Fully automated micro-autosampler for micro, capillary and nano high performance liquid chromatography

An autosampler for use in liquid chromatography comprising:

• a sample aspirating device, a low pressure valve, a transfer tube, a multiport injection valve with an electronically time-controlled valve switch, a sample intake tube, a needle, means for translocating said needle, means for translocating said intake tube, and a chromatographic column;
• wherein said aspirating device and said transfer tube are in low pressure valve-regulated liquid communication, said intake tube and said transfer tube are in injection valve-regulated liquid communication, and said intake tube is concentric with and internal to said needle,
• wherein said needle translocating means introduces said needle into a septum-covered container, said intake tube translocating means slides said intake tube through said needle into said container without contacting said septum,
• wherein said aspirating device transfers less than about 5 .mu.L of said sample into and through said sample intake tube to said injection valve, whereby said sample separates into more dispersed and less dispersed portions;
• and,
• wherein said valve switch directs said less dispersed portion to said chromatographic column and diverts said more dispersed portion from said chromatographic column, wherein the time at which the injection valve is switched back to a load position and injection is terminated, the switching time S.sub.t is calculated using the formula:
• S.sub.t =f.times.V.sub.inj .times.60/F
• where f is a low-dispersion factor, V.sub.inj is the desired sample injection volume in microliters, and F is the volumetric flow rate in microliters per minute.

A method for automated sampling of a portion of a liquid sample for liquid chromatography, said sample contained in a septum-covered sample container, said method comprising steps:

• a) inserting a sharpened tip of a needle comprising a bore through said septum and into said container,
• b) translocating a sample intake tube comprising a terminus through said bore from a first position wherein said intake tube terminus is recessed within said needle to a second position wherein said terminus protrudes from said tip and into said sample,
• c) aspirating a measured aliquot of less than about 5 .mu.L of said sample into said intake tube to form an injection plug of said sample;
• d) transferring said injection plug to a time-controlled multiport injection valve whereby said injection plug separates into more dispersed and less dispersed portions;
• and,
• e) switching said valve whereby said less dispersed portion is directed to a chromatographic column and said more dispersed portion is diverted from said chromatographic column, wherein the time at which the injection valve is switched back to a load position and injection is terminated, the switching time S.sub.t is calculated using the formula:
• S.sub.t =f.times.V.sub.inj .times.60/F
• where f is a low-dispersion factor, V.sub.inj is the desired sample injection volume in microliters, and F is the volumetric flow rate in microliters per minute.