FAQs: Thermo Scientific Nalgene Labware
How much pressure or vacuum can your bottles and tanks
withstand?
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.
Which plastics are resistant to UV radiation?
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.
Why can’t I submerge NALGENE or NUNC cryogenic vials in
liquid nitrogen?
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.
What plasticizers are used in NALGENE plastics?
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.
What is meant by durometer of tubing?
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.
Which plastics can I autoclave?
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.
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.
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.
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.
Which centrifuge tube can I use for DNA precipitaitons?
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.
What plastic has the most/least protein binding?
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.
What extractables/leachables are present in plastics?
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.
What membrane filter pore size should I use for
sterilization, and what’s the pore size of my fiber
prefilter?
Regardless of the material, always use a 0.2-um pore size
membrane filter as the final filter for any sterilization
filtration.
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. |
