PROBLEM TO BE SOLVED: To shorten whole analysis time including the pretreatments of a sample by a deproteinizing column provided for a sample injection part. SOLUTION: The sample injected from an injector 18 is guided to a deproteinizing column 16a, and sample components are trapped and concentrated. The sample components already trapped in a deproteinizing column 16b are eluted by a movable phase for analysis fed from liquid feeding units 6a and 6b, fed to a separating column 2, and detected by a detector 12. Then change- over valves 14a and 14b are simultaneously switched to channels of broken lines to pass the movable phase for analysis through the deproteinizing column 16a this time. The trapped sample components are eluted, guided to the separating column 2, and detected by the detector 12. The next sample is simultaneously injected from the injector 18 and fed to the deproteinizing column 16b while being diluted by a movable phase for sample injection.
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