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How much pressure or vacuum can your bottles and tanks withstand?
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NALGENE 2126-series Heavy Duty Polypropylene bottles are designed and rated to
withstand a full vacuum. No other NALGENE containers or tanks are rated for
pressure applications.
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Which plastics are resistant to UV radiation?
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UV radiation is commonly used in germicidal lights in hoods and is a component
of sunlight. UV radiation will have a serious deleterious effect on most
plastics, especially the polyolefins, including polyethylene (low-density
polyethylene [LDPE] or high-density polyethylene [HDPE]); polypropylene (PP),
and polymethylpentene (PMP); and acrylics. Polystyrene (PS), polycarbonate (PC)
and polyethylene terephthalate G copolymer (PETG) can withstand limited UV
exposure. In general the effects of UV can be seen as a color change, usually a
darkening or yellowing, combined with an embrittling effect.
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Why can’t I submerge NALGENE or NUNC cryogenic vials in liquid nitrogen?
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Actually, if you read the instructions carefully, you should not submerge any
brand of cryogenic vials into liquid nitrogen. This is because of the effect
the extreme cold of the liquid nitrogen has on plastics. There is significant
shrinkage and embrittling of plastics at cryogenic temperatures, which makes
any sealing system ineffective against liquid nitrogen. Liquid nitrogen also
has a relatively low surface tension, which makes it easier to seep into the
vial. So there is currently no screwtop cryogenic vial on the market today that
can claim to be leakproof in liquid nitrogen. Once liquid nitrogen has gotten
into the vial, there is a significant risk that the vial will explode during
thawing, in addition to the potentially deleterious effects of the liquid
nitrogen on the sample. That is why Nalge Nunc International offers CryoFlex
Tubing, which forms a complete seal around the cryogenic vial and prevents
liquid nitrogen from getting inside. We also recommend vapor-phase storage only
in liquid nitrogen freezers such as Locator Dewars from Barnstead/Thermolyne.
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What plasticizers are used in NALGENE plastics?
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Not all plastics contain plasticizers. Only NALGENE polyvinyl chloride (PVC)
Tubing and PVC Bottles contain plasticizers, mostly dioctyl phthalate (DOP).
All other NALGENE plastics are free of plasticizers.
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What is meant by durometer of tubing?
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Durometer is a measure of a material’s resistance to indentation, or
flexibility. Two scales are commonly used: Shore A for more flexible tubing
materials, such as PVC; and Shore D for semi-rigid materials, such as
Polypropylene. The higher the durometer number, the less flexible the material.
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Which plastics can I autoclave?
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Polypropylene (PP) and polypropylene copolymer (PPCO) products can be
autoclaved many times. We have PP containers in our lab that have been
autoclaved over 100 times and, although they have yellowed somewhat, they are
still in service.
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Fluoropolymer products, i.e., products made of Teflon PFA, FEP or ETFE, can all
be autoclaved without problems, except for the stopcocks in NALGENE Separatory
Funnels, which should not be autoclaved because of resultant leakage problems.
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Polycarbonate (PC) products can be autoclaved with caution; they should not be
exposed to alkaline detergents or steam additives, and they may withstand only
up to 30-50 autoclaving cycles, depending on the use.
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When autoclaving NALGENE bottles and carboys, be sure to completely disengage
the closure from the bottle threads OR use a carboy vent, such as the new
NALGENE Carboy Vent Filter, cat. no. 223-0020. This is necessary because the
leakproof NALGENE sealing system does not allow venting, which can cause these
containers to collapse during the exhaust cycle.
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Which centrifuge tube can I use for DNA precipitaitons?
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The best material for repeated use is Teflon FEP, which can easily withstand
the phenol or alcohol precipitaitons commonly used for nucleic acids. PPCO
tubes can be used with cold alcohol precipitaitons.
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What plastic has the most/least protein binding?
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There is no easy answer to this question. Protein binding is a complicated
phenomenon that is affected by many variables including temperature, pH and the
presence of other proteins, salts or surfactants. In general, we can say that
the polyolefins (LDPE, HDPE, PP) and the fluoropolymers will bind fewer
proteins than PS, PETG or PC.
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What extractables/leachables are present in plastics?
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This is a very complicated issue. Most of the potential extractables from
plastics are actually additives in the plastic. Common additives include
stabilizers like BHT; lubricants like calcium or zinc stearates, colorants. It
is common for these additives to include both organic and inorganic components.
There may also be some monomer of the plastic available for extraction in the
final molded product. These extractables typically occur in very low
concentrations (ppm or ppb). For any of these extractables to actually leach
into a fluid, however, the following criteria must be met: 1) the extractable
must be on the surface of the plastic to be in contact with the fluid, and 2)
it must be soluble in the fluid. So, even though a plastic contains an
additive, it may not be extractable in a particular fluid.
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What membrane filter pore size should I use for sterilization, and what’s
the pore size of my fiber prefilter?
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Regardless of the material, always use a 0.2-um pore size membrane filter as
the final filter for any sterilization filtration.
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Fiber prefilters do not actually have a measurable pore size rating because
they are depth filters. We rate the prefilters with a relative retention of
about 1.0-um size particles for general purpose prefiltration applications.
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