An automated sampler for sampling contaminants that are dissolved in water. An empty, sealed first vial is placed at a first sampling station with a dual-port needle, and a mechanical syringe pump displaces a programmable volume of gas from the first vial. A sealed second vial having a field sample of water with dissolved contaminants, typically without a headspace region, is placed at a second sampling station, with a dual-port needle. The syringe pump extracts an aqueous volume from the second vial, then transfers the aqueous volume into the first vial. This is all done without exposing the field sample to any external gasses or other compounds, and without opening the seal of the field sample to atmosphere. The sample in the first vial is heated, and an aliquot of headspace from the first vial is then injected into an analyzer device for identification and quantification.