) from aromatic hydrocarbons (C6-C36) (TPHCWG)
Unsaturated chlorinated compounds from saturated chlorinated compounds
PCBs from hydrocarbons
Polar oxygen & nitrogen bearing compounds from non-polar compounds
· In-a-vial clean-up, typified by EPA 418.1, is more effective than is generally believed, although the choice of solvent is important. An MAI study demonstrated that it is as effective as bench column chromatography in separating short (C8) & long chain (C27) mono-alcohols from pure hydrocarbons when using hexane as the solvent, & it is less subject to error.
· Chemical treatments, such as water washing to separate water soluble from water-insoluble compounds, or acid-permanganate clean-up of PCBs in oils, are generally less effective than bench column chromatography but are inexpensive & have situational applications.
· MAI can perform customer specifed clean-up procedures or develop custom clean-up procedures upon request.
Industrial Process Research & Development