Liquid measuring device

1. A liquid measuring device that measures a fixed volume of liquid comprising:

a first barrel having a proximal and distal end;

a coupling device comprising a gas or vapor permeable but liquid impermeable barrier on a second barrel, said second barrel being movable along said first barrel to adapt said barrier to the measuring device, whereby the fixed volume of liquid is adjusted by moving said coupling device along said first barrel by means of a screw;

a gas, vapor and liquid impermeable element adapted to the measuring device to provide a pressure difference between two sides of said barrier such that the liquid can only be filled from said distal end of said first barrel up to said barrier; and

a valve at said distal end.

2. The liquid measuring device of claim 1 , wherein the volume in said first barrel up to said barrier equals the fixed volume.

3. The liquid measuring device of claim 1 , further comprising a holder to position and secure said coupling device in the liquid measuring device.

4. The liquid measuring device of claim 1 , which is a syringe.

5. The liquid measuring device of claim 1 , which further comprises a third barrel which is in fluid communication with said first barrel by means of a valve.

6. The liquid measuring device of claim 1 , wherein said gas or vapor permeable but liquid impermeable barrier comprises hydrophobic material.

7. A method of measuring a fixed volume of liquid comprising:

(a) providing a device comprising:

(i) a first barrel having a proximal and distal end;

(ii) a coupling device comprising a gas or vapor permeable but liquid impermeable barrier which is movable along the first barrel to adapt the barrier to the measuring device, whereby the fixed volume of liquid is adjusted by moving the coupling device along the first barrel by means of a screw; and

(iii) a gas, vapor, and liquid impermeable element adapted to the measuring device to provide a pressure difference between two sides of the barrier such that the liquid can only be filled from the distal end of the first barrel up to the barrier;

(b) moving the gas or vapor permeable but liquid impermeable barrier along the first barrel to adjust the fixed volume;

(c) filling a volume formed by the distal end of the first barrel to the barrier with liquid wherein the volume is equal to the fixed volume; and

(d) closing a valve after filling the device.

8. The method of claim 7 , wherein the coupling device comprises a second barrel and the barrier is on the second barrel.

9. The method of claim 8 , wherein moving the gas or vapor permeable but liquid impermeable barrier along the first barrel is by changing the relative position of the first barrel to the second barrel.

10. The method of claim 7 , further comprising securing the coupling device to the first barrel.

11. A liquid measuring device configured to measure a fixed volume of liquid, the measuring device comprising:

a barrel;

a gas or vapor permeable but liquid impermeable barrier, wherein said barrier is movable relative to said barrel;

a screw adjustment member configured to move said barrier relative to said barrel; and

a plunger configured to be moved relative to said barrel to draw the fixed volume of liquid into said barrel up to said barrier.