Environmental Express HotBlock Pro - Manual (Page 20)

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HotBlock™: Operation and Instruction Manual EPA Method 200.2
Adaptation for EPA Method 200.2, Revision 2.8
for use with the Environmental Express HotBlock™ Digestion System
Revised 05.05
Scope and Application:
The following procedures have been written as an aid to EPA digestion procedure 200.2 for use with the Environmental Express
HotBlock. EPA Method 200.2 is for the determination of total recoverable analytes in groundwater, surface water, drinking water, wastewater
and (with the exception of silica ) in solid samples such as sediment, sludge and soil. Use EPA Method 200.2 for reference while following the
sample preparation steps outlined below. A complete list of elements appropriate for analysis is included in EPA Method 200.2. Analysis can
be performed by flame atomic absorption, GF/AA, ICP and ICP-MS.
Apparatus and Materials:
1. HotBlock for Metals Digestions — Model Number SC100, SC150* or SC154
2. Polypropylene Digestion Vessels — Part Number SC475 (or SC490 for use with HotBlock SC150)
3. Ribbed Watch Glasses, Part Number SC505 or Reflux Caps, Part Number SC506
(for use with SC490 vials for HotBlock SC150, use Ribbed Watch Glasses, Part Number SC610 )
4. FilterMateTM — Part Number SC0401 (or appropriate FilterMate) for sample filtration if necessary
*Note: For all procedures, when using the SC150 block with the SC490 digestion vials with a 100mL sample, double the volume of all reagents and
acids added.
Procedure, Aqueous Sample Preparation:
1. Mix sample thoroughly to achieve homogeneity. For each digestion procedure, transfer a 50mL sample (or appropriate volume for
your lab) into the SC475 polypropylene vessel. For best results, weigh the sample directly in the vessel on a tared balance.
2. Add 1mL (1:1) HNO3 and 1mL (1:1) HCl, then swirl. Heat the sample in the HotBlock at 95°C for 2.5 hours without boiling. Place a
ribbed watch glass (SC505) on top of the digestion vessel.
Note: When using a watch glass, adjust the control point temperature of the HotBlock so that a 50mL, 5% acid solution 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 approximately 10°C to the sample tem-
perature, bringing the sample temperature up to 95°C. Refer to page 7 of the operations manual for instructions on HotBlock temperature adjustment.
3. Using the polycarbonate transfer racks, remove samples from the HotBlock and allow them to cool.
4. After cooling, dilute samples to 50mL with DI Water.
5. If necessary, filter with SC0401 (or appropriate FilterMate) to remove insoluble material.
The filtration step should be performed slowly with little pressure placed on the plunger. If excessive backpressure 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.
Procedure, Solids Sample Preparation:
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.
2. Add 2mL of (1+1) HNO3 and 5mL of (1+4) HCl+DI. Cover with a ribbed watch glass (SC505) or reflux cap (SC506), and place in the Hot-
Block at 95°C. Refer to page 7 of the operations manual for instructions on HotBlock temperature adjustment.
3. Heat sample for 30 minutes.
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% H2O2 to the well-cooled sample. Allow the exothermic reac-
tion 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 H2O2 raises the sample temperature. Boiling should not occur if the tempera-
ture of the HotBlock is lowered.
Note: H2O2 helps aid in the breakdown of high organic compounds in the sample thus creating a more complete digestion.