About the cleaning of Plastic labware
Cleaning laboratory plasticware depends on the type and properties of the plastic.
Temperature in the form of extreme heat or cold affect flexability and strength.
Chemicals
such as lubricants and oil cause cracking, and prolonged use of oxidizing agents cause
brittleness and breakage.
Laboratory ware made with glass, quartz, polyethylene and polypropylene are subject to
interaction between container and sample,
or with reagents and standards and can give
incorrect results.
However, polyolefins and fluorinated hydrocarbons have excellent resistance to high
temperatures and chemical attack.
They have wettable surfaces and are easy to clean.
PFA Hydrocarbons
PFA has now become the plastic of choice for making laboratory plasticware. It has the
advantage of being formed by injection blow moulding. It therefore has high
transparency and ultrasmoothe surfaces that do not interact with analytes, reagents or
standards. It has excellent resistance to conc acids, alcohols, bases,
aliphatic/aromatic/halogenated hydrocarbons, ketones, mineral and vegetable oils. It is
ideal for trace analysis in low concentration determinations in ng/g and pg/g.
Cleaning methods
Acid bath
Immerse plasticware into a 1M nitric acid and allow to soak overnight
for mild contamination. Keep in bath for about one week for heavy contamination. The
cleaned plasticware is then taken out off the bath and rinsed with distilled water and put
to dry. A rinse with acetone or placement in a glassware dryer at low temperature can be
used.
Note: Plastics tend to float when put into the cleaning solution and can be sunk to the
bottom using a pair of tongs.
An acid bath is a container containing acid in which the
plasticware is placed and kept for some time until clean. The container should be made of
moulded plastic or pyrex glass with a loose fitting lid. The size and shape may vary
according to wash load and need.
Polyolefins and Fluorinated hydrocarbons
LPDE, HPDE, PP, PMP(TXP) and
PTFE, PFA, FEP, ETFE, E-CTFE
Slight contamination: Use a chemically neutral (pH 7) cleaning agent.
Heavy contamination: Remove using an alkaline (pH 12) cleaning agent.
Polycarbonate
Use only pH 7 neutral cleaning agents. Do not use alkaline cleaning agents.
Polystyrene
Use neutral cleaning agents only. Do not autoclave under any condition.
Note: Use only alcohols as solvent to remove greese and oils from PC and PS. Other solvents attack these plastics.
Polysulphonate
Never use cleaning agents containing tensiles (tween) for PSU.
Trace analysis
Soak in a 1:1 HCl acid bath for about 3 hours. Remove and then immerse for another 3 hours in a 1:1 nitric acid bath. Take out and rinse with distilled or deionized water. Dry as necessary.
Autoclave
Certain chemical contaminants on plasticware can be baked onto the plastic at autoclave temperatures.
Rinse thoroughly with distilled water before autoclaving.
Autoclave within the tolerated temperature range of the plastic being sterilized. Remove
any stoppers, caps or fittings before autoclaving.
Plastic containers such as vials, sample tubes and bottles should be autoclaved
with their closures disengaged to avoid deformation.
Note: Nylon, polyurethane, polystyrene, polyvinyl chloride (PVC), Acrylic, LPDE and HPDE
must not be autoclaved under any condition.
Reference:
E.I. Dupont & Co. Technical Literature
