Many liquid reagents are air stable, and therefore come packaged in regular bottles. These bottles result in the compound being open to the air when the lid is removed.

In order to add liquid reagents packaged in this form into reactions being carried out under inert conditions, a modified approach for syringing these reagents needs to be employed. 

The key differences are:

• The absence of a septum means the syringe is not held in place during the drawing up

• After the liquid has been drawn up and measured, no additional gas bubble should be drawn into the syringe, as this would be atmospheric air

The guide linked below should be followed for the steps for purging the syringe, then the steps at the bottom of this page should be followed for the drawing up and addition of liquids.

• Ensure the bottle is securely clamped in place or held so that the bottle cannot tip over during dispensing.

• At this stage of drawing up, the syringe should be filled to a greater volume than the volume required.

• The excess amount varies depending on syringe size, but typically drawing up around 20% extra is a reasonable rule of thumb.

As the liquid is drawn into the syringe, a gas bubble will form above the liquid. This comes from the dead-volume in the syringe and needle, which will have been flushed with nitrogen, with this gas now being drawn into the syringe ahead of the liquid. It is also quite common to draw in some air whilst drawing up liquid from the reagent bottle, particularly if the needle is not very deep within the liquid.

• The bubble will need to be displaced to enable the accurate measurement of the liquid volume. This is acheived by displacing the bubble through inversion in the same manner as for reagents packaged under inert gases, but with some additional considerations.

• As the needle is not securely held in the bottle, the flexing of the needle needs to be carried out whilst holding the needle to ensure that the needle remains in the bottle. If the needle comes out of the bottle it is liable to flick, and could result in a needlestick injury.

• The needle inversion also puts pressure on the bottle. For small bottles this could easily result in the bottle being knocked over if the bottle isn't securely clamped or otherwise held in place.

• Hands should be positioned such that one hand is securing the needle in the bottle and securing the needle/syringe joint. The other hand should be holiding the barrel of the syringe, ready to expel the nitrogen bubble.

• The syringe is lowered by flexing the needle, taking care to ensure the needle is securely held within the flask. The syringe should be lowered until it is fully inverted alongside the flask or reagent bottle.

• Once the gas bubble has been expelled, the excess volume can then be returned to bottle. In order to read the measurements, the syringe graduations will need to be facing you.

• For Luer lock syringes, you cannot twist the needle in the syringe, as this would loosen the connection of the needle in the Luer lock. If the syringe needs repositioning, this needs to be achieved by returning the syringe to the vertical and flexing the needle again such that the markings are towards you.

• For Luer slip, the syringe can be carefully rotated in the needle without detaching the needle and syringe from each other.

• In both cases care needs to be taken to ensure the needle remains fully within the reagent bottle as any liquid is expelled from the syringe.

• Holding the needle and the needle/syringe joint in one hand and using the other hand to depress the plunger, any excess liquid can be returned into the bottle.

To transfer the liquid, the needle syringe need to be removed from the solvent flask and inserted into the reaction flask. Unlike with reagents provided under nitrogen, no gas bubble is drawn into the syringe prior to transfer, as this would be air, which would end up in the reaction flask.

• The needle/syringe connection should be held between thumb and forefinger with the rest of the same hand holding the syringe.

• The other hand should carefully hold the needle close to the end. The needle should then be removed from the bottle, keeping the syringe inverted and the needle forming an 'n' shape. Care needs to be taken to avoid the needle flicking as the needle is withdrawn from the mouth of the open bottle.

• The syringe needs to remain inverted during transfer.

Unlike reagents transferred under an inert gas, there is no gas bubble to be expelled before addition of the liquid, and can therefore be added immediately as the correct volume will be transferred. The needle should be guided through the septum into the reaction flask. Ensure the needle is sufficiently inserted into the flask before the liquid is dispensed.

Consider any specific instructions for the liquid addition, such as if the liquid needs to be added dropwise.

• Expel the liquid into the reaction flask.

• The syringe does not need to remain inverted during liquid addition.