Environmental Express HotBlock Pro - Manual (Page 24)

HotBlock™: Operation and Instruction Manual EPA Methods for Mercury Digestions
22 • Environmental Express www.environmentalexpress.com / 800.745.8218 / 843.576.1147
Adaptation of EPA Methods for Mercury Digestions 245.1, 7470, 7471,
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 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.
Apparatus and Materials:
1. HotBlock™ for Metals Digestions — Model Numbers 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 )
*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. 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.
2. Add 20mL of standard solutions or appropriate amount of standard spiking solution to give desired concentration when
diluted to 20mL.
3. Add 0.5mL of concentrated HNO3.
4. Add 1.0mL of concentrated H2SO4.
5. Mix thoroughly. Add 3mL of 5% KMnO4 and let stand for 15 minutes. If sample does not maintain purple or brown color, add an
additional 3mL of KMnO4 solution to all samples, blanks and standards. If the sample still does not maintain color, discard set
and dilute the sample prior to digestion.
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.
7. Digest the sample for 2 hours at 95°C ± 5%.
8. Remove samples and let cool to room temperature.
9. Add 1mL of 12% sodium chloride/ hydroxyl amine hydrochloride solution.
Procedure, Soil, Oil and Sediments, 7471A:
1. Add 30mL of each standard solution or appropriate amount of standard spiking solution to give desired concentration when
diluted to 30mL in a SC475 cup. The standards should be made in 3% HNO3.
2. Weigh 0.60± 0.05g of homogenized sample into a tube. For best results, weigh the sample directly in the vessel on
a tared balance.