| 摘要 |
A sample injector for a liquid chromatograph comprises a high pressure syringe unit (A) , a sample intake unit (B) having a needle (8) which can be introduced into a sample container (22) as well as a seat (9) , and a 6/2-way valve (C). The high pressure syringe unit is designed as a piston pump with a pump head (6) and a piston (5) which is driven by a motor (36) via a drive mechanism. Pressurized liquid from a solvent delivery system (SDS) can enter the pump head (6) through an inlet port (39) and flow along the piston (5) to an outlet port (40). When sample is to be injected into a chromatographic column, the 6/2-way valve is first switched into the position depicted by dotted lines, the needle (8) is introduced into the container (22) and the piston (5) is retracted by a corresponding distance. Thereafter, the valve is switched back to its original position so that solvent delivered from the solvent delivery system can transport the sample to the column. Since the solvent flushes the entire syringe unit, it is ensured that no sample residues remain in the syringe unit which would otherwise impair the chromatographic measuring process. |
