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Standard Operating Procedure
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Read the EH&S Standard Operating Procedures Fact Sheet before filling out this form.
Print out the completed SOP and keep a readily accessible hard copy in the lab (also
keeping an electronic copy is highly recommended).
______________________________________________________
Date:
SOP Title:
Using Aqua Regia to remove gold
Principal Investigator:
Room and Building:
Lab Phone Number:
Section 1 – Process
Aqua regia is used to remove gold from substrates. It is a 1:3 mixture of concentrated nitric acid and
concentrated hydrochloric acid and is extremely corrosive. Gold coated atomic force microscope
cantilevers are immersed in a 40 ml solution of aqua regia for a few seconds and then are rinsed in DI
water.
Section 2 – Hazardous Chemicals
Nitric acid
Hydrochloric acid
Section 3 – Potential Hazards
HIGHLY CORROSIVE
STRONG OXIDIZER - May ignite flammable/combustible materials: DO NOT mix with ORGANIC
solvents
OVERPRESSURE EXPLOSION HAZARD – DO NOT confine while reaction continues to out-gas
INHALATION HAZARD – perform work inside a fume hood
Review MSDS before using material, Review EH&S corrosive fact sheet.
Section 4 – Approvals Required
Use of aqua regia must be approved by the Principal Investigator or Lab Safety Officer
Section 5 – Designated Area
Inside chemical fume hood
Section 6 – Special Handling Procedures and Storage
Requirements
Aqua regia waste must be picked up by EH&S. In the mean time, store waste in own glass bottle with
secondary containment in acid chemical fume hood with the cap LOOSELY on top. The solution will
give off gas and could build up pressure if cap were sealed tightly. When waste container is full
dispose of through EH&S.
Whenever handling aqua regia, only use glass containers (preferably Pyrex). Containers used during
the experiment must be very clearly labeled and a warning sign, visible by any user working under the
flow hood, must be posted at all time to indicate that the solutions contains aqua regia mixture.
Mix the solution in the fume hood with the sash between you and the solution. Wear the full
protection.
Section 7 – Personal Protective Equipment
The handling of aqua regia solutions requires special protection equipment in addition to the regular
Clean Room protection outfit (safety goggles, lab coat, gloves).
The additional protective equipment include: a full face shield, heavy duty rubber gloves (regular
disposable Nitrile gloves will not provide sufficient protection), as well as an acid apron to wear on
top of the lab coat.
As a reminder, open-toed shoes are not allowed when working in the lab. Feet and legs must be
covered.
Section 8 – Engineering/Ventilation Controls
Make sure sash is down to create sufficient ventilation. Know that emergency eyewash is working
properly and that it is accessible. Do not dip gloved hands into solution use tools (i.e.. forceps)
Section 9 – Spill and Accident Procedures
In case of large exposure, the victim should be removed from the contaminated area, placed under a
safety shower while emergency personal is contacted(911)
All contaminated clothing should be removed immediately with appropriate gloves and safely
discarded.
In case of contact with the skin, the affected area must be immediately rinsed with large amounts of
water for at least 15min.
In case of contact with the eye, irrigate the eye for at least 30 minutes, keeping the eyelids apart and
away from eyeballs during irrigation. Call 911, Place ice pack on eyes until reaching emergency room.
In case of inhalation, it may irritate the respiratory tract. Conscious persons should be assisted to an
area with fresh, uncontaminated air. Seek medical attention in the event of respiratory irritation,
cough, or tightness in the chest. Symptoms may be delayed.
Section 10 – Waste Disposal
The primary hazard from storage of aqua regia etch waste is the potential for gas generation and over
pressurization of the container when the solution is still hot. If you store a hot solution in a tight
container, it will explode and spray acid!
Therefore prior to store the aqua regia solution, it must be left in an open container in order to cool
down for several hours (overnight). It is your responsibility to make sure that the open container is
very clearly labeled and left in a safe area for overnight cool down.
Once cooled down, the solution can be transferred into a closed glass container for waste storage. The
container must be very clearly labeled with the solution name and composition and must include
VERY VISIBLE warning signs not to add any other types of chemicals.
Never add organic solvents to strong acids.
Section 11 - Decontamination
Rinse contaminated beakers and glassware with lots of water. Carefully pour the aqua regia solution
into the aqua regia waste beaker in the aqua regia hood. Clean area with soap and water, test area with
pH paper, until surfaces are almost neutral.
Section 12 – Process Steps
Process Steps
1. Place on glass slide.
2. In hood, pour 30ml hydrochloric acid in
beaker.
3. Add 10ml nitric acid & swirl gently
4. Take levers on slide in one hand, & using
Safety Measures
Will fume. Keep at least 6” in from edge of fume
hood
tweezers in other hand to lower levers into
beaker (watch orientation – don’t smash
levers on bottom) & tap tweezers between
levers.
5. Let sit for the required time (room temp). Put
sign up on hood. “Agua Regia in Use”
6. Rinse tweezers in lots of water.
7. Rinse & dispose of slide.
8. Fill 2 1000ml beakers with ~800ml DI water
and one 100ml beaker with ~100ml DI
water. Pickup chip (make sure you have a
good grip!) & swirl gently for ~15 seconds in
each of the large beakers. Then place in
smaller beaker.
9. Repeat step 9 for all chips.
10. Dry on cleaned slide. Tap gently (non lever
side!) to remove water and then leave under
scope with light on.
11. Check levers to see if chip is usable (all
there? Cracked?). Store in dessicator.
12. Clean up: Clear out sink. Rinse the “rinse
DO NOT tighten the cap!
beakers” with lots of water. Carefully pour
the aqua regia solution into the aqua regia
waste beaker in the chemical hood. Transfer
to waste bottle when sure the reaction is
done. Cap bottle before pick-up by EH&S,
consider use of a vented cap.
Training Documentation
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