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Engineering safer syringes

Perfektum syringe clip

Perfektum syringe clip

Last fall, C&EN ran a couple of letters that focused on the role of the syringe in the #SheriSangji case. Both called for a way to prevent a syringe plunger from coming out of the barrel. I’ve seen mention of such devices in comments around the web in the last few years, so I thought I’d take a look at what I could find:

1. The Hamilton Chaney adapter, “a device that assures repetitive and identical syringe plunger location.” The maximum volume syringe appears to be about 500 microliters, and it’s not clear how much force these adapters would resist.

2. Perfektum syringes go up to 100 mL and have a little metal clip on the end that puts pressure on the barrel. A kind source had one in their lab and took the photos to the right for me. The clips look like they wouldn’t resist much force.

Perfektum syringe clip on syringe

Perfektum syringe clip on syringe

3. Valco VICI precision syringes, which have a “positive rear flange plunger stop – prevents plunger from blowing out of barrel at elevated pressure.” They’re designed for chromatography. I have no idea how the plunger stop works. Readers?

4. As one of the letter-writers noted, Becton Dickinson has patents issued in the mid-90s for syringes with “a backstop device to prevent inadvertent withdrawal of a stopper or plunger rod” and “a plunger brake.” These look promising but as far as I can tell neither is available on any syringe available for purchase.

5. For the do-it-yourself crowd, an option is to drill a hole into a plastic syringe barrel and put in a screw far enough to serve as a brake on the plunger. (This procedure, of course, comes with its own set of risks.)

To sum, I really see no readily available answer for the problem. Am I missing something?

4 Comments

  • Feb 8th 201308:02
    by Ken

    Option 5 looks the best to me. The syringes in options 1 and 3 are expensive, requiring that they be disassembled and cleaned after use. The plunger stops in option 3 work just fine, however.

    The Perfektum syringes should never be used with lithium reagents or similar materials (Grignards, aluminum alkyls, etc). In fact, they should be banned from use with pyrophorics or highly reactive and flammable materials. The glass on glass barrel/plunger is very prone to seizing with these syringes. I venture to guess that they were designed to syringe aqueous solutions, and that is all they should be used for. BTW, the clip shown looks like it is designed to keep the plunger from falling out when the syringe is held in a vertical orientation with the plunger on the low side due to gravity, not to prevent the plunger from being actively pulled out during use.

    Rigging a disposable plastic syringe (PE/PP only, no rubber tipped barrels!) with a stop akin to the description above is very inexpensive, simple, and accomplishes the task. After one draw/injection just throw the syringe away and don’t risk a problem during cleaning. A pack of 10 mL syringes from Aldrich costs just under $0.50 per syringe.

  • Feb 8th 201315:02
    by silane

    Perfektum syringes have been used for years and when used properly are effective tools to transfer small amounts of air-sensitive reagents (pyrophoric or water reactive). I was trained to use them a long time ago and they are not that bad. I have only had them seize once but that was entirely my fault for doing something stupid. Yes the clip is to provide a correction for gravitational forces and nothing more but by definition that would be “…a way to prevent a syringe plunger from coming out of the barrel.”

    People make mistakes. The idea of safety is proper training and layers of protection. The purpose of training is to know what to do when you make a mistake and you will make mistakes. The layers of protection are so that when you have that spill the amount of danger you are in is limited. Work in a clean hood. Work behind a sash. Ware a lab coat. Pull the plunger parallel to you, not perpendicular. Etc.

    I am not fond of technology to prevent you from pulling out the plunger. It can give you a false sense of security and complacency is a bad thing. I would suggest that canula transfer is the safest way to transfer air-sensitive material. I only use syringes if my volumes are small (10mL) or if I am feeling particularly lazy. I only have 3 canulas clean at any particular time but I have a drawer full of syringes. Disposable or not you still need to clean the syringe after you use it. It would be a bad idea to leave active material in any syringe.

  • Mar 7th 201319:03
    by orbitals

    I have to agree that it is better to use a cannula to transfer larger amounts of dangerous liquids – it’s much less prone to difficulties. In any case, organics should never be handled in plastic syringes, though they work fine with aqueous materials or with anything where care and purity are of no concern (I use them for getting epoxy into tight spots in cabinet making or for dispensing lubricants at home). Even if you think you have identified a solvent system that will be safe for short-term exposure with plastic you will find yourself bedeviled by problems with extractables. Ask someone to whom it has happened what it feels like to isolate a nice clean sample of a plasticizer 10, 20 or more steps into a multistep synthesis (the many comments that plastic syringes often require a lot of force to pull the plunger, which also makes it easy to inadvertently pull the plunger out are also true – this would not happen with a proper glass syringe). Also, neither I nor anyone I’ve trained has ever had any trouble with a properly matched and maintained glass syringe “freezing.” My heart just ached when I saw the photo in C&EN of the inappropriate, makeshift rig used by Ms. Sangji when she was killed while trying to transfer t-butyllithium. It would have been astonishing if she had not experienced any difficulties.

  • Mar 8th 201310:03
    by Mark Williams

    If you are using a substance that can generate it’s own pressure inside the syringe, you should not be using a syringe. If you trap the plunger so that pressure cannot be relieved by blowing out the plunger, then the syringe may explode.

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