Caring for your Plasticware Reprinted with permission of Nalge Nunc International General Cleaning Sterilizing Plastics Hazardous Matter Trace Level Cleaning Washing Plastics with a Mild Detergent is sufficient for most general applications. Be sure to rinse with tap water, and then rinse again with distilled water. Most plastics, particularly the polyolefins (PPCO, PP, PMP, LDPE, and HDPE), have nonwetting surfaces that resist attack and are easy to clean. Do not use abrasive cleaners or scouring pads on any plastic labware. Do not use strong alkaline cleaning agents with polycarbonate (PC). Labware Washing Machines can be used with most resins except acrylic, polystyrene (PS), and LDPE due to temperature limitations. PC will be weakened by repeated washings in dishwashers. PC labware exposed to high stresses (centrifuge ware, vacuum chambers) should always be washed by hand using mild, nonalkaline detergents. For PS, use a mild, neutral pH, nonabrasive, noncaustic detergent without sheeting agents. Set water temperature no higher than 135°F (57°C), and keep exposure as short as possible. Avoid excessive abrasion of plastics in dishwashers by covering metal spindles with soft material such as plastic tubing. Labware should be weighted down and held in place with accessory racks. Ultrasonic Cleaners can be used as long as labware does not rest on the bottom of the tank. Use a cleaning basket for best results. Removing Grease and Oils. Washing with a mild detergent will remove grease and oils in many situations. Another effective method is to boil labware in dilute sodium bicarbonate (NaHCO3). Do not use this method with acrylic, PC, PS, or LDPE. To remove grease and oils, you can use organic solvents (such as acetone, alcohols, or methylene chloride) with caution. Extended exposure to these solvents may cause polyolefins to swell. Rinse off all solvents before using labware. Use only alcohols on PC, PS, PSF, or PVC; other organic solvents attack these plastics. Do not use organic solvents with acrylic. Removing Organic Matter. Soaking plastic in a chromic acid solution will remove organic matter, but since it is a strong oxidizing agent, it will eventually embrittle plastics. To minimize embrittlement, soak for no more than 4 hours. To make the recommended chromic acid solution: Dissolve 120 g of sodium dichromate (Na2Cr2O7 - 2H2O) in 1000 mL tap water. Add 1600 mL concentrated sulfuric acid. Note: Because this solution generates considerable heat, we recommend external cooling. Do not mix in a plastic container. This solution produces an excess of dichromate in the precipitate form. It dissolves as needed, which extends the solutions life considerably longer than commercially available solutions. The solution can be used repeatedly until it begins to develop a greenish color, indicating a loss of potency. Sodium hypochlorite solutions (bleaches) are also effective at removing organic matter. Use at room temperature.
Autoclaving: Certain chemicals that have no appreciable effects on plastics at room temperature may cause deterioration at autoclave temperatures and therefore must be removed. To avoid baking these contaminants onto the surface of the plastic, carefully clean all items and rinse thoroughly with distilled water before autoclaving. Because of differences in heat transfer between plastics and inorganic materials, the contents of plastic containers may take longer to reach sterilization temperatures (typically 121°C). Thus, longer autoclaving cycles may be necessary for liquid contents. Cycle lengths can be determined only by experience with specific liquids and containers. Do not autoclave containers (except those made of fluoropolymers) containing detergent or wetting solutions. Note: Before autoclaving, just set cap or closure on top of the container without engaging threads. Polypropylene (PP), polypropylene copolymer (PPCO), polymethylpentene (PMP), Tefzel® ETFE, and FEP and PFA can be autoclaved repeatedly at 121°C/15 psi. Cycle length should be at least 15 minutes at 121°C to ensure sterility. Polysulfone (PSF) and polycarbonate (PC) are autoclavable, but can be weakened by repeated autoclaving. If autoclaved repeatedly, PSF will eventually fail under high-stress applications. After repeated autoclaving, PC shows some loss of mechanical strength and may not function well under high-stress applications such as centrifugation. Limit PSF and PC autoclave cycles to 20 minutes at 121°C. Polystyrene (PS), polyvinyl chloride (PVC), nylon, acrylic, low-density polyethylene (LDPE), and high-density polyethylene (HDPE) labware and polyurethane tubing are not autoclavable under any conditions. Note: Some transparent plastics may absorb minute amounts of water vapor and appear cloudy after autoclaving. The clouding will disappear as the plastic dries. Gas Sterilization: All of the resins mentioned on this page can be gas sterilized (ethylene oxide, formaldehyde). Allow an appropriate aeration time suited to the particular application before using the item. Chemical Disinfectants: In general, all of the plastics mentioned on this page can be subjected to commonly used disinfectants (formalin, iodophors, quaternary ammonium compounds, benzalkonium chloride). There may be some surface attack (crazing) when using a more chemically aggressive disinfectant for a prolonged time on the less chemical resistant plastics (acrylic, PS, PC, PVC). Dry Heat: Recommended only for ECTFE, Tefzel® ETFE, FEP and PFA, PMP, PSF, and TFE. Maximum temperatures and minimum sterilization times at each temperature are given in the following table: | Dry Heat Sterilization | | Resins | Temperature | Time | | FEP and PFA, PMP*, TFE | 170°C (338°F) | 60 min | | PSF | 160°C (320°F) | 120 min | | ECTFE, Tefzel® ETFE | 150°C (302°F) | 150 min | *with no load, no stacking Microwaving: In general, all plastics allow transmission of microwaves. Among commonly used plastics, PMP and PSF are most transparent to microwaves; we recommend their use when the chemical and temperature resistance of PMP and PSF are compatible with the material to be heated. Use fluoropolymers when heating aggressive chemicals such as acids or solvents; proper ventilation is essential.Note: Closure threads must be completely disengaged before heating bottles or containers in a microwave oven.
For Labware Contaminated with Infectious or Toxic Materials, autoclaving is the preferred method for sterilization. However, any method of chemical or heat sterilization compatible with the plastic can be used. Liquid waste that contains biohazardous materials must be decontaminated before disposal. For Labware Contaminated with Both Biohazardous and Radioactive Material, first sterilize the labware, then remove the radioactive material. Methods for removing radioactive material depend on the isotope used, its quantity, half-life, material, and solubility. For routine decontamination of noninfectious/nontoxic labware, first soak in a decontaminant/cleaner for 24 hours at room temperature. Follow this with several rinsings in distilled water. To accelerate decontamination, increase the cleaner concentration and solution temperature. Always dispose of radioactive wastes and effluents properly.
For Most Trace Metal Analyses, plastic is generally less contaminated than glass or other materials. However, plastic does contain trace levels of certain metals. To minimize potential low-level contamination, remove or leach these metals from plastic by soaking in 1N HCl and rinsing in distilled water. For more precise work, use HCl, followed by soaking in 1N HNO3 and rinsing in distilled water. Soaking time can vary according to individual needs, but plastics should not be soaked longer than 8 hours. Caution: Concentrated nitric acid is a strong oxidizing agent and will embrittle many plastics. To Remove Trace Organics that contribute to trace metal absorption, clean plastic surfaces with alcohol, alkalies, alcoholic alkalies, or chloroform. A final rinse of 1N HCl also minimizes absorption of trace elements. |
