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AOAC OFFICIAL METHODS OF ANALYSIS (1995)
This chapter is not intended to be an exhaustive treatise on labora-
tory safety. These precautionary notes serve only as a reminder of
possible hazards involved in the use of particular operations or sub-
stances. Refer to recommended texts at end of chapter for fuller
treatment of subject. Follow safety requirements of those in the
country, region, or jurisdiction within which your organization is sit-
uated. Consult guidelines issued by professional associations and
government agencies.
Cautionary Statements
Nature and amount of each chemical and its prescribed use were
criteria used in determining if cautionary statement for method was
indicated. Safety hazard was considered to exist when nature,
amount, and use of chemical or equipment specified in method ap-
peared likely to produce any of the following:
(a) Concentration of vapors from flammable liquid exceeding
25% of lower flammability limit of that liquid described by National
Fire Protection Association, Boston, MA, USA.
(b) Contact between analyst and amounts of material highly ac-
tive physiologically or toxic to humans in excess of Threshold Limit
Values published by American Conference of Governmental Indus-
trial Hygienists, PO Box 1937, Cincinnati, OH 45201, USA.
(c) Contact between analyst and amounts of highly corrosive ma-
terial sufficient to produce serious injury.
(d) Contact between analyst and radiations which could be harmful.
(e) Explosion or violent reaction.
(f) Injury to analyst by hazards in equipment or processes which
are not readily detectable by analyst.
When in doubt about possible hazards not covered in this chap-
ter, consult references at end of chapter or other sources of infor-
mation such as hazard warnings on labels and manufacturers’
data sheets.
Potential Hazards of Equipment
Refrigerators
Refrigerators should be explosion-proof or explosion-resistant
when used for storage of ether and other highly volatile, flammable
liquids. Ordinary refrigerators can be made explosion resistant by
removal of light switch, receptacle, and associated wiring, and by
placing thermoregulation controls outside of refrigerator.
Glass
Dispose of chipped or broken glassware in special containers; mi-
nor chips may be fire-polished and glassware retained. If glassware
is to be repaired, mark defective area plainly and store in special lo-
cation until repairs are completed.
Use heat-resistant glassware for preparation of solutions that gen-
erate heat (e.g., not bottles or graduated cylinders).
Fire Extinguishers
Class B and C dry chemical fire extinguishers (for flammable liq-
uid and electric fires) should be conveniently available to each labo-
ratory room. Carbon dioxide fire extinguishers should be used on
fires in electronic equipment.
Become familiar with the location of all fire extinguishers and the
appropriate methods for their effective use.
Blenders
Motor on high-speed blenders used to mix flammable solvent
with other materials should be explosion-proof. Blend toxic or flam-
mable liquids in effective fume-removal device.
Centrifuges
Adjust all tubes to equal weight before loading them into cen-
trifuge. Make certain that stoppers of tubes placed in pivot-type
head will clear center when tubes swing to horizontal. Do not
open centrifuge cover until machine stops completely. Before re-
moving tubes, turn electric switch to “off.’’ Do not rely on
zero-set rheostat. Use only tubes specially designed for centrifug-
ing. Do not exceed safe speed for various tube materials (glass,
cellulose nitrate, polyethylene, etc.) recommended by tube manu-
facturer. Cellulose nitrate tubes may explode if autoclaved.
Heating cellulose nitrate tubes to 60°C may cause them to pro-
duce harmful nitrogen oxide fumes.
Atomic Absorption Spectrophotometer
Follow all manufacturer’s instructions for installation, opera-
tion, safety, and maintenance. Use only hose/tubing to conduct
gases that are approved by manufacturer and supplier. Use effec-
tive fume removal device to remove gaseous effluents from
burner. Use only C2H2 which is dissolved in solvent recom-
mended by manufacturer. Open C2H2 tank stem valve only a quar-
ter turn. Change tank when C2H2 pressure shows 75–100 lb. If
instrument has a drain trap, ensure that it is filled with H2O before
igniting burner. Following repair to C2H2 supply line, check for
gas tightness at all connections with soap solution or combustible
gas detection system. When aspirating solutions containing high
concentrations of Cu, Ag, or Hg, spray chamber should be
rinsed with 50–100 mL H2O before shutting down to c l e a n
these metals from chamber. See safety notes on compressed gas
cylinders.
Flame Photometer
Use effective fume removal device to remove gaseous burner
effluents.
Photofluorometer
Considerable amounts of O3 are formed by UV light radiated by
quartz lamp. Ozone is toxic even in low concentrations; remove
through effective fume removal device placed near quartz lamp.
Monitoring Equipment
Monitor unattended operations with equipment that will auto-
matically shut down process if unsafe condition develops.
© 2000 AOAC INTERNATIONAL
Reference: Furr, A.K. (1995) “CRC Handbook of Laboratory
Safety,” CRC Press LLC Headquarters, 2000 NW
Corporate Blvd, Boca Raton, FL 33431, USA.
Compressed Gas Cylinders
Identify by name(s) contents of compressed gas cylinders on at-
tached decal, stencil, or tag, instead of by color codes. Move cylin-
ders (with protective cap) upright, secured to cart. Secure cylinders
in upright position by means of strap, chain, or nontip base. Let con-
tents of C2H2 cylinders settle and let all cylinders come to room tem-
perature prior to opening. Use only correct pressure gages, pressure
regulator, flow regulator, and hose/tubing for each size of gas cylin-
der and type of gas as specified by supplier. Use soap solution or
combustible gas detection system to check all connections, espe-
cially when system is pressurized and gas is not flowing, to check for
slow leak. Use special heater on N2O gas line. Close gas tank valve
and diaphragm on regulator when gas is not in use. Service regulator
at least yearly. Use toxic gases only in effective fume removal device.
When burning gas, use flashback prevention device in gas line on out-
put side of regulator to prevent flame being sucked into cylinder.
Reference: “Handbook of Compressed Gases” (1981) Com-
pressed Gas Association, Van Nostrand Reinhold
Co., New York, NY, USA.
Distillation, Extraction, and Evaporations
(a) Flammable liquids.—Perform operations behind safety barrier
with hot H2O, steam, or electric mantle heating. Use effective fume re-
moval device to remove flammable vapors as produced. Set up appara-
tus on firm supports and secure all connections. Leave ample headroom
in flask and add boiling chips before heating is begun. All controls, un-
less vapor sealed, should be located outside vapor area.
(b) Toxic liquids.—Use effective fume removal device to re-
move toxic vapors as produced. Avoid contact with skin. Set up ap-
paratus on firm supports and secure all connections.
Electrical Equipment
Accidents involving electric equipment may result in mechanical
injury, e.g., fingers being caught in chopping mill knives; electric
shock, which may be due to lack of or improper grounding, defective
equipment, exposed wiring, or inadequate maintenance; and fire
through ignition of flammable vapors by electrically produced
spark. Ground all electric equipment to avoid accidental shock. In-
stallation, maintenance, and repair operations should be performed
by qualified electricians.
Parr Bomb
Follow manufacturer’s directions closely to avoid explosion.
Pressure
Do not conduct pressure operations with standard glassware. In
certain circumstances, glassware specifically designed to withstand
pressure may be used. Observe manufacturer’s recommended
safeguards when using pressure apparatus such as calorimeter
bomb, hydrogenator, etc.
Vacuum
Tape or shield with safety barrier containers and apparatus to be
used under vacuum to minimize effects of possible implosion. Vac-
uum pump drive belts must have effective guards.
© 2000 AOAC INTERNATIONAL
Hazardous Radiations
UV radiation is encountered in AA spectrophotometry, fluorometry,
UV spectrophotometry, germicidal lamps, and both long- and shortwave
UV lamps used to monitor chromatographic separations. Never expose
unprotected eyes to UV light from any source either direct or reflected
(e.g., flames in flame photometer, lamps, electric arcs, etc.). Always wear
appropriate eye protection such as goggles with uranium oxide lenses,
welder’s goggles, etc., when such radiations are present and unshielded.
Keep skin exposure to UV radiations to minimum.
Safety Techniques and Practices
Spraying Chromatograms
When strong corrosive and toxic reagents are sprayed on
chromatograms, use gloves, face shield, respiratory protection, and
appropriate fume removal device to protect skin, eyes, and respira-
tory tract against mists or fumes generated by spraying device.
Pipets
Do not pipet any liquids by mouth. Use pipet fillers or rubber tub-
ing connected through trap to vacuum line for this purpose.
Wet Oxidation
This technique is among the most hazardous uses of acids but can
be performed safely. Observe precautions in this chapter for partic-
ular acids used and rigorously follow directions given in specific
method.
Hazardous or After Hours Work
Anyone working alone after hours or on hazardous procedures
should arrange to be contacted periodically as a safety measure.
Glass Tubing
Protect hands with heavy towel or gloves such as those made of
Kevlar when inserting glass tubing into cork or rubber stopper.
Fire polish all raw glass cuts.
Open ampules in fume removal device over tray large enough to
hold contents if ampule should break. If contents are volatile, cool be-
fore opening.
Safe Handling of Concentrated Corrosi
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