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What are other pros and cons of each? What do you use each for?
Discussions about GC and other "gas phase" separation techniques.
lkochraney wrote:
Naturally, choice is up to the end user and instrument requirements. Some instruments require magnetic seals, and unless there has been a recent introduction of a magnetic screw cap vial in a 1-2mL volume, crimp vials would be required.
As for sealing properties, if sealed properly, I see no advantage of one over the other.
One disadvantage of crimp seal vials is the variation in the depth of the vial opening lip, which is the location of the seal. Septa thickness varies as well; therefore, to reduce or eliminate problems with making a proper seal, use an adjustable crimper.
Screw cap vial are easier to use; however, if the cap is screwed on too tight, the septa stretches creating resistance to the needle, possibly bending the needle. If the threading tool used during manufacturing of the vial has worn down and not noticed right away, threads are distorted, resulting in the cap not fitting properly. If caps are washed and dried at high temperature for reuse, they eventually dry out. This can be dangerous when screwing the cap onto the vial. The cap may break, possibly breaking the vial neck, resulting in the possibility of a hand injury.
If one wants to store samples and have better protection against degradation, and/or loss of sample due to pierced septa, use of a Mininert Valve has two lines of defense. It has an open/close valve and septa in the cap. This valve is very useful when storing standards. When searching for vial valves, such as the Mininert type, pay close attention to the thread type. Not all vials of the same volume, such as 2mL Micro Reaction vials, have the same thread size as standard vials. Match the thread size, not vial volume.
Linda
mariosapm wrote:
... The screw top vials are easier to use.
...
Yama001 wrote:
My understanding is the Mininerts were not designed to seal well in the freezer. They are great for a working standard for daily usage.
For long term, I would not trust any vial with an open cap and septum, crimped or not. Solid screw on cap with little or no headspace has been the most trustworthy in my experience.
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