Environmental Express HotBlock Pro - Manual (Page 21)

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HotBlock™: Operation and Instruction Manual EPA Method 200.7
5. Using the polycarbonate transfer racks, remove samples from the HotBlock™ and allow them to cool completely.
6. Bring sample volume to 50mL with DI water.
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 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.
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™.
Adaptation of EPA Method 200.7, Revision 4.4
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 200.7 for use with the Environmental
Express HotBlock™. EPA Method 200.7 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 200.7 for reference while following the sample preparation steps outlined below. A complete list of elements
appropriate for analysis is included in EPA Method 200.7. Analysis can be performed by ICP.
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, Total Recoverable Elements, Aqueous Sample (EPA Method 200.7, Paragraph 11.2):
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 1.5mL concentrated HNO3 and swirl. Heat in the HotBlock™ at a sample temperature of 95°C and evaporate to near
dryness (5mL) taking care that the cup does not go dry. This will take approximately four hours.
3. Using the polycarbonate transfer racks, remove samples from the HotBlock™ and allow them to cool.
4. Add an additional 2.5mL of concentrated HNO3. Cover with a disposable watch glass (catalog number SC505) and
reflux until digestion is complete.
Note: When using a watch glass, adjust the set 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 temperature, bringing the sample temperature up to 95°C. Refer to page 7 of the operations
manual for instructions on HotBlock™ temperature adjustment.
4. Reduce volume to 5mL and cool.