Sample valve for chromatographic apparatus

Claim 1

In chromatographic apparatus of the type comprising a separation column to which is connected a supply of carrier fluid to extablish a continuous flow thereof through the column, the apparatus further including a sample valve operable to inject into said flowing carrier fluid a precisely metered amount of a sample mixture to be separated into its constituent components by the column for detection and determination of the concentration of at least one component, said sample valve being of the type having first and second members with interaction surfaces slidably engaged for shifting movement between first and second positions, said members being formed at said interaction surfaces with first passage means cooperable in said first position to connect said carrier fluid supply to said column to establish said continuous flow of carrier thereto, said members being formed at said interaction surfaces with second passage means cooperable in said first position to connect a supply of sample mixture to a metering section to place therein a predetermined amount of sample mixture, with at least a part of said passage means being cooperable in said second position to entrain the sample mixture from said metering section into the flowing carrier fluid to be conducted through said column for analysis; the improvement in said apparatus wherein both said first and second members, including said interaction surfaces thereof, are made of a technical ceramic which is chromatographically inactive and which comprises metal oxide of at least 80 percent purity sintered to a dense mass at a sintering temperature of at least about 1,100* C and formed with said interaction surfaces having a smoothness effectively eliminating any adsorbent effect of the surfaces on the fluid samples.