Fluid sample holders with piston valve

A fluid sample holder suitable for allowing a fluid sample to be delivered to, or received from, fluid processing equipment, the sample holder comprising:

• a sample fluid reservoir;
• a sample fluid port for providing fluid communication between said sample fluid reservoir and said fluid processing equipment;
• a buffer fluid port also for providing fluid communication between the reservoir and the fluid processing equipment;
• and a sliding seal within the reservoir including a sealing area which generally sealing engages with a wall of the reservoir thereby defining a first and a second fluid separated region in the reservoir, said first region being in fluid communication with the sample fluid port, and said second region being in fluid communication with the buffer fluid port, said sliding seal being displaceable within the reservoir by means of a pressure differential between said first and second regions to thereby change the respective volumes of the first and second regions, and the sliding seal including a valve operable when the sliding seal reaches or substantially reaches an end of its displacement, said valve including a stem having a tapered portion for cooperating with a complementary tapered aperture for substantially preventing fluid flow when so cooperating, said stem being displaceable away from said aperture and out of said cooperation at said end of its displacement, to open the valve.