Environmental Express HotBlock Pro - Manual (Page 27)

HotBlock™: Operation and Instruction Manual NIOSH Method 7303
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5. Using the polycarbonate transfer racks, remove samples from the HotBlock™ and cool completely (it is very important that
samples are cooled completely).
6. Add 2-5mL DI Water and 0.5mL of 30% H2O2 slowly. Allow an exothermic reaction to occur. Wait 5-10 minutes and place samples
back in the HotBlock™ with the ribbed watch glasses in place. If effervescence starts to occur lift the samples out of the HotBlock™
and allow the reaction to continue. Do not let the samples foam out of the vessel. (Reducing the HotBlock™ display temperature
by 10°C should reduce the effervescence while maintaining the sample temperature).
6. Continue to add 0.5mL of H2O2 until the sample remains unchanged in color (no longer than 30 minutes). Continue heating for a
total of 2 hours.
7. For the analysis of samples for FLAA or ICP-AES, add 5mL concentrated HCl to each sample and cover with a ribbed watch glass
and reflux at 95°C for 15 minutes. GFAA and ICP-MS digestions, skip this step.
8. After cooling, dilute to 50mL with DI Water.
All QC samples, concentration limitations, elemental lists and reagent specifications are addressed in depth in EPA Method 3050B. Safety
concerns are also part of the full method. Follow the instructions listed in EPA Method 3050B. These steps should only be used as a guide to
help improve the performance of your HotBlock™.
Adaptation of NIOSH Method 7303
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 NIOSH Method 7303 for use with the Environmental Express HotBlock™.
Method 7303 is for the preparation of cellulose ester membrane filters commonly used in air sampling devices. Use EPA Method 7303 for
reference while following the sample preparation steps outlined below. A complete list of elements appropriate for analysis is included in
Method 7303. Analysis can be performed by ICP or AA.
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 )
4. FilterMateTM — Part Number SC0401 (or appropriate FilterMate™) for sample filtration if necessary
* Note: When using the SC150 block with the SC490 digestion vials with a 100mL sample, double the volume of all reagents and
acids added.
Procedure, Filter Preparation:
1. Remove filter from cassette holder and fold into quarters taking care not to lose any sample.
2. Place in SC475 digestion vessel and add 1.25mL HCl.
3. Cover with plastic watch glass or reflux cap. Place in HotBlock™ and heat at a sample temperature of 95°C for 15 minutes.
Note: If using the watch glass, adjust the HotBlock™ temperature so that a 50mL, 5% acid solution is heated to 85°C. Laboratory tests
have proven that the addition of the ribbed watch glass will add approximately 10°C to the sample temperature. Refer to page 6 of the
operations manual for instructions on HotBlock™ temperature adjustment.
3. Remove samples from the HotBlock™ and cool for 5 minutes.
4. Remove watch glass and add 1.25mL HNO3. Replace watch glass and return to HotBlock™ at sample temperature of
95°C for 15 minutes.
5. Remove the sample from the HotBlock™ and cool for at least 5 minutes. Discard watch glass.
6. Dilute to 25mL final volume with distilled, deionized type II water.
All QC samples, concentration limitations, elemental lists and reagent specifications are addressed in depth in Method 7303. Safety concerns
are also part of the full method. Follow the instructions listed in Method 7303. These steps should only be used as a guide to help improve
the performance of your HotBlock™.