Available equipment

The material the needle and syringe are constructed from is an important consideration when considering their use. The reactivity of the chemicals to be transferred should be considered and if these are likely to react with either the needle or syringe, alternative methods for dispensing the liquids should be considered. Some syringes include rubber seals on the plunger which are particularly prone to reactions, especially from solvents (eg THF). Both syringes and needles are manufactured by a number of companies (predominantly for use within clinical environments). For convinience, disposable syringes and needles are most commonly used, although both parts can be purchased as reusable equipment.

The common consumables available within teaching labs are listed below. Predominantly Luer-slip syringe and needles are used, although some Luer-lock tipped syringes and needles are available.

Syringes

There are two main kinds of syringes available in the teahcing labs. The first of these are luer Slip syringes (pictured below on the left) which feature a push fitting where the needle hub just sldies onto the tip of the syringe. The second kind are luer lock syringes (pictured below on the right) where it is required to screw in the needle hub into the fitting to secure the needle. Specific information on the kinds of syringes we have are listed below but both kinds feature a two piece syringe/plunger combination manufactured from polypropylene and polyethylene.

Syringes are suitable for transferring volumes from around 0.1 mL to approximately 50 mL. 

Needles

BD Microlance disposable needles are available in a few combinations of gauge (diameter) and length given below. The needle is stainless steel with an epoxy resin luer slip tip.

For most liquid transfers, long needles are usually used, as this allows easy dispensing of reagents from bottles and the expelling of air (or gases) from the syringe as it can be inverted without having to remove the needle.

Safety

The needles used for drawing up liquids have a sharp tip which easily pierces skin. Care needs to be taken to avoid the risk of needle-stick injuries, especially when the needles have been used to draw up chemicals. Needles should be placed into sharps bins for disposal. Needles are provided packaged, with a sheath covering the needle to avoid injury. These can sometimes be hard to remove. They should be carefully slid off, and not forced. Once the sheath is removed, you should not attempt to resheath a needle, and this can easily lead to injury.

The most likely causes of injury with needles are:

• Removal of the syringe sheath with excessive force

• Resheathing needles

  • If you remove the protective cover from a needle, do not attempt to put it back in place

• Not holding the needle onto the syringe barrel when expelling contents from the syringe, resulting in the needle detaching and contents being sprayed from the syringe

• Disposal to anywhere other than a sharps bin

  • Do not leave needles lying around fume hoods and dispose immediately to a sharps bin

Related techniques

Using balloons are a useful technique for simple reactions and precipitation but are not always a feasible option, as some reactions (or reagents) require more rigorous handling. The next step from using balloons/needles to provide a better level of air/moisture excusion is to use a Schlenk line.

Schlenk lines

Unlike using balloons, which uses positive pressure to displace the air, Schlenk lines use a vacuum to remove the air before back-filling with nitrogen creating a totally inert atmosphere. The use of the vacuum along with greasing the glassware ensures that the reaction vessel is air-tight. You can find more information in the ‘Schlenk Lines’ section within air-sensitive techniques.