Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:13:p7
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 13 (pt 7/9)
Character Range: 866919–869844

in this method should be reagent grade or higher.

Dichloromethane (DCM) and acetone should be high purity and give no interference peaks by GC-FID.

Anhydrous sodium sulfate may contain plasticisers leached from plastic storage containers;

each batch should be checked before use. A suggested clean-up method is as follows:
    1. Spread the sodium sulfate on a metal tray to a depth of <2 cm.
    2. Ignite in a muffle furnace at 600°C for 1 hour.
    3. Cool and store in a sealed metal or glass container.

Silica (e.g. Merck, Silica Gel 60, 70230 mesh, methods may require a specific mesh size)

Should be appropriately activated to meet the performance requirements of the method. For example, dry at 200–250ºC for 24 hours minimum and store in a desiccator or tightly sealed container. Deactivate by adding an appropriate weight of reagent grade water and mix thoroughly.

Note: degree of deactivation depends on the constitution of the solvent extract to be cleaned up.

Calibration standards
    * The fraction definition standards for this method—and the calibration standards used to quantify the fractions—are nC10, nC16, nC34 and nC40.
    * A calibration verification standard consists of hydrocarbon product dissolved in extraction solvent. Products used as calibration verification mixes should cover the applicable carbon ranges of the method.
    * Freshly made calibration standards should be checked by GCFID against the calibration standards currently being used in the TRH method as a check for any gross error in their preparation.

13.3.5.3     Procedure
    * Weigh a minimum of 10 g of sample into a tared vessel.
    * Add sufficient amount of anhydrous sodium sulfate to permit drying of sample.
    * Add a minimum of 20 mL DCM:acetone (1:1) and extract by end-over-end tumbler for a minimum of 1 hour. Alternative extraction solvent mixes or extraction procedures can be used if results meet method performance criteria.

13.3.5.4     Silica gel clean-up
Quantities of silica gel used will vary with the volume of extract and the suspected concentration of polar substances. The choice of solvent and suitably deactivated silica gel should demonstrate a quantitative recovery of aliphatic and aromatic hydrocarbons of between 70 and 130%. When validating a particular procedure, this should be demonstrated to quantitatively remove a typical surrogate polar compound, for example, palmitic or stearic acid.

The procedure described below is for a dispersive sorbent clean-up. Mini-columns or commercial silica solid phase cartridges (SPC) may also be used if comparable method performance criteria can be met.
    * Exchange an aliquot of sample extract into a suitable solvent for clean-up. For example, a 1:1 DCM:acetone extract should be exchanged into a solvent other than acetone, to allow for removal of polar substances.
    * To the solvent-exchanged extract add an appropriate weight