Abstract: An inlet seal assembly for sealing an injection port member in a chromatography instrument , comprising an injection port member having a raised metal ring, an inlet seal member with an upper surface, a peripheral groove formed in the inlet seal member upper surface, a soft resinous plastic material ring positioned in the peripheral groove opposite the raised metal sealing ring, a reducing nut holding the inlet seal member against the injection port member, and threads connecting the reducing nut to the injection port member whereby to press the soft ring against the raised metal sealing ring to form a seal. The inlet seal assembly also may have a bottom seal between the inlet seal member and the reducing nut. A method of making and using the inlet seal assembly.