A method for the contamination-free transfer of liquid from a first container containing a volume of said liquid and at least an equal volume of gas to a second container containing at least a volume of gas equal to the amount of liquid that is to be transferred into it, said method comprising the steps of:
- (a) providing a fluid transfer apparatus comprising:
- a closed container having a moveable internal partition that divides the interior of said container into two separate fluid tight chambers having variable volume, wherein one of said chambers is a gas chamber and the other of said chambers is a liquid chamber;
- and a first segment of a gas channel and a first segment of a liquid channel, wherein the proximal ends of said first segments are in fluid communication with the interiors of said gas chamber and said liquid chamber respectively and the distal ends of said first segments are enclosed by sealing means;
- (b) providing a second segment of a gas channel and a second segment of a liquid channel, wherein the distal ends of said second segments are in fluid communication with the interior of said first container and the proximal ends of said second segments are enclosed by sealing means;
- (c) pushing the distal end of said first segments in the direction of the proximal end of said second segments until the distal ends of said first segments penetrate said sealing means at the distal end of said first segments, penetrate said sealing means at the proximal end of said second segments, and enter the proximal ends of said second segments, thereby providing a continuous gas channel between the interior of said first container and the interior of said gas chamber and a separate continuous liquid channel between the interior of said first container and the interior of said liquid chamber;
- (d) allowing an equilibrium to be established between the pressure of the gas in said first container and the pressure of the gas in said gas chamber and between the pressure exerted on the liquid in said first container and the pressure exerted on the liquid in said liquid chamber;
- (e) moving said internal partition in a first direction in order to increase the volume of said liquid chamber and instantaneously decrease the pressure inside said liquid chamber and simultaneously decrease the volume of said gas chamber and instantaneously increase the pressure of said gas inside said gas chamber, wherein the differences of pressure caused by moving said internal partition cause liquid to flow from said first container through said continuous liquid channel into said liquid chamber and an equal volume of gas to flow simultaneously from said gas chamber through said continuous air channel into said first container, wherein said flow of liquid in one direction and simultaneous flow of gas in the other direction continues until said internal partition stops moving and said equilibrium is reestablished;
- (f) disconnecting said first container from said fluid transfer device by pulling the distal ends of said first segments back out of the proximal ends of said second segments, through said sealing means at the proximal end of said second segments, thereby enclosing the ends of said second segments, and through said sealing means at the distal end of said first segments, thereby enclosing the ends of said first segments;
- (g) providing a third segment of a gas channel and a third segment of a liquid channel, wherein the distal ends of said third segments are in fluid communication with the interior of said second container and the proximal ends of said third segments are enclosed by sealing means;
- (h) pushing the distal end of said first segments in the direction of the proximal end of said third segments until the distal ends of said first segments penetrate said sealing means at the distal end of said first segments, penetrate said sealing means at the proximal end of said third segments, and enter the proximal ends of said third segments, thereby providing a continuous gas channel between the interior of said second container and the interior of said gas chamber and a separate continuous liquid channel between the interior of said second container and the interior of said liquid chamber;
- (i) allowing an equilibrium to be established between the pressure of the gas in said second container and the pressure of the gas in said gas chamber and between the pressure exerted on the liquid in said second container and the pressure exerted on the liquid in said liquid chamber;
- (j) moving said internal partition in a second direction in order to decrease the volume of said liquid chamber and instantaneously increase the pressure inside said liquid chamber and simultaneously increase the volume of said gas chamber and instantaneously decrease the pressure of said gas inside said gas chamber, wherein the differences of pressure caused by moving said internal partition cause liquid to flow from said liquid chamber through said continuous liquid channel into said second container and an equal volume of gas to flow simultaneously from said second container through said continuous air channel into said gas chamber, wherein said flow of liquid in one direction and simultaneous flow of gas in the other direction continues until said internal partition stops moving and said equilibrium is reestablished;
- and
- (k) disconnecting said second container from said fluid transfer device by pulling the distal ends of said first segments back out of the proximal ends of said third segments, through said sealing means at the proximal end of said third segments, thereby enclosing the ends of said third segments, and through said sealing means at the distal end of said first segments, thereby enclosing the ends of said first segments;
- said method characterized in that all of the liquid and the gas that flows between said fluid transfer device and said first container was present in either said fluid transfer device or said first container before said continuous liquid and gas channels between them were provided and all of the liquid and the gas that flows between said fluid transfer device and said second container was present in either said fluid transfer device or said second container before said continuous liquid and gas channels between them were provided.