Environmental Express HotBlock CURRENT - Manual (Page 23)

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HotBlock™: Operation and Instruction Manual Adaptation of EPA Methods 245.1, 7470, 7471
1.0 Scope and Application
1.1 The following procedures have been written as an aid to EPA Digestion
Methods 245.1, 7470 and 7471 for use with the Environmental Express
HotBlock™. EPA Methods 245.1 and 7470 are for the determination of
mercury in aqueous samples and TCLP extracts. EPA Method 7471 is for
the determination of mercury in soil, oil and sediment. Use the full EPA
Methods for reference while following the sample preparation steps
outlined below.
2.0 Apparatus and Materials
2.1 HotBlock™ for Metals Digestions — Model Numbers SC100, SC150*, or
SC154
2. Polypropylene Digestion Vessels — Catalog # SC475 (or SC490 for use
with HotBlock™ SC150)
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 )
*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, Aqueous Sample Preparation
3.1 Add 20mL of well-mixed sample to a SC475 digestion vessel or 2mL of
TCLP extract and 18mL water.
Note: This is a 10x dilution for instruments that can achieve the detection limit including
the dilution, otherwise digest 20mL of TCLP extract.
3.2 Add 20mL of standard solutions or appropriate amount of standard
spiking solution to give desired concentration when diluted to 20mL.
3.3 Add 0.5mL of concentrated HNO
3
.
3.4 Add 1.0mL of concentrated H
2
SO
4
.
3.5 Mix thoroughly. Add 3mL of 5% 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.
3.6 Add 1.6mL of 5% persulfate solution. Place watch glass or reflux cap
on top of digestion vessel to allow pressure to vent while minimizing
evaporative loss.
3.7 Digest the sample for 2 hours at 95°C.
3.8 Remove samples and let cool to room temperature.
3.9 Add 1.2mL of sodium chloride/hydroxyl amine hydrochloride solution.
Adaptation of EPA Methods for Mercury Digestions 245.1,
7470, 7471, for use with the Environmental Express
HotBlock™ Digestion System
Revised 05.05