Environmental Express HotBlock CURRENT - Manual (Page 18)

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HotBlock™: Operation and Instruction Manual EPA Method 200.2, Revision 2.8
4.0 Procedure, Solids Sample Preparation
4.1 Sieve a dried sample using a 5-mesh polypropylene sieve and grind in a
mortar and pestle. Weigh a representative sample of 0.5 ±0.01g into a
digestion vessel.
4.2 Add 2mL of (1+1) HNO
3
and 5mL of (1+4) HCl+DI. Cover with a ribbed
watch glass (SC505) or reflux cap (SC506),and place in the HotBlock™
at 95°C. Refer to page 7 of the operations manual for instructions on
HotBlock™ temperature adjustment.
4.3 Heat sample for 30 minutes.
4.4 (Optional) Although step 3 is the final heating step for EPA Method 200.2,
if the sample is suspected of having a high concentration of organic
compounds, it is recommend to complete this step:
Add 2mL of 30% H
2
O
2
to the well-cooled sample. Allow the exothermic
reaction to occur (approximately 10 minutes) and place the sample
back in the HotBlock™ at a temperature of 10° less than the original set
point for an additional 30 minutes. The reaction with the H
2
O
2
raises the
sample temperature. Boiling should not occur if the temperature of the
HotBlock™ is lowered.
Note: H
2
O
2
helps aid in the breakdown of high organic compounds in the sample thus
creating a more complete digestion.
4.5 Using the polycarbonate transfer racks, remove samples from the
HotBlock™ and allow them to cool completely.
4.6 Bring sample volume to 50mL with DI water.
4.7 If necessary, filter with SC0401 (or appropriate FilterMate) to remove
insoluble material.
Note: The filtration step should be performed slowly with little pressure placed on the
plunger. If excessive back pressure occurs, stop filtration and allow sediments to “settle
out”. Applying pressure to the plunger may cause sample “blow through” allowing
sediment to pass through the filter into the digestate.
All QC samples, concentration limitations, elemental lists and reagent
specifications are addressed in depth in EPA Method 200.2. Safety concerns are
also part of the full method. Follow the instructions listed in EPA Method 200.2.
These steps should only be used as a guide to help improve the performance of
your HotBlock™.