Environmental Express HotBlock CURRENT - Manual (Page 19)

800.745.8218 / 843.576.1147 / www.environmentalexpress.com Environmental Express • 17
HotBlock™: Operation and Instruction Manual EPA Method 200.7, Revision 4.4
1.0 Scope and Application
1.1 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.
2.0 Apparatus and Materials
2.1 HotBlock™ for Metals Digestions — Model Number SC100, SC150*, or
SC154
2.2 Polypropylene Digestion Vessels — Catalog # SC475 (or SC490 for use
with HotBlock™ SC150)
2.3 Ribbed Watch Glasses, Catalog # SC505 or Reflux Caps, Catalog # SC506
(for use with SC490 vials for HotBlock™ SC150, use Ribbed Watch Glasses,
Catalog # SC610 )
2.4 FilterMate™ — Catalog # 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.
3.0 Procedure, Total Recoverable Elements, Aqueous Sample
(EPA Method 200.7, Paragraph 11.2)
3.1 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.
3.2 Add 1mL 1:1 HNO
3
and 0.5mL 1:1 HCl and swirl. Heat in the HotBlock™
at a sample temperature of 85°C and evaporate to about 10mL taking
care that the cup does not go dry. This will take approximately 2 hours.
3.3 Cover the vessel with a disposable watch glass (catalog # SC505) and
reflux an additional 30 minutes.
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.
3.4 Using the polycarbonate transfer racks, remove samples from the
HotBlock™ and allow them to cool. Bring samples up to volume with DI
water.
Adaptation for EPA Method 200.7, Revision 4.4 for use with the
Environmental Express HotBlock™ Digestion System
Revised 05.05