Environmental Express HotBlock CURRENT - Manual (Page 24)

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HotBlock™: Operation and Instruction Manual Adaptation of EPA Methods 245.1, 7470, 7471
4.0 Procedure, Soil, Oil and Sediments, 7471A:
4.1 Weigh 0.25-0.30g of homogenized sample into a tube. For best results,
weigh the sample directly in the vessel on a tared balance.
4.2 Add 5mL DI water and 5mL aqua regia.
4.3 Heat for 2 minutes at 95 ±3°C.
4.4 Allow samples to cool and add 25mL DI water.
4.5 Add 7.5mL of KMnO
4
and let stand for 15 minutes. If sample does not
maintain purple or brown color, add additional portions to all samples,
blanks and standards until the color persists for at least 15 minutes. Heat
samples at 95 ±3°C for 30 minutes.
Note: When using a watch glass, adjust the set point temperature of the HotBlock™ so
that a 50mL sample is heated to 85°C BEFORE placing the watch glass over the sample.
Laboratory tests have proven that the addition of the ribbed watch glass will add 10°C to
the sample temperature, bringing the sample temperature up to 95°C. Refer to page 7 of
the operations manual for instructions on HotBlock™ temperature adjustment.
4.6 Let samples cool to room temperature and add 3mL of Sodium
Choloride-Hydroxylamine Sulfate solution.
All QC samples, concentration limitations, elemental lists and reagent specifications
are addressed in depth in EPA Methods 245.1, 7470 and 7471. Safety concerns are
also part of the EPA Methods. These steps should only be used as a guide to help
improve the performance of your HotBlock™.