A device for sampling fluid from an earth formation is disclosed. The device includes: an inlet port disposable in fluid communication with the fluid in a borehole; an injector including an injection chamber in fluid communication with the inlet port, the injector configured to receive a portion of the fluid and direct the fluid toward an analysis unit for analyzing constituent materials in the fluid; and a high pressure valve configured to admit the portion of the fluid at a borehole pressure and release the portion of the fluid into the injector, the portion having a volume that is less than or equal to about one microliter. A system and method for analyzing constituents of fluid in a borehole in an earth formation is also disclosed.